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Biology: Genetics > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

Modifications occur at the level of…

A

the chromosome

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2
Q

Phenotypic variations result from changes of

A

individual genes

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3
Q

What are some chromosome mutations or aberrations that could occur?

A

-Total number of chromosomes vary
-Deletions of genes or segments
-Duplications of genes or segments
-Rearrangements of genetic material within or among chromosome

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4
Q

Aneuploidy

A

-Variations in chromosome number
-Organism gains or loses one or more chromosomes (not the entire set)

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5
Q

Aberration

A

The chromosomal number is altered

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6
Q

Mutation

A

an alteration in the nucleic acid sequence of the genome of an organism, virus, or extra chromosomal DNA.

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7
Q

Monosomy

A

Loss of single chromosome in diploid genome

2n - 1

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8
Q

Trisomy

A

Gain of a single chromosome

2n + 1

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9
Q

Euploidy

A

Complete haploid sets of chromsomes are present

MULTIPLES OF N

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10
Q

Polyploidy

A

More than two sets of chromosomes are present

3n, 4n, 5n….

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11
Q

Triploid

A

Three sets of chromosomes
3n…

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12
Q

Nondisjunction

A

-Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.

-Gives rise to chromosomal variation
-paired homologs fail to disjoin during segregation
-Nondisjunction occurs during meiosis I or II

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13
Q

Monosomy

A

-Loss of one chromosome
-Produces 2n-1 complement
-Although one copy remains, if the copy is lethal, organism is not viable
-Monosomy unmasks recessive alleles
-Haploinsuffciency may occur

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14
Q

Haploinsufficiency

A

When one copy is not sufficient for organism to survive

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15
Q

Trisomy

A

2n + 1 chromosomes
-Addition of chromosome produces more viable organisms
-Trisomies for autosomes are often LETHAL
-Plant trisomies are viable:
-Phenotype is altered
-Example: Datura stramonium with altered
phenotype

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16
Q

Trisomy 21: _______ Syndrome

A

Down Syndrome, trisomy of chromsome 21
-Results in an extra chromsome (three #21’s)
-On average affected individuals express 6 to 8 characterisics

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17
Q

What is DSCR?

A

Down Syndrome Critical Region
-Critical region of chromosome 21
-Genes are dosage sensitive
-Responsible for many phenotypic-associated syndromes

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18
Q

Origin of Extra 21st Chromosome?

A

-Nondisjunction of chromsome 21 during meiosis
-Homologs do not disjoin (detach) during anaphase I or II
-Leads to n +1 gametes
-Ovum is the source of 95% of trisomy cases
-Increased incidence with increasing maternal age

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19
Q

Diagnostic Testing Methods

A

1.Amniocentesis or chorionic villus sampling (CVS)

  1. NIPGD: Noninvasive prenatal genetic diagnosis
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20
Q

Explain the CVS method of Diagnostic Testing

A

Fetal cells are obtained from the amniotic fluid or chorion of the placenta

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21
Q

Explain the NIPGD method of Diagnostic Testing

A

Fetal cells and DNA obtained from maternal circulation

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22
Q

Familial Down Syndrome

A

-The translocation of chromosome 21, and occasionally runs in families

-Remember, involves translocation of chromosome 21

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23
Q

Patua syndrome

A

Trisomy 13

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24
Q

Edwards syndrome

A

-Both trisomies survive to term
-Manifest severe malformations and early lethality

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25
Q

Trisomies are often found in ….

A

-Spontaneously aborted fetuses (they make up for 20% of conceptions)

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26
Q

What doe autosomal monosomies suggest?

A

-That monosomc gamets may be functionally imparied

-they are seldom found

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27
Q

Polyploidy

A

More than two multiples of haploid chromosomes are found

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28
Q

Triploid

A

3n chromosomes

29
Q

Tetraploid

A

4n chromosomes

30
Q

Pentaploid

A

Has 5n chromosomes

31
Q

Aneuploidy

A

2n +- x chromosomes

32
Q

Disomy

A

2n

33
Q

Euploidy

A

Multiples of n

34
Q

Autopolyploidy

A

Addition of one or more sets of chromosomes identical to the haploid complement of same species

-Multiples of the same genome

35
Q

Allopolyploidy

A

Combination of chromosome sets from different species as a consequence of hybridization

36
Q

In autopolyploidy…

How does it arise? etc.

A

each identical set of chromomsomes is identical to the parents species

-Arises when:
-diploid gamete is
produced
-Two sperm fertilize on
ovum (rare)

More prevenlant in the natural population; produce balanced gametes

37
Q

Autotetraploid

A

-Chromosomes have replicated, but the parent cell never divides and instead reenters into interphase, and the chromosome number becomes doubled

-experimentally induced by colchicine

38
Q

Allopolyploidy

A

Results from hybrodizing tow closely related species

-Hybrid plant may be sterile (cannot produce vaible gametes)

-Chromosomes are not homologous
(cannot synapse in meiosis

39
Q

Allotetraploid

A

Polyploid contains equivalent of four haploid genomes derived from separate species

Original species is unknoen

40
Q

Amohidiploid

A

An allotetraploid wjere both original species are known
-These kinds of plants are found in nature

Example: Gossypium plant (cotton)

41
Q

Endopolyploidy

A

Condition where only certain cells in diploid organism are polyploid

-Set of chromosomes replicates repeatedly without nuclear division

-Can occur in cancer cells

42
Q

List the possible chromosome rearrangements:

A
  1. Deletions
  2. Duplications
  3. Inversions
  4. Nonreciprocal translocations
  5. Reciprocal translocations
43
Q

What do deletions and duplications specifically do to a chromosome?

A

Total amount of genetic information in chromosome changes

44
Q

What do inversions and translocations specifically do to a chromosome?

A

Genetic material remains the same but rearranged

45
Q

What are Deletions, or deficiency? Explain.

A

-missing regions of chromsome
-chromosome breaks in one or more places
-portion is lost

location of deletion can vary
-terminal deletion (near one end)
-intercalary deletion (interior of the chromosome)

46
Q

What is a compensation loop (Buckling out)?

A

-Synapsis between chromosome with large intercalary deletion and normal complete homolog

-Requires unpaired region of normal homolog to loop out of linear structure into deletion or compensation loop

47
Q

Cri du chat Syndrome

A

-Deletion of small terminal part of chromosome 5
-Segmental deletion
-infant exhibit anatomical malformations

48
Q

What is duplication? What does it arise from?

A

-Repeated segment of a chromosome
-a single locus is present more than once in the genome
-can produce compensation loop
-Arises from unequal crossing over between synapsed chromosome during meiosis.

49
Q

gene redundancy

A

Example: rRNA
Multiple genes perform the samejob

Multiple copies of genes encode for rRNA genes
This DNA is called rDNA

-E. Coli’s haploid genome is .7 percent rDNA (senven copies)

-Drosophila: .3 percent rDNA

50
Q

Gene amplification

A

-Another mechanims that increases rRNA

-the number of copies of a gene is increased “without a proportional increase in other genes”.

-oocytes store nutrients including ribosomes

-used by embryo in early development for rRNA synthesis

51
Q

Bar mutation in Drosophila

A

-Duplications caise phenotypic variations

-Bar-eye phenotype in Drosophila results from duplication

-Bar-eyed flies have narrow, slit-like eyes

-inhereted phenotype

-Mutation is inherited

52
Q

Gene duplication “may play a role in evolution”

A

Gene duplication is hypothesized to be a major source of new genes

Hypothesis supported by discovery of genes with substantial amount of DNA sequence in common, but distinct gene products

Ex. Genes encoding digestive enzyme trypsin and chymotrypsin

53
Q

CNVs: Copy number variants

A

Represent quantitative differences in number of large DNA sequences

-Found in coding and noncoding regions of the genome

-Play a crucial role in the expression of traits

sections of the genome are repeated and the number of repeats in the genome varies between individuals.

54
Q

Inversion

A

Rearrangement of linear gene sequence
-No loss of genetic information
-Segment of chromosome turned 180 degrees within chromosoe

-Two breaks in chromosome, and reinsertion inverted segment
-May arise from chromosomal looping

55
Q

Paracentric inversion

A

-Does not change the lengths of two arms of chromosome

-centromere is of part of inverted segment

56
Q

Pericanetric inversion

A

Centromere is part of the inverted segment
-DOES change lengths of the two arms of the chromosome

57
Q

Inversion loops

A

inverted and noninverted chromosomes in meisois paired only if they form and inversion loop

58
Q

Inversion heterozygotes

A

Organisms with one inverted chromosome and one non-inverted homolog

-can be peri or paracentric

59
Q

Paracentric inversion crossover

A

One recombinant chromatid is dicentric
-two centromeres

One is acentric
-Lacking a centromere

60
Q

Percentric inversion crossover

A

Crossover between pericentric inversion and noninverted homolog

-Recombinant chromatids have duplications and deletions

61
Q

Translocation

A

Movement of chromosomal segment to new location in genome

62
Q

Reciprocal translocation

A

Involves the exchange of segments between two nonhomologous chromosomes

-Genetic information is lost or gained

-Has unusual synapsis configuration during meiosis

63
Q

Reciprocal Translocation has two possible segregation patterns:

A

Alternate segregation:
-Segregation pattern at
first meiotic division
- Has complete
complement of genetic
information

Adjacent segregation:
-Leads to gametes containing duplications and deficiencies

if these participate in fertilization in animals, the resultant offspring do not usually survive

Parent is said to have semisterility

64
Q

Robertsonian translocation (centric fusion)

A

Involves breaks at extreme ends of short arms of two nonhomologous acrocentric chromosomes

Small segments are lost

Large submetacentric or metacentric chromosome are produces

Example: familial down syndrome

65
Q

Fragile sites

A

More susceptible to chromosome breakage when cultured in the absence of folic acid or other chemicals

-Sites indicate regions of nontightly coiled chromatin

66
Q

Fragile -X syndrome (martin-bell syndrome)

A

-Folate-sensitve site on X chromosome exhibits FXS
-Most common form of inherited mental retardation; dominant trait

-Caused by trinucleotide repeats in FMR1 gene

67
Q

Trunucleotide repeats

A

A sequences of three nucleotides in repeated many times

-Expands the size of the gene

68
Q

Genetic anticipation

A

The number of trinucleotide repeats increases with every generation

Carrier status: 55 to 230 repeats

Syndrome status: over 230 repeats

69
Q

Link between fragile site and ling cancer

A

-Defect associated with formation of tumors
-FHIT gene on fragile site location FRA3B altered or missing in lung cancer cells

-Normal protein product of this gene absent in other types of cancer cells

Biology: Genetics (7 decks)

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