Exam 2: Cytogenetic Abnormalities

Question 1

chromosomes are constantly being…

Answer 1

broken and rejoined

sometimes in the wrong way

Question 2

full breaks of both stands in dsDNA are called

Answer 2

double-strand breaks

Question 3

the cell has mechanisms for ___ repair

Answer 3

double-strand break

rejoins broken ends

Question 4

how do chromosome rearrangements arise?

Answer 4

when the wrong ends of broken chromosomes are rejoined

Question 5

major types of chromosome rearrangement

Answer 5

inversion

translocation

fusion

Question 6

which rearrangements only happen in G1 when chromosomes consist of only 1 chromatid

Answer 6

inversion

translocation

fusion

breakage

Question 7

what is an inversion

Answer 7

a piece gets turned around backwards

Question 8

what is a translocation

Answer 8

two pieces get traded between chromosomes

Question 9

what is breakage

Answer 9

a piece gets lost (lethal)

Question 10

what is fusion

Answer 10

two broken chromosomes fuse

Question 11

what does an inversion result from

Answer 11

two breaks in one chromosome with sequence reversal

Question 12

what happens if an inversion occurs inside an essential gene?

Answer 12

cell death

Question 13

do genes function if the DNA they’re located on is in either direction?

Answer 13

yes

Question 14

when does inversion cause a problem?

Answer 14

during meiosis b/c inversion loops

Question 15

inversion loop

Answer 15

pairing between inverted and normal segments

permits alignment of all homologous loci

Question 16

is an inversion loop in a bivalent a problem?

Answer 16

not unless a crossover happens inside the loop

this causes duplications and deletions

Question 17

if there is a crossover inside the inversion loop, each crossover chromatid will be…

Answer 17

duplicated for everything on one side, outside the loop

and deleted for everything on the other side, outside the loop

everything in the loop will still be present only once

Question 18

paracentric inversion

Answer 18

centromere outside loop

dicentric and acentric chromosome

Question 19

pericentric inversion

Answer 19

centromere inside loop

one centromere on each chromosome

Question 20

how are translocations like inversions

Answer 20

may have no bad effects, if no genes interrupted by breaks

cell could continue to grow and undergo mitosis

meiosis is where problems happen

Question 21

pairing at meiosis causes a…

Answer 21

pachytene cross

Question 22

adjacent disjunction types

Answer 22

I: homologous centromeres separate at MI (normal)

II: nonhomologous centromeres separate at MI (abnormal)

Question 23

adjacent disjunction always gives

Answer 23

1 good and 1 bad chromosome

gametes with duplications and deletions

Question 24

alternate disjunction

Answer 24

pachytene cross

creates 2 normal gametes and 2 balanced translocation gametes

Question 25

balanced gametes pass on the…

Answer 25

translocation

offspring are carriers of the translocation

Question 26

why are they called alternate and adjacent disjunction?

Answer 26

b/c chromosomes involved are either alternate or adjacent to each other in the pachytene cross

Question 27

when an individual has a balanced translocation he/she will produce

Answer 27

some gametes with duplications/deletions (lethal/highly abnormal)

some completely normal gametes

some gametes with the whole balanced translocation (normal phenotype)

Question 28

about 7% of families with 2 or more spontaneous abortions have…

Answer 28

a balanced translocation

Question 29

when a translocation first occurs all the original DNA is…

Answer 29

still there so it’s automatically “balanced”

Question 30

alternate disjunction can transmit the balanced translocation in normal appearing offspring…

Answer 30

forever

Question 31

some families pass on balanced translocations for…

Answer 31

generations

Question 32

ring chromosome

Answer 32

another two-break rearrangement only in G1

both tips broken off and ends are fused (forms a ring)

rare

Question 33

does a ring chromosome have all the original genes?

Answer 33

yes

Question 34

can a cell with a ring chromosome be completely normal?

Answer 34

yes, until it divides

Question 35

what is the problem with ring chromosomes

Answer 35

when sister chromatids exchange in mitosis the ring cannot divide

the centromeres oppose each other causing cell self-destruction

Question 36

do ring chromosomes retard normal growth?

Answer 36

yes, b/c in cell division the daughters often die

people with ring chromosomes are small