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Genetics & Molecular Biology > Mendelian Genetics > Flashcards

Mendelian Genetics Flashcards

(60 cards)

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1
Q

Define Diploid

A

number of chromosomes in the somatic (body) cells
- in humans the diploid number is 46

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2
Q

Define Haploid

A

A single set chromosomes present in the egg & sperm of animals, egg & pollen of plants and in stable/transient life cycle forms of other organisms

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3
Q

Define Chromosome

A

self-replicating structures of cells that carry their nucleotide sequences in an literal array of genes

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4
Q

Define Karyotype

A

the entire chromosomes complement of an individual or cell as seen during the mitotic metaphase

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5
Q

Define Allele

A

1 of the different forms of a gene or DNA sequence that can exist at a single locus

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6
Q

Define Genotype

A

the actual alleles present in an indvidual

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7
Q

Define Phenotype

A

Observable characteristics of an organism

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8
Q

Define Trait

A

Any detachable phenotypic variation of particular inherited character

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9
Q

Define Gene

A

the fundamental physical and functional unit of heredity , which carrier info from 1 generation to the next, a segment of DNA, composed of a transcribed region and a regulatory sequence that makes transcription possible

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10
Q

Define Zygote

A

the single cell with 46 chromosomes resulting from the fertilisation of an egg by a sperm

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11
Q

Define Homozygous

A

Having 2 of the same alleles at a given locus on a pair of homologous chromosomes

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12
Q

Define Heterozygous

A

having 2 different alleles at a given locus on a pair of homologous chromosomes

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13
Q

What are the desirable characteristics of plants ?

A
  • can be grown in large quantities
  • produce a large number of offspring - seeds
  • relatively short generation times
  • many have male & female reproductive
  • easy to control which individuals mate
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14
Q

Describe Mendel’s Experimental Methods

A
  • hand-pollinated flowers using painbrush
  • he could snip the stamens to prevent self-pollination
  • covered each flower with a cloth bag
  • he traced traits through several generations
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15
Q

What are the 8 pea plant traits ?

A

seed shape
seed colour
pod shape
pod colour
seed coat colour
flower position
plant height
flower colour

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16
Q

Describe Mendel’s well-ordered experimental plan

A
  • used characters that were well-defined alternative traits –> purple/ white flowers - spherical/wrinkled peas
  • were true-breeding –> only form present for many generations - parent generations
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17
Q

What are progeny from the cross of P parents called ?

A

the first filial generation (F1)

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18
Q

Define Monohybrid cross

A

cross involving a single trait –> flower colour

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19
Q

Define Dihybrid cross

A

cross involving 2 traits –> flower colour & plant height

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20
Q

What is Mendel’s 1st Law of Inheritance ?

A
  • Law of unit characters
  • Every trait is controlled by at least 1 pair of genes
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21
Q

Describe the Law of Assortment

A

alleles of different genes assort into gametes independently of each other

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22
Q

Describe the Law of Domimance

A
  • one of the genes in the pair may be dominant over the other which is recessive
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23
Q

Describe the Law of Segregation

A
  • the genes pair separate when gametes are formed
  • only 1 of each gene pairs is represented in each of the gametes
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24
Q

Describe the F1 monohybrid cross results

A
  • heterozygous X heterozygous
  • 25% homozygous dominant RR
  • 50% Heterozygous Rr
  • 25% Homozygous Recessive rr
  • offspring is called F2 generation
  • genotypic ratio = 1:2:1
  • phenotypic ratio = 3:1
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25
Define Codominance
2 alleles are expressed in heterozygous individuals - example = blood type
26
What are the 2 kinds of probability ?
- empirical probability - theoretical probability
27
Define Empirical Probability
- its calculated by counting the number of times that event occurs and dividing it by the total number of times than event could have occurred
28
Define Theoretical Probability
- its calculated & reflects the number of times an even is expected to occur relative to the number of time it could possibly occur
29
Describe Pedigrees
- family trees - show phenotype segregation in several generations of related individuals
30
Define Single Gene Disorders
- changes/mutations in the DNA sequence of one gene
31
What are some subtypes of single gene disorders ?
- autosomal dominant - autosomal recessive - X-linked dominant - X-linked recessive - Y-linked
32
Describe Autosomal Dominance Inheritance
- Aa & AA are affected - all affected individual should have an affected parent - both sexes should be equally affected - Example = Huntington's Disease
33
Describe Huntington's Disease
- caused by a triple repeat expansion in the Huntingtin gene - occurence = 1/100,000 - symptoms = personality change, progressive chorea, dystonia & dementia
34
Describe Autosomal Recessive Inheritance
- only aa are affected, Aa are carriers - usually no previous family history - inbreeding increases the chance of observing an autosomal recessive condition - example = cystic fibrosis
35
Describe Cystic Fibrosis
- caused by a mutation in the CFTR gene - 1/25 people are carriers - Symptoms = chronic obstruction of the airway, shortness of breath, malnutrition & infertility
36
Define Wild Type Alleles
most common allele in population >99%
37
Define Mutant allele
may produce a phenotype different from that of the wild-type allele
38
Describe Incomplete Dominance
- when 2 traits 'meet in the middle' instead of showing a definite dominant/recessive relationship - Red X white snapdragons = 1:2:1 ratio of Red:pink:white flowers
39
Define Pleotropic alleles
single alleles with more than 1 distinguishable phenotypic effect --> colouration pattern & crossed eyes in siamese cats = caused by the same allele
40
Define Epistasis
- alleles of 1 gene cover up or alter expression of alleles of another gene - example = several genes determine coat colour in Labrador retriever
41
Describe how coat colour is determined in dogs
- a single dominant allele at the first locus influences the expression or allele at a second gene locus - Black Labs = BBEE, BBEem BbEe - Chocolate Labs = bbEE, bbEe - Yellow Labs with Dark skin = BBee or Bbee - Yellow labs with pale skin = bbee
42
In what scenarios does epistasis occur ?
- whenever 2 or more loci interact to create new phenotypes - whenever an allele at 1 locus masks the effects - whenever an allele at one locus modifies the effect of ales at 1 or more other loci
43
Describe how temperature effects evening primrose
- mutations affected by temp are conditional or temperature-sensitive mutations - evening primrose produces red flowers at 23 degrees and white flowers at 18
44
Describe how temperature effects Himalayan Rabbit
- has black fur on its extremities due an ancestral trait - temperature sensitive tyrosinase genes which controls fur pigmentation - natural selection has favoured a gene that allows for a darker pigmentation which activates in low temperatures - chaining the individual rabbits phenotype to fit the climate - black fur absorbs light & solar heat, keeping that part of the rabbit which has dark fur warmer
45
Define penetrance
proportion of individuals in a group with a given genotype that actually show the expected phenotype
46
Define Expressivity
Degree of expression of a given trait or combination of traits that is associated with a gene - condition may have severe or mild symptoms
47
Define Monoecious
- example = corn & peas - every diploid adult has both male & female reproductive structures
48
Define Dioecious
- example = other plant & most animals - some individual produce only male gametes, other produce only femlae gametes
49
What are examples Sex Chromosomal Disorders ?
- Turner's syndrome - XO, monosomy X - Triple-X syndrome - XXX - Jacob's Syndrome - XYY
50
Describe Sex Determination
- some XY individuals lack a small portion of Y chromosomes are phenotypically female - some XX individuals with a small piece of the Y chromosome are male - fragment contains the maleness-determining gene - SRY = Sex-determining Region on the Y chromosome - SRY codes for a functional protein - protein present = testes develop
51
Describe X chromosome inactivation
- Anhidrotic ectodermal dysplasia - EDA gene which are inherited in an X-linked recessive pattern - Małe hemizygotes = no teeth, sparse hair & no sweat glands - female hemizygotes = random patterns of tissue, with/without sweat glands
52
Describe Sex Linked Inheritance in relation to Pedigrees
- phenotype appears much more often in males than female - male with mutation can only pass it to his daughters - daughters who receive 1 mutant X are heterozygous carriers
53
Describe X-Linked Dominant Inheritance
- females and males are affected - no cases of male to male transmission - examples = Focal Dermal Hypoplasia & Familial Hypophosphatemic rickets
54
Describe X-Linked Recessive Inheritance
- affected males have normal sons & carrier daughters - affected females will have 50% chance that their child inherits the disorder (sons) or is a carrier (daughters) - examples = Colour blindness & Haemophilia
55
Describes Y-Linked Inheritance
- only males affected - no cases of male --> female transmission - usually results in infertility - Y chromosome is relatively small and contains few genes so there are relatively few y-linked disorders
56
Describe Maternal Inheritance
- a mother with mitochondrial DNA gene mutation will pass abnormal gene to all her children - children will all be affected with varying degrees of severity
57
Define Homoplasmic cells
homoplasmic cells = cells which only contain normal mtDNA
58
Define Heteroplasmic cells
- people with a maternally inherited disease and their maternal relatives usually have heterplasmic cells --> some of the mtDNA is normal and some aren't - containing mutations
59
Describe Mosaicism
- somatic mosaicism = occurrence of 2 genetically distinct populations of cells within an individual - derived from a post zygotic mutation - may only affects a portion of the body & isn't transmitted to the progeny
60
Describe Genomic Imprinting
- for imprinted genes only 1 working copy is inherited - as opposed to 2 - 1 from each parent - depending on the gene one gene copy is epigenetically silenced - silencing usually happens through the addition of methyl groups during gamete formation

Genetics & Molecular Biology (13 decks)

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