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Genetics > Lecture 9 - Chromosomal Abnormalities > Flashcards

Lecture 9 - Chromosomal Abnormalities Flashcards

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1
Q

What are the three types of chromosome mutations

A

rearrangements, aneuploids, polyploids

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2
Q

What do chromosome rearrangements do generally

A

alter the structure of chromosomes

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3
Q

What are the 4 types of chromosome rearrangements

A

duplications, deletions, inversions, translocations

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4
Q

What is the definition of an aneuploid

A

they have an altered number of chromosomes in terms of being added or deleted

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5
Q

What is the definition of a polyploid

A

one or more complete sets of chromosomes are added or deleted

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6
Q

What is the definition of duplications and what are the two types

A

segment of a chromosome is duplicated
Tandem duplications
Displaced duplications

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7
Q

What is the definition of a tandem duplication

A

duplicated regions are adjacent to the original section

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8
Q

What is the definition of a displaced duplication

A

duplicated region is elsewhere in the genome

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9
Q

What is the outcome of homozygous duplications during replication

A

not a problem during replication

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10
Q

What is the outcome of heterozygous duplications during replication

A

chromosomes are not the same length, the duplicated chromosome has to form an inversion loop so regions can line up

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11
Q

Define unbalanced gene dosage

A

if genes are duplicated it can lead to a greater production of those gene products which can affect phenotype

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12
Q

What percentage of human genome contains segmental duplications

A

4%

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13
Q

Explain the role of duplication in evolution

A
  • existing copies of a gene are not free to vary if encoding something essential
  • if that gene gets duplicated extra copies can undergo mutation and change
  • over time extra copy might acquire enough mutations to assume new function to organism
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14
Q

Define a deletion

A

segment of chromosome is deleted

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15
Q

What are the effects of heterozygous chromosomes concerning a deletion during replication

A

the longer wild type chromosome must form an inversion loop to line up with the chromosome with a deletion

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16
Q

What are the effects of a homozygous deletion

A

It is lethal in the homozygous due to loss of essential genes

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17
Q

Define haploinsufficient and what type of chromosomal rearrangement is it associated with

A

Associated with deletions when a single copy of a gene is not sufficient to produce a wile type phenotype

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18
Q

Define inversions and what are the two types

A

when chromosome segment gets inverted
paracentric inversions
Pericentric inversions

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19
Q

What are paracentric inversions

A

inversions do not span the centromere

20
Q

what are pericentric inversions

A

inversions do span the centromere

21
Q

What are the effects of inversion on phenotype

A

typically profound effect

can disrupt gene or gene order

22
Q

Does a homozygous individual for a particular inversion have problems in meiosis

A

no problems

23
Q

Does a heterozygous individual for a particular inversion have problems in meiosis

A

Yes needs a 4 strand inversion loop

24
Q

What are the results in the gametes of a heterozygous paracentric person where the chromosomes have crossed over in the inversion loop

A

1 non-recombinant gamete with no inversion
2 recombinant short nonviable gametes
1 non-recombinant gamete with paracentric inversion

25
Q

What are the results in the gametes of a heterozygous pericentric person where the chromosomes have crossed over in the inversion loop

A

1 non recombinant gamete with no inversion
2 recombinant long nonviable gametes
1 non recombinant gamete with pericentric inversion

26
Q

What is distinguishable between paracentric and pericentric inversions during crossing over in meiosis

A

Paracentric inversion leads to formation of a dicentric chromatid and an acentric chromatid

27
Q

What is the definition of a dicentric chromatid

A

has two centromeres

28
Q

What is the definition of an acentric chromatid

A

lacks a centromere

29
Q

What is the definition of a translocation

A

movement of genetic material between non homologous chromosomes or within the same chromosome

30
Q

What are the effects of translocations

A

link genes that were originally located on different chromosomes
can disrupt gene sequences

31
Q

Define robertsonian translocation and what is the overall result on the genome

A

deletion associated with translation where two long arms are joined together and two short arms are joined and lost
Overall result is a reduction in chromosome number by 1

32
Q

Can aneuploidy happen in meiosis or mitosis

A

both

33
Q

can aneuploidy happen in meiosis I or II

A

both

34
Q

What are the 3 specific ways that aneuploidy can happen

A
  1. centromere gets deleted
  2. small chromosome lost in robertsonian translocation
  3. nondisjunction and failure of homologous chromosomes or sister chromatids to separate
35
Q

What are the 4 types of aneuploidy and what is the math that goes with them

A

nullisomy 2n-2
Monosomy 2n-1
trisomy 2n+1
tetrasomy 2n+2

36
Q

What are the rates of aneuploidy in human pregnancy

A

30% of conceptions aborted and 50 % of those due to aneuploidy

37
Q

What causes trisomy 21

A

nondisjunction in oogenisis

38
Q

Primary down syndrome is what

A

not heritable resulting from spontaneous nondisjunction in oogenisis

39
Q

What is maternal age linked to increased rates of down syndrome

A

oocytes suspended in diplotene for a long period of time start to have cohesin in spindle structure break down leading to nondisjunction of chromosomes.

40
Q

What is the definition of familial down syndrome

A

Parents who are carriers of chromosomes which have undergone robertsonian translocation
Long arm of 21 and 14 join together
Gametes can segregate 6 different ways, 3 of which will cause a live birth , 1 of those ways leads to down syndrome`

41
Q

What are the two types of polyploidy

A

autopolyploidy and allopolyploidy

42
Q

Define autopolyploidy

A

ploidy event that derives from a single species caused by accidents in mitosis or meiosis

43
Q

Define allopolyploidy

A

arises from hybridization between two species where one species carries chromosome sets from two or more species

44
Q

What ploidy are allopolyploidy hybrids

A

diploid

45
Q

Cell volume is correlated to what

A

nuclear volume

Genetics (9 decks)

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