Chromosomal mutation

Question 1

types of chromosomal mutations

Answer 1

rearrangements
aneuploids
polyploids

Question 2

types of rearrangements

Answer 2

duplication
deletion
inversion
translocation

Question 3

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

Answer 3

deletion

Question 4

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

Answer 4

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

Question 5

tandem vs displaced duplication

Answer 5

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

Question 6

reverse duplication

Answer 6

segment flipped over

Question 7

duplications in meiosis-pairing

Answer 7

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

Question 8

why do duplications alter phenotype

Answer 8

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

Question 9

cause of duplication and deletion

Answer 9

unequal crossing over

Question 10

unbalanced gene dosage

Answer 10

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

Question 11

segmental duplications

Answer 11

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

Question 12

deletions in prophase 1

Answer 12

heterozygote
loop forms for homologous sequences to align

Question 13

cause of inversions

Answer 13

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

Question 14

paracentric inversion vs pericentric inversion

Answer 14

centromere unaffected vs centromere affected

Question 15

why do inversions affect fitness

Answer 15

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

Question 16

variegation

Answer 16

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

Question 17

paracentric inversions in prophase 1for a heterozygote

Answer 17

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

Question 18

anaphase 1 for paracentric inversion

Answer 18

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

Question 19

gamete result from paracentric inversion

Answer 19

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

Question 20

prophase 1 pericentric inversions (heterozygote)

Answer 20

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

Question 21

anaphase 1 + 2 and gamete results for pericentric inversion

Answer 21

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

Question 22

translocation

Answer 22

movement of material between non homologous chromosomes

Question 23

non reciprocal vs reciprocal translocation

Answer 23

unidirectional (unusual) vs both directions

Question 24

robertstonian translocation

Answer 24

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

Question 25

acrocentric chromosome

Answer 25

centromere towards end (long and short arm)

Question 26

metacentric chromosome

Answer 26

centromere near middle

Question 27

fitness effects of translocations

Answer 27

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

Question 28

types of aneuploidy

Answer 28

nullisomy monosomy trisomy tetrasomy

Question 29

nullisomy

Answer 29

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

Question 30

monosomy

Answer 30

loss of a single chromosome 2n-1

Question 31

trisomy

Answer 31

gain of a single chromosome 2n+1

Question 32

tetrasomy

Answer 32

gain of two homologous chromosomes 2n+2

Question 33

causes of aneuploidy

Answer 33

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

Question 34

non disjunction

Answer 34

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

Question 35

gamete result in first division nondisjunction vs second division nondisjunction

Answer 35

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

Question 36

increasing chromosome size...

Answer 36

aneuploidy more deleterious fewer live births

Question 37

primary down syndrome

Answer 37

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

Question 38

cohesin

Answer 38

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

Question 39

reduced cohesin

Answer 39

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

Question 40

how can translocation cause down syndrome

Answer 40

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

Question 41

polyploidy

Answer 41

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

Question 42

autopolyploidy

Answer 42

all chromosomes a gamete receives are from a single species

Question 43

allopolyploidy

Answer 43

chromosomes are from two species

Question 44

how autopolyploidy arises

Answer 44

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

Question 45

autotriploids

Answer 45

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

Question 46

how allopolyploids arise

Answer 46

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