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BMS2042 > Gene Interaction > Flashcards

Gene Interaction Flashcards

1
Q

How do chromosomes pair up during meiosis in tetraploids?

A

Two bivalents or one quadrivalent

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2
Q

Define recombination frequency

A

a measure of genetic linkage and is used in the creation of a genetic linkage map. Recombination frequency (θ) is the frequency with which a single chromosomal crossover will take place between two genes during meiosis

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3
Q

Define

Barr body

A

the inactive X chromosome in female somatic cells

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4
Q

True or False:

The chromosomal complement of autotriploids is balanced

A

True

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5
Q

Why are autosomal aneuploids higher in older mothers?

A

In human females, meiosis begins in the foetus but arrests at the diplotene stage of prophase I.

Meiosis only recommences when the egg is released at ovulation

As egg ages up to 45 year, chance of nondisjunction increases potentially due to spindles being less efficient with age of the cell

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6
Q

How do you calculate genotype frequency?

A

Number of individuals with genotype divided by total population number multiplied by 100

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7
Q

Why is it useful to generate genetic maps?

A

To determine whether mutations affect different genes or not To clone genes using their map position To enhance our ability to predict inheritance patterns Very useful for genome sequencing projects

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8
Q

A Drosophila has the sex complement XXY. What is it’s sex? Is it viable? Is it fertile?

A

Female

Viable

Infertile

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9
Q

Definition

a genetic condition in which a male has an extra Y chromosome. Symptoms are usually few. They may include being taller than average, acne, and an increased risk of learning problems

A

Double Y syndrome

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10
Q

Define coupling phase

A

a phase in which the dominant alleles of two or more genes present in the same chromosome and hence linked to­gether. Dominant alleles are contributed by the same parents.

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11
Q

True or False:

Most trisomy 21 babies do not live to term

A

True

80% do not successfully come to term

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12
Q

Define acrocentric

A

A chromosome in which the centromere is located quite near one end of the chromosome

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13
Q

Definition

the first step in X inactivation where the X inactivation centre (Xic) of one of the X chromosome is initiated by the expression of the gene XIST

A

Initiation

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14
Q

How do you calculate recombination frequency?

A

RF = Number of recombinants / Total progeny x 100

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15
Q

Definition

the final step in X inactivation where the inactivation is maintained by continued XIST expression in the Barr body in interphase

A

Maintenance

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16
Q

Definition

a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology

A

Population genetics

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17
Q

Definition

a branch of genetics that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis

A

Cytogenetics

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18
Q

If an individual is homologous for an inversion, what happens during meiosis?

A

Meiosis proceeds as normal

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19
Q

What is this an example of?

A

Nonreciprocal translocation

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20
Q

What is an example of a biochemical polymorphism?

A

Alcohol dehydrogenase allozyme

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21
Q

Define positive interference

A

the phenomenon that the occurrence of a crossover reduces the probability of another crossover in its vicinity

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22
Q

What is the effect of mitotic nondisjunction?

A

A permanent change in all descendant cells leading to a mosaic

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23
Q

Define

Copy number variation

A

a phenomenon in which sections of the genome are repeated and the number of repeats in the genome varies between individuals in the human population

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24
Q

Define

Giemsa stain

A

a stain that labels the phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of adenine-thymine bonding. Giemsa stain is used in Giemsa banding, commonly called G-banding, to stain chromosomes and often used to create a karyogram

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25
Q

Definition

The chromosomal variation in the normal complete set of chromosomes in a cell or an organism resulting in a multiple of the haploid or basic number of chromosomes

A

Euploid

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26
Q

Definition

a chromosome formed by three homologous chromosomes that lie close together or appear to join completely during meiosis

A

Trivalent

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27
Q

What are the male and female sex chromosome system in Drosophila ?

A

F: XX

M: XY

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28
Q

What is a somatic cell hybrid?

A

Somatic cell hybrids are formed through fusion of different somatic cells of the same or different species. Somatic cell hybrids contain the nucleus of both cells and in addition all cytoplasmic organelles from both parents

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29
Q

Define

Population

A

a group of organisms of a species that interbreed and live in the same place at a same time

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30
Q

Roughly how many crossovers occur in an average human chromosome at each meiosis?

A

2-3 crossovers

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31
Q

When there is no gain or loss of genetic material, what type of rearrangement is it?

A

Balanced

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32
Q

Very small numbers in the size of a population (bottlenecks) can lead to:

a) all individuals migrating to a new environment
b) natural selection against unfit individuals
c) mutation of A to a, and of a to A
d) genetic drift

A

d) genetic drift

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33
Q

What is this an example of?

A

Duplication

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34
Q

A Drosophila has the sex complement X. What is it’s sex? Is it viable? Is it fertile?

A

Male

Viable

Infertile

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35
Q

Define

Trisomy

A

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities

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36
Q

True or False:

Autotriploids are viable but not fertile

A

True

(due to unbalanced gametes)

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37
Q

Definition

a congenital disorder arising from a chromosome defect, causing intellectual impairment and physical abnormalities including short stature and a broad facial profile. It arises from a defect involving chromosome 21, usually an extra copy (trisomy-21)

A

Down syndrome

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38
Q

What gametes are produced in nondisjunction II in males?

A
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39
Q

Define short tandem repeat (STR)

A

another name for a microsatellite

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40
Q

Definition

regions on the X and Y chromosomes where crossing over occurs exhibiting autosomal, rather than sex-linked, pattern of inheritance

A

Pseudo-autosomal

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41
Q

Definition

variant forms of an enzyme which differs structurally but not functionally from other versions coded for by different alleles at the same locus

A

Allozymes

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42
Q

Define loci

A

a fixed position on a chromosome, like the position of a gene or a marker

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43
Q

Define

Euploid

A

The chromosomal variation in the normal complete set of chromosomes in a cell or an organism resulting in a multiple of the haploid or basic number of chromosomes

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44
Q

What are the possible gametes for a paracentric inversion with a crossovers within the inverted region?

A
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45
Q

Definition

the conformation of pairing up of homologous chromosomes in meiosis that are heterozygous for inversions

A

Inversion loop

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46
Q

Define interference

A

the term used to refer to the non-random placement of crossovers with respect to each other during meiosis

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47
Q

Define

Oogenesis

A

the production or development of an ovum

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48
Q

What are the possible gametes of a pericentric inversion with no crossover within the inverted region?

A
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49
Q

Definition

the existence of two different forms (as of color or size) of a species especially in the same population

A

Phenotypic dimorphism

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50
Q

How does false exclusion occur in DNA profiling?

A
  • Technical problems such as ‘allele drop-out’
  • Contamination or mixed source of DNA
  • Human error
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51
Q

Definition

a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13

A

Patau syndrome

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52
Q

Definition

the condition of having a diploid chromosome complement in which one chromosome lacks its homologous partner

A

Monosomy

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53
Q

Definition

a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is useful for identifying genetic diseases through the photographic representation of the entire chromosome complement. Also known as Giemsa banding

A

G-banding

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54
Q

Which gene determines maleness?

A

SRY

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55
Q

How do ring chromosomes form?

A
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56
Q

Why might autotriploids be desirable in plants?

A

They are sterile so they do not produce seeds (i.e. bananas)

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57
Q

Define

Robertsonian translocation

A

the most common form of chromosomal rearrangement where the participating chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere

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58
Q

Define

Hardy-Weinberg principle

A

a principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors

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59
Q

Definition

a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value

A

Stabilising selection

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60
Q

Definition

an event that drastically reduces the size of a population producing a decrease in the gene pool of the population because many alleles, or gene variants, that were present in the original population are lost

A

Bottle neck

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61
Q

Define

Polyploidy

A

the state of a cell or organism having more than two paired (homologous) sets of chromosomes

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62
Q

What type of dominance allows us to determine genotype from phenotype?

A

Incomplete and co-dominance

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63
Q

True or False:

Once produced, a autotetraploid is an instant new species

A

True

(they are reproductively isolated from its diploid ancestor)

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64
Q

A Drosophila has the sex complement Y. What is it’s sex? Is it viable? Is it fertile?

A

Not viable

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65
Q

True or False:

The Hardy-Weinberg Principle describes a gene pool of a population that is evolving

A

False

Describes gene pool of a population that is no evolving

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66
Q

What would the recombinant frequency be if crossovers never occur between two gene loci?

A

0

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67
Q

What are the consequences of balanced translocations?

A
  • Breakpoints can disrupt important genes
  • Individuals heterozygous for a translocation have a variable risk of producing unbalanced gametes
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68
Q

Define

G-banding

A

a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is useful for identifying genetic diseases through the photographic representation of the entire chromosome complement. Also known as Giemsa banding

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69
Q

How do you calculate the degree of interference?

A

1 - coefficient of confidence (c)

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70
Q

Definition

a group of organisms of a species that interbreed and live in the same place at a same time

A

Population

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71
Q

Define

Phenotypic dimorphism

A

the existence of two different forms (as of color or size) of a species especially in the same population

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72
Q

Definition

a principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors

A

Hardy-Weinberg principle

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73
Q

Why are 3 point crosses more accurate than 2 point crosses?

A

3 point crosses are able to include double crossovers

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74
Q

Definition

an unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other.

A

Iso-chromosome

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75
Q

Define

Edwards syndrome

A

a genetic disorder caused by a third copy of all or part of chromosome 18

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76
Q

The simplest variant of a DNA sequence is called what?

A

Single nucleotide polymorphisms (SNPs)

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77
Q

What is it called when two genes are on a single pair of homologs and no exchange occurs? What is the F2 ratio?

A

Complete linkage 3:1

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78
Q

Definition

having the centromere situated so that one chromosome arm is somewhat shorter than the other

A

Submetacentric

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79
Q

True or False:

Unequal crossing over can occur between non-sister chromatids in both meiosis and mitosis

A

False

Unequal crossing over can occur between non-sister chromatids in meiosis but it only occurs between sister chromatids during mitosis

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80
Q

A RF of more than what requires a chi squared test to see if the genes are linked?

A

25

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81
Q

Define metacentric

A

having the centromere medially situated so that the two chromosomal arms are of roughly equal length

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82
Q

Define

Allodiploid

A

having two complete sets of chromosomes derived from two different species

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83
Q

Definition

a phenomenon in which sections of the genome are repeated and the number of repeats in the genome varies between individuals in the human population

A

Copy number variation

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84
Q

Define

Cytogenetics

A

a branch of genetics that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis

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85
Q

Define

Morphological

A

relating to the form or structure of things

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86
Q

If crossing over occurs during mitosis early in development, what will happen?

A

It will give rise to a patch of tissue different to the rest called a mitotic clone

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87
Q

True or False:

All genes on inactivated X chromosome are inactivated

A

False

~15% are not

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88
Q

Which of the following techniques allows the visualisation of initially smalle amounts o a particular stretch of DNA? a) Southern Blotting b) Cloning into bacteria c) PCR d) Combination of above

A

d) Combination of above

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89
Q

If the observed number of crossovers is more than expected what has occurred?

A

Negative interference

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90
Q

Define

Monosomy

A

the condition of having a diploid chromosome complement in which one chromosome lacks its homologous partner

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91
Q

Define

Maintenance

A

the final step in X inactivation where the inactivation is maintained by continued XIST expression in the Barr body in interphase

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92
Q

Where is gene B localised?

A

Chromosome 3

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93
Q

What are the problems with DNA fingerprinting?

A
  • Southern blots require large amounts of DNA (several micrograms)
  • The DNA must be intact (can’t reliably use degraded samples)
  • Can be hard to interpret - are similar bands really the same allele from the same locus?
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94
Q

What are the phenotypic characteristics of allopolyploids?

A

Resembles a blend of the parent species

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95
Q

What type of phase is this? Ab/aB

A

Repulsion phase

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96
Q

What is an inactivated X chromosome called?

A

Barr body

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97
Q

Definition

a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone

A

Balancing selection

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98
Q

Definition

an evolutionary process by which the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population

A

Frequency-dependent selection

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99
Q

A human recessive disorder albinism occurs in 1/10,000 births.

What is the expected frequency of carriers?

A
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100
Q

What is the gene that regulates X inactivation?

A

XIST

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101
Q

Definition

evolutionary change within a species or small group of organisms, especially over a short period.

A

Microevolution

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102
Q

Definition

an individual or strain whose chromosome complement consists of more than two complete copies of the genome of a single ancestral species

A

Autopolyploid

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103
Q

Definition

a multinucleate cell that contains genetically different nuclei

A

Heterokaryon

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104
Q

When there is a gain or loss of genetic material, what type of rearrangement is it?

A

Unbalanced

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105
Q

What is the maximum proportion of the genome that can be deleted without it being lethal?

A

2%

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106
Q

Definition

a sex-determining gene on the Y chromosome in mammals that determines maleness and is essential for development of the testes

A

SRY

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107
Q

What is somatic polyploidy?

A

Normal variation in euploidy in certain tissues

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108
Q

What are the phenotypic characteristics of autopolyploids?

A

Resembles parent species, larger and slower growing

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109
Q

What are duplications caused by?

A

Mostly caused by abnormal crossing over of chromosome mispair due to presence of repeated sequences in genome

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110
Q

What is the difference between DNA fingerprinting and DNA profiling?

A
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111
Q

Define

Chromosome painting

A

The use of fluorescent-tagged chromosome-specific dispersed repeat DNA sequences to visualize specific chromosomes or chromosome segments by in situ DNA hybridization and fluorescence microscopy

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112
Q

SRY was located through rare abnormal cases of XX males and XY females. What happens to the SRY in these cases?

A

SRY gene is now on the X in 46, XX males

SRY gene is not on the Y in 46, XY females

  • Arises by rare crossovers below the SRY gene at meiosis
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113
Q

How many chromosomes do humans have?

A

46

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114
Q

Define

Fluorescent in situ hybridisation (FISH)

A

a molecular cytogenetic technique that uses fluorescent probes that bind to only those parts of the chromosome with a high degree of sequence complementarity

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115
Q

Define restriction enzymes

A

an enzyme produced chiefly by certain bacteria, that has the property of cleaving DNA molecules at or near a specific sequence of bases

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116
Q

True or False:

Allodiploids are fertile

A

False

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117
Q

True or False:

Allopolyploid mammals are not usually viable

A

True

(there are exceptions i.e. mule)

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118
Q

Define

Pseudo-autosomal

A

regions on the X and Y chromosomes where crossing over occurs exhibiting autosomal, rather than sex-linked, pattern of inheritance

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119
Q

Define

Pericentric inversion

A

a reversal of the normal order of genes in a chromosome segment involving parts of a chromosome at both sides of the centromere

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120
Q

Define

Trivalent

A

a chromosome formed by three homologous chromosomes that lie close together or appear to join completely during meiosis

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121
Q

Definition

A region on the long (q) arm of chromosome 21 thought to be responsible for some, if not all, of the features of Down syndrome

A

Down syndrome critical region (DSCR)

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122
Q

Define

Dosage compensation

A

the process by which organisms equalize the expression of genes between members of different biological sexes

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123
Q

Define

Polymorphism

A

the presence of genetic variation within a population, upon which natural selection can operate

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124
Q

The distance between two loci that will generate 1% recombination between them is…

A

1 map unit

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125
Q

What are the defects caused by deletions the result of?

A

Haplo-insufficiency

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126
Q

Define

Dicentric chromosome

A

an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments

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127
Q

What do you need to consider if the map distance between the outer loci is less than the sum of the teo internal regions?

A

Double recombination evens

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128
Q

Definition

an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments

A

Dicentric chromosome

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129
Q

Definition

a product of reciprocal translocation that occurs at anaphase I that results in all gametes being unbalanced. The centromeres from the homologous chromosomes are separated

A

Adjacent I orientation

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130
Q

Define

Submetacentric

A

having the centromere situated so that one chromosome arm is somewhat shorter than the other

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131
Q

Define

Balancing selection

A

a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone

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132
Q

Define gel electrophoresis

A

a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores

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133
Q

Definition

A type of chromosome rearrangement involving the exchange of chromosome segments between two chromosomes that do not belong to the same pair of chromosomes

A

Reciprocal translocation

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134
Q

What is the maximum recombinant frequency between two loci?

A

50

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135
Q

Define southern blotting

A

a procedure for identifying specific sequences of DNA, in which fragments separated on a gel are transferred directly to a second medium on which assay by hybridization may be carried out

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136
Q

What circumstances can increase the effect of genetic drift?

A

Bottleneck

Founder effects

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137
Q

Definition

a condition characterised by the presence of an extra X chromosome in each cell of a female

A

Triple X syndrome

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138
Q

Is Adjacent I balanced or unbalanced?

A

Unbalanced

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139
Q

If a population size is not very large, what causes changes to genotype and allele frequency?

A

Genetic drift

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140
Q

Define

Double Y syndrome

A

a genetic condition in which a male has an extra Y chromosome. Symptoms are usually few. They may include being taller than average, acne, and an increased risk of learning problems

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141
Q

True or False:

Many small duplications have no phenotypic effect

A

True

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142
Q

Which part of the human sex chromosomes always has one crossover?

A

The paired pseudoautosomal region (1) at the end of the short arm

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143
Q

What are the different applications of DNA fingerprinting and profiling?

A

Clinical

Forensic

Legal

Conservation biology

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144
Q

What is this an image of?

A

Balanced reciprocal translocation

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145
Q

What percentage of an individual heterozygous for reciprocal translations gametes are unbalanced?

A

~50%

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146
Q

Define

Klinefelter’s syndrome

A

a genetic condition that results when a boy is born with an extra copy of the X chromosome

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147
Q

Define crossover event

A

the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction

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148
Q

Which three autosomal trisomies survive to term?

A

21 (Down syndrome)

13 (Patau syndrome)

18 (Edwards syndrome)

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149
Q

Define

Non-disjunction

A

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei

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150
Q

Definition

A chromosome pair with some homology but differing in size, shape, or staining properties. Homologous chromosome pair which are not morphologically identical (eg the sex chromosomes)

A

Heteromorphic chromosome

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151
Q

What type of dominance is seen for DNA markers?

A

Co-dominance

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152
Q

Define

Paracentric inversion

A

a reversal of the normal order of genes in a chromosome segment involving only the part of a chromosome at one side of the centromere

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153
Q

What are the three possible patterns that homologous chromosomes in a translocation cross can segregate into?

A

Alternate orientation

Adjacent I orientation

Adjacent II orientation

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154
Q

Definition

having the centromere terminally situated so that there is only one chromosomal arm

A

Telocentric

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155
Q

How many alleles do RFLP markers have?

A

Usually 2 (4 theoretically possible)

156
Q

What are the two types of balancing selection?

A

Heterozygote advantage

Frequency-dependent selection

157
Q

When much higher proportions of the parental gamete types occur than expected what is the suspected cause?

A

Linkage

158
Q

A Drosophila has the sex complement XY. What is it’s sex? Is it viable? Is it fertile?

A

Male

Viable

Fertile

159
Q

Define genetic map

A

A graphic representation of the arrangement of a gene or a DNA sequence on a chromosome. A genetic map is used to locate and identify the gene or group of genes that determines a particular inherited trait

160
Q

Define

Telocentric

A

having the centromere terminally situated so that there is only one chromosomal arm

161
Q

What are the possible gametes for a paracentric inversion with no crossovers within the inverted region?

A
162
Q

True or False:

Autotetraploids are fertile

A

True

163
Q

What would the recombinant frequency be if a crossover always occured between two gene loci?

A

50

164
Q

Why can DNA profiling be used when the DNA sample is partially degraded?

A

The PCR will only amplify the intact DNA, degraded DNA will simply not amplify

165
Q

Definition

an alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents or in the fertilized egg itself

A

De novo mutation

166
Q

What type of dominance does RFLP alleles display?

A

Co-dominance

167
Q

How do you describe the position of a gene on a chromosome using the correct nomenclature?

A
  1. Chromosome number
  2. Chromosome arm (p/q)
  3. Region of arm sub-divided by landmark G-bands
  4. Position within region
168
Q

Define microsatellite

A

a tract of repetitive DNA in which certain DNA motifs (ranging in length from 1–6 or more base pairs) are repeated, typically 5–50 times

169
Q

Small duplications retained in the genome lead to what?

A

Copy number variation

170
Q

What is this an example of?

A

Reciprocal translocation

171
Q

How many Barr bodies does X have?

A

0

172
Q

Define repulsion phase

A

A linkage between dominant alleles of one or more genes and the recessive alleles of another (several genes) in such a case one parent involved in cross contributes the domi­nant allele of one gene while second parents provides the domi­nant allele of other genes

173
Q

Why is the sickle cell anaemia allele retained in some African populations, despite the severity of the disease of the sickle cell homozygote?

A

Heterozygote advantage - individuals heterozygous for this allele are resistant to malaria

174
Q

Define

Acentric

A

describes a chromosome without a centromere

175
Q

Define

Reciprocal translocation

A

A type of chromosome rearrangement involving the exchange of chromosome segments between two chromosomes that do not belong to the same pair of chromosomes

176
Q

How is it decided which X will be inactivated?

A

Random

177
Q

Definition

The use of fluorescent-tagged chromosome-specific dispersed repeat DNA sequences to visualize specific chromosomes or chromosome segments by in situ DNA hybridization and fluorescence microscopy

A

Chromosome painting

178
Q

True or False:

In interspecies hybrids, chromosomes of one or the other parent are progressively and random lost

A

True

179
Q

What are two reasons why monosomy of autosomes is inviable?

A
  1. Recessive disease alleles
  2. Haploinsufficiency (50% not enough)
180
Q

Define map unit

A

the distance between chromosome positions (also termed loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. Also known as a centiMorga

181
Q

What is the evolutionary advantage of inversions?D

A
182
Q

True or False:

Monosomy is more abnormal than trisomy

A

True

183
Q

Definition

the stock of different genes in an interbreeding population.

A

Gene pool

184
Q

Definition

an aberrant chromosome whose ends have fused together to form a ring

A

Ring chromosome

185
Q

Definition

the production or development of an ovum

A

Oogenesis

186
Q

Definition

a reversal of the normal order of genes in a chromosome segment involving parts of a chromosome at both sides of the centromere

A

Pericentric inversion

187
Q

Definition

the presence of genetic variation within a population, upon which natural selection can operate

A

Polymorphism

188
Q

If the allele frequency of p is 0.8 what is the allele frequency of q?

A

0.2

189
Q

What DNA marker does DNA fingerprinting target?

A

Minisatellite

190
Q

Definition

the state of a cell or organism having more than two paired (homologous) sets of chromosomes

A

Polyploidy

191
Q

How do we detect SNPs?

A
  1. Detect RFLP by restriction enzyme digestion of genomic DNA and Southern Blotting 2. Detect RFLP using PCR from genomic DNA follwed by restriction enzyme digestion
192
Q

Define

Population genetics

A

a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology

193
Q

Definition

describes a chromosome without a centromere

A

Acentric

194
Q

The genotype for closely liked genes on a single chromosome or gamete is called what?

A

Haplotype

195
Q

What are the benefits of genetic mapping?

A
  1. Tells you whether a disorder is caused by one gene or by different genes
  2. Genes whose DNA sequence is not yet known can be cloned from their map position
  3. Nearby markers can be used as a tag of a desired gene in plant and animal breeding
  4. Closely liked DNA markers are useful in genetic counseling
196
Q

Define DNA fingerprinting

A

a technique used especially for identification (as for forensic purposes) by extracting and identifying the base-pair pattern of an individual’s DNA

197
Q

Define

Adjacent II orientation

A

a product of reciprocal translocation that occurs at anaphase I that results in all gametes being unbalanced. The centromeres from homologous chromosomes end up in the same gametes making this vary rare

198
Q

Definition

the process by which organisms equalize the expression of genes between members of different biological sexes

A

Dosage compensation

199
Q

Define founder effects

A

the reduced genetic diversity which results when a population is descended from a small number of colonizing ancestors

200
Q

How do you calculate the coefficient of confidence (C)?

A

Observed double crossovers / Expected double crossovers

201
Q

Define

Aneuploidy

A

the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46

202
Q

In mitosis, homologous chromosomes do/don’t pair to form bivalents

A

Don’t

203
Q

Which of the common human sex chromosome aneuploids are fertile?

A

Triple X

Double Y

204
Q

Define probe

A

A single-stranded DNA or RNA fragment used in genetic engineering to search for a particular gene or other DNA sequence. The probe has a base sequence complementary to the target sequence and will thus attach to it by base pairing

205
Q

How many pairs of chromosomes do humans have?

A

23

206
Q

An inversion with the centromere inside the inverted region is called what?

A

Pericentric

207
Q

What effect does the size of pericentric inversions have on fertility?

A

The larger the inversion, the more likely crossovers will occur, increasing the chance of unbalanced gametes, further reducing fertility

208
Q

What does an inversion or translocation arising and spreading through a population promote? How?

A

Speciation

209
Q

Definition

a product of reciprocal translocation that occurs at anaphase I that results in half the gametes being normal and the other half being unbalanced

A

Alternative orientation

210
Q

True or False:

The ratio of males to females is 1:1

A

False

Female slightly favoured

211
Q

Define negative interference

A

the phenomenon that the occurrence of a crossover increases the probability of another crossover in its vicinity

212
Q

Define multiplex PCR

A

the use of polymerase chain reaction to amplify several different DNA sequences simultaneously (as if performing many separate PCR reactions all together in one reaction)

213
Q

Define

Turner’s syndrome

A

a genetic defect in which affected women have only one X chromosome, causing developmental abnormalities and infertility

214
Q

Abnormal chromosomes only survive mitosis/meiosis is it still has ___ centromere and ____ telomeres

A

1 centromere and 2 telomeres

215
Q

How do autotriploids form?

A

Arises if a diploid gamete (2n) joins with a haploid gamete (1n)

216
Q

Robertsonian translocations occur only in what type of chromsome?

A

Acrocentric

217
Q

What are the potential consequences of a balanced inversion?

A
  • Breakpoints can disrupt important genes
  • Individuals heterozygous for an inversion have a variable risk (depending on inversion size) or producing unbalanced gametes
218
Q

Definition

having two complete sets of chromosomes derived from two different species

A

Allodiploid

219
Q

Fusion of which chromosomes via Robertsonian translocation often results in Down syndrome?

A

14 and 21

220
Q

Definition

the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46

A

Aneuploidy

221
Q

What are the five assumptions of the HW principle?

A
  1. The population is very large
  2. There is no gene flow
  3. There is no natural selection
  4. There is no mutation
  5. There is random mating
222
Q

What gametes are produced in nondisjunction I in females?

A
223
Q

Define allele specific oligonucleotide hybridisation

A

a procedure for detection of alleles of known composition, by measuring hybridization of a labeled DNA sample with oligonucleotide probes of known sequence, differing from each other by a single nucleotide, under conditions stringent enough that only perfectly matched sequences hybridize

224
Q

Define DNA profiling

A

the process where a specific DNA pattern, called a profile, is obtained from a person or sample of bodily tissue

225
Q

Define

Fragile X syndrome

A

an inherited condition characterized by an X chromosome that is abnormally susceptible to damage, especially by folic acid deficiency. Affected individuals tend to have limited intellectual functions

226
Q

Define

Directional selection

A

a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype

227
Q

When nondisjunction occurs in meiosis II what happens?

A

Failure of a pair of sister chromatids to separate - two chromatids got to one pole and note to other

228
Q

Define

De novo mutation

A

an alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents or in the fertilized egg itself

229
Q

What are the resulting gametes when nondisjunction occurs at meiosis II?

A
230
Q

True or False:

Polyploid occurs in mammals

A

False

It never occurs in mammals

231
Q

What are the male and female sex chromosome system in birds?

A

F: ZW

M: ZZ

232
Q

Definition

an inherited condition characterized by an X chromosome that is abnormally susceptible to damage, especially by folic acid deficiency. Affected individuals tend to have limited intellectual functions

A

Fragile X syndrome

233
Q

Definition

composed of four homologous chromosomes synapsed in meiotic prophase

A

Quadrivalent

234
Q

What causes female mammals to be natural mosaics?

A

X inactivation

235
Q

Why are normal gametes produced by 47, XXX and 47, XYY?

A
  • During early development of the germ line the normal karyotype is restored, so oocytes are 46, XX and spermatogonia are 46, XY
  • Achieved as one sex chromosome is lost (e.g. by nondisjunction or lagging) during early mitosis. Only cells in which this has occurred can lead to the germ line
236
Q

What happens once a gene duplicates?

A
237
Q

When nondisjunction occurs in meiosis I what happens?

A

Failure of separation of a pair of homologous chromosomes - two homologues go to one pole and none to other

238
Q

Define

Triple X syndrome

A

a condition characterised by the presence of an extra X chromosome in each cell of a female

239
Q

How do homologous chromosomes behave at meiosis when they are heterozygous for a Robertsonian translocation?

A
240
Q

How many Barr bodies does XX have?

A

1

241
Q

Definition

a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype

A

Directional selection

242
Q

Definition

an individual or strain whose chromosome complement consists of four copies of a single genome due to doubling of an ancestral chromosome complement

A

Autotetraploid

243
Q

Define intragenic recombination

A

recombination occurring within a gene

244
Q

Which of the following chromosome types segregates normally during cell division?

a) dicentric
b) acentric
c) ring
d) iso

A

d) iso

245
Q

Define variable number of tandem repeats (VNTR)

A

another name for a minisatellite

246
Q

Definition

a genetic condition that results when a boy is born with an extra copy of the X chromosome

A

Klinefelter’s syndrome

247
Q

Define genetic chimera

A

a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction

248
Q

What does unequal crossing over cause?

A

Both duplications and deletions

249
Q

Define

Stabilising selection

A

a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value

250
Q

Definition

having or existing in only one form

A

Monomorphic

251
Q

Define

Patau syndrome

A

a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13

252
Q

Definition

a stain that labels the phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of adenine-thymine bonding. Giemsa stain is used in Giemsa banding, commonly called G-banding, to stain chromosomes and often used to create a karyogram

A

Giemsa stain

253
Q

Human genes can be mapped using somatic cell hybrids as long as what requirements are met?

A
  1. Human gene product identifiable in cell culture
  2. Products of human and other species genes can be distinguished
254
Q

Define

Reproductive isolation

A

the situation where different species may live in the same area, but properties of individuals prevent them from interbreeding

255
Q

What are the three possible ways chromosomes in a trivalent can segregate?

A

Normal, balanced or unbalanced

256
Q

How is DNA profiling performed?

A

PCR is used to detect and amplify DNA at one locus

257
Q

What effects does the size of a paracentric inversion have on fertility?

A

The larger the inversion, the more likely crossovers will occur leading to more abnormal gametes and less fertility

258
Q

What can high resolution genetic maps tell you?

A

Whether the markers are linked as well as generating a genetic map

259
Q

If the chromosome number is double during meiosis to form a allotetraploid, what can occur?

A

All the chromosomes can form bivalents at meiosis and balanced diploid gametes will be produced making it fertile

260
Q

What are the advantages of DNA profiling?

A
  • PCR is extremely sensitive, requires very little starting material
  • Can genotype partially degraded DNA samples
261
Q

What is this showing?

A

Unequal crossing over

262
Q

Definition

a genetic defect in which affected women have only one X chromosome, causing developmental abnormalities and infertility

A

Turner’s syndrome

263
Q

What are the male and female sex chromosome system in mammals?

A

F: XX

M: XY

264
Q

Define minisatellite

A

a tract of repetitive DNA in which certain DNA motifs (ranging in length from 10–60 base pairs) are typically repeated 5-50 times

265
Q

What are the male and female sex chromosome system in many turtles?

A

F: high temp

M: low temp

266
Q

Definition

a product of reciprocal translocation that occurs at anaphase I that results in all gametes being unbalanced. The centromeres from homologous chromosomes end up in the same gametes making this vary rare

A

Adjacent II orientation

267
Q

True or False:

Autotriploids are fertile

A

False

268
Q

Define centiMorgan

A

a map unit used to express the distance between two gene loci on a chromosome. A spacing of one centimorgan indicates a one per cent chance that two genes will be separated by crossing over

269
Q

True or False:

Somatic polyploidy occurs in humans

A

True

270
Q

True or False:

The silenced X chromosome reactivates in oogenesis

A
271
Q

Definition

an individual or strain whose chromosomes are composed of more than two genomes each of which has been derived more or less complete but possibly modified from one of two or more species

A

Allopolyploid

272
Q

Define PCR

A

a technique in molecular genetics that permits the analysis of any short sequence of DNA (or RNA) even in samples containing only minute quantities of DNA or RNA

273
Q

Define bivalent

A

a pair of homologous chromosomes

274
Q

Define

Monomorphic

A

having or existing in only one form

275
Q

True or False:

Monosomies never survive

A

True

276
Q

Define haplotype

A

a group of alleles in an organism that are inherited together from a single parent

277
Q

What are the possible gametes of a pericentric inversion with a crossover within the inverted region?

A
278
Q

What are the four common human sex chromosome aneuploids?

A

Triple X

Turner

Double Y

Klinefelter

279
Q

Define

Iso-chromosome

A

an unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other.

280
Q

Drosophila also has XX females and XY males. Is the mechanism the same as in mammals?

A

No

2 or more X = female

Only 1 X = male

Y needed for functional sperm

281
Q

Genes A; B; C; D are found on which chromosome?

A

A: Chromosome 5

B: Chromosome 3

C: Chromosome 8

D: Chromosome 1

282
Q

Define

Heteromorphic chromosome

A

A chromosome pair with some homology but differing in size, shape, or staining properties. Homologous chromosome pair which are not morphologically identical (eg the sex chromosomes)

283
Q

True or False:

In plants, if two 2n gametes join the 4n zygote will be viable but not fertile

A

False

It will be both viable and fertile

284
Q

How are micro deletion syndromes detected?

A

High-resolution karyotyping or FISH

285
Q

What is this an example of?

A

Inversion

286
Q

Define

Allozymes

A

variant forms of an enzyme which differs structurally but not functionally from other versions coded for by different alleles at the same locus

287
Q

Label these chromosomes based on centromere position

A
288
Q

Define genomic DNA

A

chromosomal DNA

289
Q

Define

Inversion loop

A

the conformation of pairing up of homologous chromosomes in meiosis that are heterozygous for inversions

290
Q

How many Barr bodies does XY have?

A

0

291
Q

Define coefficient of coincidence

A

a measure of interference in the formation of chromosomal crossovers during meiosis

292
Q

True or False:

Allopolyploids arise from inter-species hybrids

A
293
Q

What are the two types of inversions?

A
294
Q

Fill in the gaps with either SNPs or Satellites

A
295
Q

Definition

the inactive X chromosome in female somatic cells

A

Barr body

296
Q

Define

Down syndrome

A

a congenital disorder arising from a chromosome defect, causing intellectual impairment and physical abnormalities including short stature and a broad facial profile. It arises from a defect involving chromosome 21, usually an extra copy (trisomy-21)

297
Q

Definition

the situation where different species may live in the same area, but properties of individuals prevent them from interbreeding

A

Reproductive isolation

298
Q

Why do trisomy 13, 18 and 21 have milder phenotypes than other autosomal trisomies?

A

They are smaller chromosomes with fewer essential genes

299
Q

Define

Uniparental disomy

A

the situation in which 2 copies of a chromosome come from the same parent, instead of 1 copy coming from the mother, and 1 copy coming from the father

300
Q

Which of the common human sex chromosome aneuploids are infertile?

A

Turner

Klinefelter

301
Q

True or False:

Autosomal aneuploid rates are not affected by maternal age

A

False

Autosomal aneuploid are more frequent among offspring of older mothers

302
Q

An inversion with the centromere outside the inverted region is called what?

A

Paracentric

303
Q

Females have twice the amount of genes on their X chromosome than males. How is this dosage imbalance corrected?

A

Dosage compensation

304
Q

Definition

a genetic disorder caused by a third copy of all or part of chromosome 18

A

Edwards syndrome

305
Q

What gametes are produced in nondisjunction I in males?

A
306
Q

What is an example of a method to detect SNPs that does not cause restriction site changes?

A

Allele specific oligonucleotide (ASO) hybridisation

307
Q

During a Robertsonian translocation, which arm of the chromosome is lost?

A

P arm

308
Q

True or False:

Centromeres are basically never completely centred so one arm will always be longer than the other

A

True

309
Q

What are the categories fo chromosomal rearrangements?

A

Deletion

Duplication

Inversion

Translocation

310
Q

Define restriction fragment length polymorphism (RFLP)

A

any variation in DNA between individuals revealed by restriction enzymes that cut DNA into fragments of different lengths in consequence of such variations

311
Q

Define

SRY

A

a sex-determining gene on the Y chromosome in mammals that determines maleness and is essential for development of the testes

312
Q

What is the method for chromosome painting?

A
  • Make a probe that contains many sequences from an individual chromosome (isolate the chromosome cytologically, or obtain DNA from library of clones from that chromosome)
  • Label probe chemically with fluorescent dye
  • Hybridise probe to chromosome spreads in situ
  • Results in only one chromosome type fluorescing (at many different sites along its length)
313
Q

True or False:

FISH can be used to detect inversions

A

True

314
Q

Define

Down syndrome critical region (DSCR)

A

A region on the long (q) arm of chromosome 21 thought to be responsible for some, if not all, of the features of Down syndrome

315
Q

Define

Allotetraploid

A

a hybrid that has a chromosome set 4 times that of a haploid organism. They are created as a result of both chromosome sets of each parents being present in gametes

316
Q

True or False:

Aneuploidy for sex chromosomes is more severe than for autosomes

A

False

Aneuploidy for autosomes is more severe than for sex chromosomes

317
Q

On which population does genetic drift have a larger effect: 20 or 2000?

A

20

318
Q

Define twin spots

A

two genetically different clones of neighboring cells in a background of normal cells

319
Q

True or False: There is no recombination in Drosophila females

A

False There is none in males

320
Q

What are the three steps of X inactivation?

A

Initiation

Spreading

Maintenance

321
Q

What gametes are produced in nondisjunction II in females?

A
322
Q

True or False:

All mammals share the same mechanism of sex determination

A
323
Q

How does the mutation in Fragile X syndrome affect the FMR1 gene?

A

The full repeat expansion reduced the expression of the gene

324
Q

What are the resulting gametes when nondisjunction occurs at meiosis I?

A
325
Q

Definition

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei

A

Non-disjunction

326
Q

What is an example of a morphological polymorphism?

A

Labrador coat colour

327
Q

Define single nucleotide polymorphism (SNPs)

A

a variation at a single position in a DNA sequence among individuals

328
Q

Define

Autopolyploid

A

an individual or strain whose chromosome complement consists of more than two complete copies of the genome of a single ancestral species

329
Q

Define

Genetic drift

A

variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce

330
Q

What is the difference between a microsatellite and a minosatellite?

A

The length: micro = 2-10bp mini = 10-100bp

331
Q

Can HW principle still be used to calculate the allele frequency of complete dominance traits?

A

Yes

332
Q

Define

Frequency-dependent selection

A

an evolutionary process by which the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population

333
Q

Definition

variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce

A

Genetic drift

334
Q

Define chiasmata

A

a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands

335
Q

Definition

relating to the form or structure of things

A

Morphological

336
Q

What is the term used to describe the transfer of genetic material between non-homologous chromosomes?

A

Translocation

337
Q

Definition

the most common form of chromosomal rearrangement where the participating chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere

A

Robertsonian translocation

338
Q

Define

Dicentric chromosome

A

an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments

339
Q

True or False:

Ring chromosomes are very stable and are often retained

A

False

They are very unstable and are often lost during meiosis

340
Q

Why are dicentric chromosomes lost during meiosis?

A

They form a dicentric bridge during meiosis, when chromosomes separate it will randomly break, resulting in variable deletion

341
Q

Definition

the situation in which 2 copies of a chromosome come from the same parent, instead of 1 copy coming from the mother, and 1 copy coming from the father

A

Uniparental disomy

342
Q

Define

Autotetraploid

A

an individual or strain whose chromosome complement consists of four copies of a single genome due to doubling of an ancestral chromosome complement

343
Q

Define

Adjacent I orientation

A

a product of reciprocal translocation that occurs at anaphase I that results in all gametes being unbalanced. The centromeres from the homologous chromosomes are separated

344
Q

What type or phase is this? AB/ab

A

Coupling phase

345
Q

Definition

a hybrid that has a chromosome set 4 times that of a haploid organism. They are created as a result of both chromosome sets of each parents being present in gametes

A

Allotetraploid

346
Q

Definition

an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments

A

Dicentric chromosome

347
Q

How does autotetraploidy occur?

A

Arises due to an accident during mitosis:

(chromosomes replicate but cell division does not occur)

348
Q

Define

Allopolyploid

A

an individual or strain whose chromosomes are composed of more than two genomes each of which has been derived more or less complete but possibly modified from one of two or more species

349
Q

Define

Alternative orientation

A

a product of reciprocal translocation that occurs at anaphase I that results in half the gametes being normal and the other half being unbalanced

350
Q

Define

Ring chromosome

A

an aberrant chromosome whose ends have fused together to form a ring

351
Q

What is the expected genotype frequency of a population in HW equilibrium?

A

p2 + 2pq + q2 = 1

352
Q

Definition

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities

A

Trisomy

353
Q

How is DNA fingerprinting performed?

A
  • Digest genomic DNA with a restriction enzyme and perform a Southen blot
  • Use a probe complementary to the repeat to detect ALL the repeat loci at once

This will give you a specific ‘fingerprint’ of bands

354
Q

Define

Gene pool

A

the stock of different genes in an interbreeding population.

355
Q

Define

Bottle neck

A

an event that drastically reduces the size of a population producing a decrease in the gene pool of the population because many alleles, or gene variants, that were present in the original population are lost

356
Q

How do the homologous chromosomes pair when a heterozygous reciprocal translocation has occurred?

A
357
Q

What are some examples of causes of directional selection?

A

Selective predation, pesticide resistance in insects etc.

358
Q

How was it determined that the presence of Y determines maleness?

A

Abnormal human karyotypes

Female: X, XX, XXX

Male: XY, XYY, XXY

359
Q

Define

Heterokaryon

A

a multinucleate cell that contains genetically different nuclei

360
Q

How many chromosomes would be found in somatic cells of an allotetraploid plant if its parent species had diploid number 4 and 6 respectively?

A

5

361
Q

Definition

a molecular cytogenetic technique that uses fluorescent probes that bind to only those parts of the chromosome with a high degree of sequence complementarity

A

Fluorescent in situ hybridisation (FISH)

362
Q

How many Barr bodies does XXXY have?

A

2

363
Q

Why are most interspecies hybrids that survive sterile?

A

Either meiosis does not occur, or the two sets of chromosomes do not pair (all univalents, no balanced gametes)

364
Q

Definition

the second step in X inactivation where the XIST RNA is not translated but spreads out and coats the inactivate X, ensuring most genes are inactivated

A

Spreading

365
Q

Define autonomous

A

having the freedom to act independently

366
Q

What are the different types of natural selection?

A
  1. Directional selection
  2. Stabilising selection
  3. Balancing selection
  • Heterozygote advantage
  • Frequency-dependent selection
367
Q

What are the disadvantages of DNA profiling?

A
  • Contaminating DNA can be easily amplified
  • Multiplex PCR must be carefully optimised so that PCR are one locus does not interfere with another
368
Q

Define

Quadrivalent

A

composed of four homologous chromosomes synapsed in meiotic prophase

369
Q

How do you describe human karyotypes using the appropriate nomenclature?

A
  1. Number of chromosomes per cell
  2. Complement of sex chromosomes
  3. Any abnormal chromosomes
    e. g. 47, XY, +21
370
Q

What type of DNA marker does DNA profiling target?

A

Microsatellite

371
Q

True or False:

Nondisjunction can occur during mitosis

A

True

372
Q

How does false inclusion occur in DNA profiling?

A
  • Relatives are likely to share alleles
  • Some alleles more frequent in specific populations (Founder effect)
  • Some markers show racial differences in allele frequency
373
Q

If the observed number of crossovers is less than expected what has occurred?

A

Positive interference

374
Q

When one chromosome arm is lost and the remaining arm is then duplicated, what is the result?

A

Iso chromosome

375
Q

Why are acentric chromosomes lost during meiosis?

A

They cannot attach to the spindle

376
Q

What are the causes of reciprocal translocations?

A
  • Chromosome breaks
    • Broken ends lack telomeres and are reactive, DNA repair enzymes may re-join incorrectly
  • Abnormal crossing over between non-homologous chromosomes
377
Q

The probability of mutation to a different allele per gene per generation is referred to as what?

A

Mutation rate (µ)

378
Q

True or False

Sex chromosome aneuploidy is more common than autosome aneuploidy

A

True

379
Q

What is this an example of?

A

Deletion

380
Q

A Drosophila has the sex complement XX. What is it’s sex? Is it viable? Is it fertile?

A

Female

Viable

Fertile

381
Q

If an individual is heterozygous for an inversion, how do homologous chromosomes pair?

A

Inversion loop

382
Q

Define

Microevolution

A

evolutionary change within a species or small group of organisms, especially over a short period.

383
Q

Definition

a reversal of the normal order of genes in a chromosome segment involving only the part of a chromosome at one side of the centromere

A

Paracentric inversion

384
Q

Define

Spreading

A

the second step in X inactivation where the XIST RNA is not translated but spreads out and coats the inactivate X, ensuring most genes are inactivated

385
Q

Define

Initiation

A

the first step in X inactivation where the X inactivation centre (Xic) of one of the X chromosome is initiated by the expression of the gene XIST

BMS2042 (9 decks)

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