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genetics > chapter 10 part 2 > Flashcards

chapter 10 part 2 Flashcards

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Biology 101 flashcards
1
Q

changes to chromosome structure can be caused by _____________ _________ or other events

A

chromosome breakage

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2
Q

what can chromosome structure mutations lead to

A

loss of gain of chromosome segments or partial deletion duplication

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3
Q

when a chromosome breaks, where are both DNA strands severed at?

A

a location called the chromosome break point

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4
Q

what can the broken ends do at the chromosome break point?

A

adhere to each other, to other broken ends, or the termini of other intact chromosomes

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5
Q

what can detachment of all or part of one chromosome arm lead to

A

a terminal deletion
-the broken fragment contains a telomere & some genetic material

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6
Q

what may be lost in terminal chromosome deletion

A

acentric since it lacks a centromere and the spindle fibers cant attach to it

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7
Q

what are organisms with one normal & one terminally deleted chromosome called?

A

partial deletion heterozygotes

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8
Q

cru-du-chat syndrome is caused by what

A

loss of 5p15.2-5p15.3
partial deletion heterozygotes

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9
Q

what is an intersitial deletion

A

the loss of an internal portion of a chromosome, & results from two chromosome breaks

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10
Q

are interstitial deletions observed in humans

A

yes

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11
Q

example of interstitial deletions

A

WAGR syndrome
-series of conditions caused by deletion of multiple genes on chromosome

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12
Q

what can unequal crossover result in

A

partial duplication on one homolog & partial deletion on the other

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13
Q

what does unequal crossover take place between

A

2 homologs

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14
Q

partial duplication heterozygote

A

organism with one normal & on duplicated homolog

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15
Q

partial deletion heterozygore

A

organism with one deleted & one normal heterozygote

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16
Q

is unequal crossover common?

A

no, it does not occur often

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17
Q

how does unequal crossover most commonly occur?

A

when repetitive regions of homologs misalign

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18
Q

ex of unequal crossover

A

williams-beuren syndrome
partial deletion heterozygotes on chromosome 7

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19
Q

what can show regions of chromosome duplication or deletion

A

microscopic observation during prophase 1 when homologs synapse

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20
Q

what creates an unpaired loop & what is it?

A

-when a large deletion or duplication creates an area of mismatch between the altered chromosome & its normal homolog
-the part of one homolog missing on the pairing partner

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21
Q

what can large deletion/duplications be detected by?

A

microscopy that reveals altered chromosome banding patterns

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22
Q

what can micro-deletions/duplications be detected by?

A

FISH
-used to detect the presence or absence of a particular DNA sequence

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23
Q

chromosome inversion

A

reattachment in the wrong orientation

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24
Q

chromosome translocation

A

reattachment to a nonhomologous chromosome

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25
Q

paracentric inversion

A

the centromere is outside of the inverted region

26
Q

pericentric inversion

A

the centromere is within the inverted region

27
Q

inversion heterozygotes

A

have one normal & one inverted homolog

28
Q

what can crossing over within a paracentric inversion result in?

A

-dicentric chromosomes (2 centromeres)
-acentric fragment (no centromere)

-dicentric chromosome is pulled toward both poles of cell & breaks
-acentric fragment is lost

29
Q

what can crossing over within a paricentric inversion result in?

A

both duplicated & deleted regions in both of the recombinant products

30
Q

what do both pericentric & paracentric inversion recombination result in?

A

two normal gametes & 2 abnormal gametes

31
Q

what are the three types of translocations

A

-nonreciprocal translocations
-reciprocal balanced translocations
-robertsonian translocations

32
Q

nonreciprocal translocations

A

(unbalanced) arise when a piece of one chromosome is translocated to a non-homolog and there is no reciprocal event
-one-way transfer

33
Q

reciprocal balanced translocations

A

-occur when pieces of two non-homologs switch places
-two-way transfers

34
Q

robertsonian translocations

A

-(chromosome fusions) involve fusion of two non-homologs
-reduction in total chromosome number

35
Q

in heterozygotes for reciprocal balances translocations, what occurs?

A

non of the four chromosomes has a fully homologous partner
so an unusual cross-like structure is formed at metaphase 1 of meiosis

36
Q

are translocation heterozygotes sterile? why?

A

they are partially sterile, only alternate segregation leads to normal gametes (& even the only 1/2 are normal)

37
Q

if two pairs of chromosomes fuse by robertsonian translocation, what happens)

A

the number of chromosomes drops to 2n-2

38
Q

what is responsible for familial down syndrome

A

one type of robertsonian translocation between chromosome 21 & (usually) chromosome 14

39
Q

what is DNA & associated proteins of a chromosome called?

A

chromatin

40
Q

what is chromatin made of

A

1/2 dna & 1/2 protein
(1/2 of protein is made of histone proteins)

41
Q

what are histone proteins

A

small basic proteins that tightly bind DNA

42
Q

what are the remaining proteins in chromatin

A

non-histone proteins
-very diverse & preform a variety of functions

43
Q

what are the five major histone proteins

A

H1, H2a, H2b, H3, & H4

44
Q

what are nucleosome core particles?

A

fundamental units of histone protein organization with two molecules of each of the histones except H1
-forms an octamer

45
Q

core DNA

A

a span of DNA about 146 bp long that wraps around each nucleosome

46
Q

nucleosome assembly

A

-H2A & H2B - dimers
-H3 & H4 - dimers
-H3-H4 dimers form a tetramer
-H2A-H2B dimer associate with the H3-H4 tetramer & form an octamer

47
Q

first level of DNA condensation

A

the wrapping of DNA around the nucleosome
-compacts the DNA about 7x

48
Q

linker DNA

A

the variable-length “string” between nucleosomes
-10 nm-fiber

49
Q

is the 10-nm fiber observed under normal cellular conditions?

A

no. a 30-nm fiber (6 times more condensed) is

50
Q

when does the 30-nm fiber form

A

when the 10-nm fiber supercoils into a solenoid structure
-6-8 nucleosomes/turn & histone H1 stabilizing the solenoid

51
Q

second level of DNA condensation

A

30nm/solenoid

52
Q

when does chromatin become maximally condensed

A

in metaphase of mitosis
-interphase chromosomes have variably sized loops of 30-nm fibers that form a 300-nm fiber

53
Q

what does chromosome shape depend on?

A

the chromosome scaffold composed of non-histone proteins

54
Q

what are chromatin loops of 20 to 100 kb anchored to the chromosome scaffold by? at sites called what?

A

by nonhistone proteins at sites called MARs (matrix attachment regions)
-metaphase chromatin is compacted 250-fold compared to the 300-nm fiber

55
Q

what does chromosome compaction allow for?

A

efficient separation of chromosomes at anaphase

56
Q

what do the chromatin loops formed during condensation play a role in?

A

regulation of gene expression

57
Q

where does active transcription tale place in?

A

segments of loops away from MARs

58
Q

what must happen as the replication fork passes

A

nucleosomes must break down into component parts & release the DNA

59
Q

what happens after replication

A

the nucleosomes are reassembled, but we need 2X as many now

60
Q

Nucleosomes present after replication typically contain:

A

-some old histone proteins (epigientic marks)
-some new histone proteins
-H3 & J4 tetrameres reassociate randomly with one of the sister chromatids
-H2A & H2B dimers disassemble & are reassembled from both old & new histones

genetics (23 decks)

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