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genetics > chapter 10 part 2 > Flashcards

chapter 10 part 2 Flashcards

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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
what can large deletions/duplications be detected by
microscopy that reveals altered chromosome banding patterns
26
can you use microscopy to detect micro-deletions/duplications
no - too small
27
what is usually used to detect micro-deletions/duplications
molecular techniques such as FISH (fluorescent in situ hybridization) - detects presence or absence of particular DNA sequence
28
chromosome inversion
reattachment of broken chromosome fragment in wrong orientation
29
chromosome translocation
reattachment of broken chromosome fragment to non homologous chromosome
30
paracentric inversion
if centromere is outside of inverted region
31
pericentric inversion
if centromere is within inverted region
32
inversion heterozygotes
have one normal and one inverted homolog
33
crossing over that occurs within a paracentric inversion results in:
- dicentric chromosome: contains 2 centromeres - acentric fragment: doesn't contain centromere
34
what happens to dicentric chromosome in paracentric inversion
pulled toward both poles of cell, eventually breaks at random point - both produces of break are missing genetic material
35
what happens to acentric fragment during paracentric inversion
lost because it lacks centromere and can't attach to spindle during division
36
crossing over within pericentric inversion results in:
both duplicated and deleted regions in both of the recombinant products
37
recombination events of paracentrics/pericentric inversions yields:
1. 2 normal gametes (non-crossover chromatids) 2. 2 abnormal gametes (crossover chromatids)
38
3 types of translocations
1. nonreciprocal 2. reciprocal 3. Robertsonian
39
nonreciprocal translations
piece of one chromosome is translocated to a non-homolog and there is no reciprocal event - one-way transfer
40
reciprocal translocation
pieces of 2 non-homologs switch places - two-way transfer
41
Robertsonian translocations
chromosome fusions - involve fusion of 2 non-homologs - reduction in total chromosome number
42
in heterozygotes for reciprocal balanced translocations, none of four chromosomes has what?
fully homologous partner
43
what is formed at metaphase 1 of meiosis in reciprocal balanced translocations
unusual cross-like structure
44
what are translocations heterozygotes in reciprocal translocations
semi-sterile
45
why are translocations heterozygotes in reciprocal translocations semi-sterile
only alternate segregation leads to normal gametes - even only 1/2 of them are normal
46
when 2 pairs of chromosome fuse by Robertsonian translocation, number of chromosomes drops to
2n-2
47
ex. of Robertsoninan translocation
familial Down Syndrome
48
familial Down Syndrome
Roberstonian translocation between chromosome 21 and usually 14
49
chromatin
DNA and associated proteins of a chromosome
50
what is chromatin organization essential for
- gene regulation - segregation
51
chromatin =
1/2 DNA 1/2 proteins
52
protein =
1/2 histone proteins 1/2 non-histone proteins
53
histone proteins
small basic proteins that tightly bind DNA
54
non-histone proteins
rumination proteins that are very diverse and perform a variety of functions
55
5 major histone proteins
1. H1 2. H2A 3. H2B 4. H3 5. H4
56
nucleosome core particle
fundamental units of histone protein organization with 2 molecules each of histones (H2A, H2B, H3, and H4) that form ocatmer
57
core DNA
~146 bp long span of DNA that wraps around each octamer to form a nucleosome
58
nucleosome assembly
- 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
first level of DNA condensation
wrapping of DNA around the nucleosome - compacts DNA 7x
60
electron micrographs of DNA in least condensed state show:
10-nm fiber - beads-on-a-string
61
linker DNA
variable-length string between nucleosomes
62
linker DNA length in Saccharomyces cerevisiae
13-18 bp
63
linker DNA length in Drosophila
35 bp
64
linker DNA length in humans/mammals
40-50 bp
65
linker DNA length in sea urchins
110 bp
66
when is the 10-nm fiber not observed
under normal cellular conditions
67
what is observed instead of a 10-nm fiber
30-nm fiber (6 times more condensed)
68
how does 30-nm fiber form
when 10-nm fiber coils into a solenoid structure
69
solenoid structure
6-8 nucleosomes per turn, histone H1 stabilizes solenoid
70
second level of DNA condensation
30nm fiber - solenoid
71
when does chromatin become maximally condensed
during metaphase of mitosis
72
interphase chromosomes have variably sized loops of 30-nm fibers that form a
300-nm fiber
73
chromosome shape depends on the
chromosome scaffold
74
chromosome scaffold
composed of filamentous, non-histone proteins
75
MARs (matrix attachment regions)
where chromatin loops (20-100kb) are anchored to chromosome scaffold by non-histone proteins
75
76
metaphase chromatin is compacted _____________ compared to the 300-nm fiber
250-fold
77
what does chromosome compaction allow for
efficient separation of chromosomes at Anaphase
78
chromatin loops formed during condensation play role in what?
regulation of gene expression
79
where does active transcription usually occur
in segments of loops away from MARs - DNA near MARs less accessible
80
as the replication fork passes, what must happen to nucleosomes
must break down into component parts and release DNA
81
after replication, what happens to the nucleosomes?
reassembled, but need 2X now
82
nucleosomes present after replication typically contain:
- 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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