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genetics > chapter 10 part 2 > Flashcards

chapter 10 part 2 Flashcards

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Biology 101 flashcards
1
Q

mutations that result in loss or gain of whole chromosomes or chromosome segments can produce what?

A

severe abnormalities due to gene dosage imbalances

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2
Q

terminal chromosome deletion

A
  • single break point
  • detachment of one part of chromosome arm
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3
Q

chromosome break point

A

both DNA strands severed at a location called a chromosome break point

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4
Q

where can broken chromosome ends adhere to

A
  • other broken ends
  • termini or other intact chromosomes
  • each other
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5
Q

broken fragment in terminal deletion contains what?

A

telomere and some genetic material

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6
Q

what happens if broken chromosome fragment is acentric?

A

will likely be lost during cell division as it can’t attach to spindle apparatus

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7
Q

partial deletion heterozygote

A

one normal and one terminally deleted chromosome

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8
Q

ex. of terminal deletion

A

Cri-du-chat syndrome

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9
Q

Cri-du-chat syndrome

A

caused by loss of 5p15.2-5p15.3
- infants produce distinctive cat-cry sound

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10
Q

interstitial deletion

A

loss of an internal portion of a chromosome
- 2 chromosome breaks

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11
Q

ex. of interstitial deletion

A

WAGR syndrome

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12
Q

WAGR syndrome

A

series of conditions caused by deletion of multiple genes on chromosome 11

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13
Q

what can unequal crossover result in

A

partial duplication or partial deletion

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14
Q

partial duplication heterozygote

A

one normal and one duplication homolog

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15
Q

partial deletion heterozygote

A

one normal and one deleted homolog

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16
Q

true or false: unequal crossover occurs often

A

false

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17
Q

when does unequal crossover usually occur

A

when repetitive regions of homologs misalign

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18
Q

ex. of unequal crossover

A

Williams-Beuren syndrome

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19
Q

is Williams-Beuren syndrome partial deletion or partial duplication

A

partial deletion

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20
Q

Williams-Beuren syndrome

A

partial deletion heterozygotes for segment of chromosome 7 that contains copies of gene PMS (A and B)
- unequal crossover leads to one nonfunctional hybrid PMSA-PMSB gene

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21
Q

when do homologs synapse

A

prophase 1

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22
Q

what can be observed through microscopic observation during prophase 1

A

regions of chromosome duplication and deletion

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23
Q

a large deletion or duplication creates what

A

area of mismatch between altered chromosome and normal homolog

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24
Q

unpaired loop

A

created by large deletion/duplication, which is the part of one homolog missing on the pairing partner

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25
Q

what can large deletions/duplications be detected by

A

microscopy that reveals altered chromosome banding patterns

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26
Q

can you use microscopy to detect micro-deletions/duplications

A

no - too small

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27
Q

what is usually used to detect micro-deletions/duplications

A

molecular techniques such as FISH (fluorescent in situ hybridization)
- detects presence or absence of particular DNA sequence

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28
Q

chromosome inversion

A

reattachment of broken chromosome fragment in wrong orientation

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29
Q

chromosome translocation

A

reattachment of broken chromosome fragment to non homologous chromosome

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30
Q

paracentric inversion

A

if centromere is outside of inverted region

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31
Q

pericentric inversion

A

if centromere is within inverted region

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32
Q

inversion heterozygotes

A

have one normal and one inverted homolog

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33
Q

crossing over that occurs within a paracentric inversion results in:

A
  • dicentric chromosome: contains 2 centromeres
  • acentric fragment: doesn’t contain centromere
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34
Q

what happens to dicentric chromosome in paracentric inversion

A

pulled toward both poles of cell, eventually breaks at random point
- both produces of break are missing genetic material

35
Q

what happens to acentric fragment during paracentric inversion

A

lost because it lacks centromere and can’t attach to spindle during division

36
Q

crossing over within pericentric inversion results in:

A

both duplicated and deleted regions in both of the recombinant products

37
Q

recombination events of paracentrics/pericentric inversions yields:

A
  1. 2 normal gametes (non-crossover chromatids)
  2. 2 abnormal gametes (crossover chromatids)
38
Q

3 types of translocations

A
  1. nonreciprocal
  2. reciprocal
  3. Robertsonian
39
Q

nonreciprocal translations

A

piece of one chromosome is translocated to a non-homolog and there is no reciprocal event
- one-way transfer

40
Q

reciprocal translocation

A

pieces of 2 non-homologs switch places
- two-way transfer

41
Q

Robertsonian translocations

A

chromosome fusions - involve fusion of 2 non-homologs
- reduction in total chromosome number

42
Q

in heterozygotes for reciprocal balanced translocations, none of four chromosomes has what?

A

fully homologous partner

43
Q

what is formed at metaphase 1 of meiosis in reciprocal balanced translocations

A

unusual cross-like structure

44
Q

what are translocations heterozygotes in reciprocal translocations

A

semi-sterile

45
Q

why are translocations heterozygotes in reciprocal translocations semi-sterile

A

only alternate segregation leads to normal gametes
- even only 1/2 of them are normal

46
Q

when 2 pairs of chromosome fuse by Robertsonian translocation, number of chromosomes drops to

A

2n-2

47
Q

ex. of Robertsoninan translocation

A

familial Down Syndrome

48
Q

familial Down Syndrome

A

Roberstonian translocation between chromosome 21 and usually 14

49
Q

chromatin

A

DNA and associated proteins of a chromosome

50
Q

what is chromatin organization essential for

A
  • gene regulation
  • segregation
51
Q

chromatin =

A

1/2 DNA
1/2 proteins

52
Q

protein =

A

1/2 histone proteins
1/2 non-histone proteins

53
Q

histone proteins

A

small basic proteins that tightly bind DNA

54
Q

non-histone proteins

A

rumination proteins that are very diverse and perform a variety of functions

55
Q

5 major histone proteins

A
  1. H1
  2. H2A
  3. H2B
  4. H3
  5. H4
56
Q

nucleosome core particle

A

fundamental units of histone protein organization with 2 molecules each of histones (H2A, H2B, H3, and H4) that form ocatmer

57
Q

core DNA

A

~146 bp long span of DNA that wraps around each octamer to form a nucleosome

58
Q

nucleosome assembly

A
  • histones H2A/B assemble into dimers
  • histones H3/H4 assemble into dimers
  • 2 H3/4 dimers = tetramer
  • 2 H2A/B dimers associate with tetramer to form octamer
59
Q

first level of DNA condensation

A

wrapping of DNA around the nucleosome
- compacts DNA 7x

60
Q

electron micrographs of DNA in least condensed state show:

A

10-nm fiber
- beads-on-a-string

61
Q

linker DNA

A

variable-length string between nucleosomes

62
Q

linker DNA length in Saccharomyces cerevisiae

A

13-18 bp

63
Q

linker DNA length in Drosophila

A

35 bp

64
Q

linker DNA length in humans/mammals

A

40-50 bp

65
Q

linker DNA length in sea urchins

A

110 bp

66
Q

when is the 10-nm fiber not observed

A

under normal cellular conditions

67
Q

what is observed instead of a 10-nm fiber

A

30-nm fiber (6 times more condensed)

68
Q

how does 30-nm fiber form

A

when 10-nm fiber coils into a solenoid structure

69
Q

solenoid structure

A

6-8 nucleosomes per turn, histone H1 stabilizes solenoid

70
Q

second level of DNA condensation

A

30nm fiber - solenoid

71
Q

when does chromatin become maximally condensed

A

during metaphase of mitosis

72
Q

interphase chromosomes have variably sized loops of 30-nm fibers that form a

A

300-nm fiber

73
Q

chromosome shape depends on the

A

chromosome scaffold

74
Q

chromosome scaffold

A

composed of filamentous, non-histone proteins

75
Q

MARs (matrix attachment regions)

A

where chromatin loops (20-100kb) are anchored to chromosome scaffold by non-histone proteins

75
Q
A
76
Q

metaphase chromatin is compacted _____________ compared to the 300-nm fiber

A

250-fold

77
Q

what does chromosome compaction allow for

A

efficient separation of chromosomes at Anaphase

78
Q

chromatin loops formed during condensation play role in what?

A

regulation of gene expression

79
Q

where does active transcription usually occur

A

in segments of loops away from MARs
- DNA near MARs less accessible

80
Q

as the replication fork passes, what must happen to nucleosomes

A

must break down into component parts and release DNA

81
Q

after replication, what happens to the nucleosomes?

A

reassembled, but need 2X now

82
Q

nucleosomes present after replication typically contain:

A
  • some old histone proteins (may have epigenetic marks like methyl/acetyl)
  • new histone proteins
  • H3/H4 tetramers reassociated randomly with one of sister chromatids
  • H2A/B dimers disassemble and are reassembled from both old/new histones

genetics (47 decks)

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