Exam 2: Cytogenetic Abnormalities Flashcards Preview

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Flashcards in Exam 2: Cytogenetic Abnormalities Deck (36)
1

chromosomes are constantly being...

broken and rejoined

sometimes in the wrong way

2

full breaks of both stands in dsDNA are called

double-strand breaks

3

the cell has mechanisms for ___ repair

double-strand break

rejoins broken ends

4

how do chromosome rearrangements arise?

when the wrong ends of broken chromosomes are rejoined

5

major types of chromosome rearrangement

inversion

translocation

fusion

6

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

inversion

translocation

fusion

breakage

7

what is an inversion

a piece gets turned around backwards

8

what is a translocation

two pieces get traded between chromosomes

9

what is breakage

a piece gets lost (lethal)

10

what is fusion

two broken chromosomes fuse

11

what does an inversion result from

two breaks in one chromosome with sequence reversal

12

what happens if an inversion occurs inside an essential gene?

cell death

13

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

yes

14

when does inversion cause a problem?

during meiosis b/c inversion loops

15

inversion loop

pairing between inverted and normal segments

permits alignment of all homologous loci

16

is an inversion loop in a bivalent a problem?

not unless a crossover happens inside the loop

this causes duplications and deletions

17

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

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

18

paracentric inversion

centromere outside loop

dicentric and acentric chromosome

19

pericentric inversion

centromere inside loop

one centromere on each chromosome

20

how are translocations like inversions

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

cell could continue to grow and undergo mitosis

meiosis is where problems happen

21

pairing at meiosis causes a...

pachytene cross

22

adjacent disjunction types

I: homologous centromeres separate at MI (normal)

II: nonhomologous centromeres separate at MI (abnormal)

23

adjacent disjunction always gives

1 good and 1 bad chromosome

gametes with duplications and deletions

24

alternate disjunction

pachytene cross

creates 2 normal gametes and 2 balanced translocation gametes

25

balanced gametes pass on the...

translocation

offspring are carriers of the translocation

26

why are they called alternate and adjacent disjunction?

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

27

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

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

some completely normal gametes

some gametes with the whole balanced translocation (normal phenotype)

28

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

a balanced translocation

29

when a translocation first occurs all the original DNA is...

still there so it's automatically "balanced"

30

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

forever

31

some families pass on balanced translocations for...

generations

32

ring chromosome

another two-break rearrangement only in G1

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

rare

33

does a ring chromosome have all the original genes?

yes

34

can a cell with a ring chromosome be completely normal?

yes, until it divides

35

what is the problem with ring chromosomes

when sister chromatids exchange in mitosis the ring cannot divide

the centromeres oppose each other causing cell self-destruction

36

do ring chromosomes retard normal growth?

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

people with ring chromosomes are small