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SL12003 Genetics > Chromosomal mutation > Flashcards

Chromosomal mutation Flashcards

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1
Q

types of chromosomal mutations

A

rearrangements
aneuploids
polyploids

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2
Q

types of rearrangements

A

duplication
deletion
inversion
translocation

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3
Q

is a duplication or deletion of the same region of a chromosome more harmful

A

deletion

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4
Q

intra chromosomal duplications vs inter chromosomal duplications and which is more common

A

same chromosome vs when the new copy goes onto a different chromosome
intra more common

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5
Q

tandem vs displaced duplication

A

duplication occurs next to each other vs new copy elsewhere in genome

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6
Q

reverse duplication

A

segment flipped over

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7
Q

duplications in meiosis-pairing

A

in an individual heterozygous for a duplication, the duplicated chromosome loops out during pairing in prophase 1

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8
Q

why do duplications alter phenotype

A

dosage effects-unbalanced gene dosage
position in genome also influences genotype

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9
Q

cause of duplication and deletion

A

unequal crossing over

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10
Q

unbalanced gene dosage

A

leads to developmental abnormalities
relative dosage of proteins/gene products that interact thought to be important
protein complexes effected

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11
Q

segmental duplications

A

duplications longer than 1000bp (less than 1000 is an indel)
detected by sequencing

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12
Q

deletions in prophase 1

A

heterozygote
loop forms for homologous sequences to align

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13
Q

cause of inversions

A

region between two breaks in a chromosome is flipped before the breaks are repaired

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14
Q

paracentric inversion vs pericentric inversion

A

centromere unaffected vs centromere affected

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15
Q

why do inversions affect fitness

A

affects positions of promoters and chromatin structure
eg inversion could move a gene near heterochromatin
breaks genes
relative order of genes influences how they are expressed (position effects)
disrupts meiosis is pericentric

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16
Q

variegation

A

variation in the phenotype that can be caused by somatic mutations or transposable elements

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17
Q

paracentric inversions in prophase 1for a heterozygote

A

inversion loop forms
single cross over within inverted region
unusual structure forms
one of the four chromatids now has two centromeres and the other lacks a centromere

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18
Q

anaphase 1 for paracentric inversion

A

centromeres separate, stretching dicentric chromatid (forms dicentric bridge) causing it to break. chromosome lacking a centromere is lost.

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19
Q

gamete result from paracentric inversion

A

2 gametes: wild type non recombinant chromosomes. one is normal, the other has the paracentric inversion
2 gametes: recombinant chromosomes missing some genes. Nonviable

20
Q

prophase 1 pericentric inversions (heterozygote)

A

inversion loop forms
crossing over within inverted region
two chromatids have too many copies of some genes and no copies of others

21
Q

anaphase 1 + 2 and gamete results for pericentric inversion

A

chromosomes separate
chromatids separate
1. normal non recombinant gamete
2. two non viable recombinant gametes as too many/too few of genes
3. non recombinant gamete with pericentric inversion
same length

22
Q

translocation

A

movement of material between non homologous chromosomes

23
Q

non reciprocal vs reciprocal translocation

A

unidirectional (unusual) vs both directions

24
Q

robertstonian translocation

A

reciprocal
short arm of one acrocentric chromosome is exchanged with long arm of another
creates a metacentric chromosome and a fragment that fails to segregate so is lost

25
Q

acrocentric chromosome

A

centromere towards end (long and short arm)

26
Q

metacentric chromosome

A

centromere near middle

27
Q

fitness effects of translocations

A

cut within genes-can find which genes cause diseases
position effects
associated with loss of genes, eg roberstonians

28
Q

types of aneuploidy

A

nullisomy
monosomy
trisomy
tetrasomy

29
Q

nullisomy

A

loss of both members of a homologous pair of chromosomes
2n-2

30
Q

monosomy

A

loss of a single chromosome
2n-1

31
Q

trisomy

A

gain of a single chromosome
2n+1

32
Q

tetrasomy

A

gain of two homologous chromosomes
2n+2

33
Q

causes of aneuploidy

A

deletion of centromere during mitosis and meiosis
roberstonian translocation
nondisjunction during meiosis and mitosis
normally in mitosis (somatic mutations)

34
Q

non disjunction

A

failure of a pair of chromosome to separate during anaphase
more common in first meiotic division
gametes have extra or missing chromosomes

35
Q

gamete result in first division nondisjunction vs second division nondisjunction

A

gametes have extra or missing chromosome vs gametes have extra chromosome, missing chromosome or normal number of chromosomes

36
Q

increasing chromosome size…

A

aneuploidy more deleterious
fewer live births

37
Q

primary down syndrome

A

3 copies of chromosome 21
mainly caused by spontaneous non disjunction, mainly in egg
incidence increases with maternal age

38
Q

cohesin

A

forms a protein complex to keep chromosomes together
aids in proper alignment and segregation of sister chromatids
cross over keeps them together

39
Q

reduced cohesin

A

destabilizes homologous chromosome pairing, leading to fewer or improperly formed crossovers.
errors in segregation-non disjunction can occur

40
Q

how can translocation cause down syndrome

A

chromosome 21 translocated onto another chromosome
eg long arm of 21 attached to 14
the person with this karotype is a carrier but at increased risk of having children with down syndrome

41
Q

polyploidy

A

organism has more than two complete sets of chromosomes
more common in plants
associated with increased cell size

42
Q

autopolyploidy

A

all chromosomes a gamete receives are from a single species

43
Q

allopolyploidy

A

chromosomes are from two species

44
Q

how autopolyploidy arises

A

mitotic nondisjunction
failure of cytokinesis leads to autotetraploids
nondisjunction in germ line the gametes will be diploid and when they mate with normal haploid gamete a triploid forms
meiotic non disjunction

45
Q

autotriploids

A

non viable
homologous chromosomes can pair or not pair in 3 ways
resulting gametes have extra chromosomes or lack chromosomes

46
Q

how allopolyploids arise

A

hybridisation between two species, followed by chromosome doubling

hybrid produced by 2 different species has nonhomologous chromosomes that cant pair properly forming unbalanced, nonviable gametes
nondisjunction leads to doubling of the chromosomes=allotetraploid
chromosome pairing and segregation are normal and produce viable gametes

SL12003 Genetics (11 decks)

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