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2014 Genetics Topic 1:CM > L9 > Flashcards

L9 Flashcards

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1
Q

how do chromosome mutations occur

A

due to change in chromosome number and structure

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2
Q

what are the four main types of structural mutation

A

deletion, inversion, duplication and translocations

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3
Q

what are deletions

A

are the result of a loss of a chromosome segment and when homozygous are usually really lethal

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4
Q

What are duplications

A

are the result of the addition of an extra copy of a chromosome region

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5
Q

true or false, both duplications and deletions are rare in nature

A

true, especially in diploid organism

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6
Q

what are inversions

A

involves two breaks in the chromosome and a 180 degrees turn, ligated once more into the same chromosome it broke off from; relatively common

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7
Q

what are the two types of inversion

A

paracentric and pericentric

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8
Q

what is paracentric inversion

A

includes the centromere during an inversion

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9
Q

what is pericentric

A

do not include the centromere during an inversion

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10
Q

why chromosome mutations important (5)

A
  • allow us to understand how genes work together in the genome
  • provide insights into meiosis and chromosome architecture
  • have proven useful tools for genomic manipulation
  • cause of some genetic diseases in humans
  • have revealed insights into evolutionary processes
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11
Q

what are structural mutations

A

involve novel sequence rearrangements within one or more DNA molecules

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12
Q

true or false, changes in the number of chromosomes are not associated with the alterations in the DNA molecules

A

true

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13
Q

true or false, both changes in the chromosome number and chromosome structure can occur spontaneously and can also be induced by both chemical and physical mutagens

A

true

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14
Q

true or false, double stranded breaks are lethal unless repaired

A

true; repair mechanisms in cell correct double stranded breaks by joining broken ends together; if the ends of two different chromosome ends are joined then chromosomal rearrangement can occur

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15
Q

true or false, only DNA molecules with a centromere and two telomeres will survive meiosis

A

true

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16
Q

what is non allelic homologous recombination ( can produce the 4 types of structural mutation)

A

In organisms with repeat DNA sequences within one chromosome or on different chromosomes non homologous crossing over can occur; if repeats pair that are not on the same position on homologs, crossing over can produce rearrangements

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17
Q

what is a deletion

A
  • simply the loss of part of a chromosome; the process of deletion usually requires two chromosomal breaks to cut out of the intervening segment (the segment will be lost because it does not have a centromere)
18
Q

what are the two places of deletion

A

terminal or interstitial

19
Q

what is a terminal deletion

A

deletion at the end of a chromosome

20
Q

what is interstitial deletion

A

within a chromosome arm; occurs after two breaks occur and the ends rejoin

21
Q

what does the magnitude of deletion on the chromosome depend on

A

size of the fragment deleted

22
Q

what are the two types of deletion

A

intragenic and multigenic

23
Q

what is intragenic deletion

A

intragenic deletion is a small deletion within a gene that inactivates the gene

24
Q

what is multigenic deletion

A

multigenic deletion involves several or many genes and their consequences are more severe

25
Q

what does a deletion heterozygote chromosome form

A

forms a loop

26
Q

true or false, if multigenic deletion is made homozygous by inbreeding the consequence is always lethal

A

true

27
Q

true or false, multigenic deletions never revert back to the wild type

A

true

28
Q

how does pseudodominance occur

A

when deletions allow for the expression of phenotypes carried as recessive alleles

29
Q

what is a duplication

A

a duplication is a mutation with an extra copy of a chromosome region

30
Q

true or false, duplication is an effective mechanism for increasing the number of copies of genes and also the genome size

A

true

31
Q

how does positional effect affect a Drosophila fly

A

Occasionally a fly carries three copies of the duplication on its X chromosome (double bar) the eye is extremely reduced; due to its eyes having a reduced number of facets

32
Q

how does the Bar mutation result

A

results from a small duplication on the X chromosome

33
Q

true or false, the Bar mutation is inherited as an incomplete or partial dominant X linked trait

A

true

34
Q

what is a inversion

A

Inversions involve two chromosome breaks in the same chromosome, the region is flipped and re-inserted

35
Q

why are individuals with inversions usually look normal

A

this is because inversions do not change the amount of genetic information of the individual

36
Q

what is an inversion heterozygote

A

cells containing one normal and one chromosome carrying the inversion

37
Q

how is an inversion loop formed

A

in meiosis one chromosome twists at the ends of the inversions so that it can pair with the untwisted homolog

38
Q

how are dicentric bridges and acentric fragment formed

A

in paracentric inversion crossing over within the inversion loop causes a dicentric bridge and an acentric fragment to form

39
Q

what happens in pericentric inversions crossing over in inversion loop

A

can result in duplications and deletions

40
Q

what is the result of paracentric inversion crossing over

A

we will result in our two starting products

41
Q

true or false, inversions appear to act as cross over suppressors

A

true; due to resulting non viable gametes which make it seem as if no crossing over has occurred

42
Q

true or false, inversions can lead to the creation of super genes

A

true; this is because those genes are locked together because cross over cannot break them up; those genes will remain in inversion

2014 Genetics Topic 1:CM (11 decks)

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