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MLSCI 480 > Prenatal Genetics > Flashcards

Prenatal Genetics Flashcards

1
Q

chromatin composed of …

A

DNA, histones, and other proteins

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2
Q

chromosomes are made of …

A

chromatin

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3
Q

chromatin plays an important role in…

A

DNA compaction as well as regulating replication, transcription, recombination, and chromosome segregation

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4
Q

nucleosome cores are joined by …

A

linker DNA
- 34 bp
- nucleosome consists of a histone octamer, 147 bp of DNA wrapped around the octamer and linker DNA

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5
Q

a nucleosome histone core is composed of ___ histones

A

8

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6
Q

each nucleosome histone cor contains two of the following histones:

A

H2A, H2B, H3, H4

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7
Q

nucleosome core DNA is comprised of ____ bpm which wrapped around the histone octamer

A

147

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8
Q

nucleosome functions

A
  • facilitates compaction of ~200 bp of DNA
  • facilitates compaction of 30 nm chromatin fibre
  • template for chromatin enzymes which facilitate post-translational modifications
  • PTM facilitates higher levels of compaction
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9
Q

what is a chromatosome?

A

consists of a nucleosome and a linker histone

histone protein H1 may bind to linker DNA and protect an additional 15 to 20 bp of DNA

H1 bind at the DNA entering and exiting the nucleosome

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10
Q

most common linker histone

A

H1

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11
Q

heterochromatin

A

eukaryotic chromatin that remains tightly compacted during interphase and is not transcribed

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12
Q

telomere

A

end of a chromosome composed of repeated DNA sequences and associated proteins

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13
Q

p arm =

A

petite; short arm
placed at top

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14
Q

q arm =

A

long arm
bottom

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15
Q

centromere

A

appears as a constriction in metaphase chromosomes
- composed of repeated sequences in the ara of the chromosome that attaches to the mitotic spindle

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16
Q

satellite

A

part of the end of a chromosome that is separated from the rest of the chromosome by a secondary constriction

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17
Q

metacentric

A

centromere located centrally, p and q arms are approx. same length

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18
Q

sub metacentric

A

centromere located off center
q arm slightly longer than p arm

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19
Q

acrocentric

A

cetromere located nearer one end of the chromosome; q arm significantly larger than p arm

20
Q

telocentric

A

centromere is the distal end of the chromosome
no p arm
not normally found in humans

21
Q

MLPA

A

multiplx ligation-dependent probe amplification
- propietary technique developed by MRC Holland

22
Q

applications of MLPA

A
  • includes detection of deletions, duplications, and aneuploidies
  • more sensitive for detecting insertions(?) and deletions
23
Q

MLPA Steps

A

denaturation
Probe hybridization
Ligation
PCR
Capillary electrophoresis
analysis

24
Q

when does chromatin modification happen?

A

before transcription

25
Q

which part of histones are available for chemical modification

A

histone tails (protrude outwards)

26
Q

______________ of histone tails promotes loose chromatin structure that permits transcription

A

acetylation
- when nucleosomes highly acetylated = chromatin less compact = DNA accessible for transcription

27
Q

Euchromatin

A

less condensed form of eukaryotic chromatin = available for transcription

28
Q

this agent arrests cells at metaphase

A

colcemid

29
Q

describe steps in Giemsa staining

A
  1. dip slides in trypsin (frees histones and other proteins associated with DNA so Giemsa can stain DNA)
  2. rinse in saline
  3. incubate in Giemsa for ~1min
  4. rinse with tap water
  5. dry using fan
  6. view with light microscope

longer dry = sharper bands

30
Q

the most common method for staining chromosomes

A

Geimsa staining

31
Q

G-banding

A
  • Giemsa for chromosomes
  • lighter areas = euchromatin
  • dark regions = heterochromatin
  • centromeres do NOT stain
32
Q

What is G-banding used for

A

to identify chromosome abnormality and rearrangements in genetic diseases and cancers

33
Q

T or F. in G-banding, resolution is related to sensitivity

A

T
degree of resolution also varies depending on mitotic stage

34
Q

karyotype

A

an individual’s complete set of chromosomes
ex: 46,XX

35
Q

aneuploidies

A

abnormal # of chromosmes
most not ocmpatible w life

36
Q

balanced translocation

A

usually compatible w life; ppl dont even know they have it
chromosomes sometimes don’t line up easily; can be reciprocal or one piece attached to the other
at least one good copy of each gene so not detrimental

ex: chr 13 broke off and attached to chr 5

37
Q

unbalanced translocation

A

translocation between chromosomes resulting in gain or loss of genetic material, likely resulting in a chromosomal condition
- usually occurs when balanced traslocation person has children

38
Q

isochrome

A

unbalanced structural abnormality
- two p arms or two q arms separate together
- there’s both a loss and a gain of genetic material

39
Q

what is FISH

A

deploys DNA probes specific for each chromosome (or subchromosomal region or single locus)
- probes fragments of DNA or RN = usually 100-1000bp
- used to detect presence of nucleotide sequences that are complementary to sequence in the probe
- probes are labeled with modified nucleotides that fluoresce under particular conditions
- by using different fluorochromes, a karyotype can be “painted” as desired

40
Q

FISH whole chromosome probes

A

collections of smaller probes, each of which binds to a different sequence along length of a given chromosome

41
Q

spectral karyotyping

A

FISH
- can label each chromosome a different colour
- VERY expensive so not used routinely
= 24 chromosme-specific painting probes are used i just one FISH experiment

42
Q

FISH centromeric probes

A
  • can be used on interphase and metaphase chromosomes
  • used to enumerate chromosomes
  • typically used as controls
43
Q

locus specific FISH probes

A

bind to a particular region of a chromosome
- useful when scientists have isolaed a small portion of a gene and want to determine on which chromosome the gene is located or how many copies of a gene exists within a particular genome
> CNV probe, fusion probe, break-apart probe

44
Q

G BANDING VS FISH

A

G-banding = large changes in chromosome

FISH = small changes not visible by G-banding or if we want fast results

45
Q

CNV probes

A

designed to hybridize to a precise gene location
identify gene deletions and amplifications

46
Q

gene fusion probes

A

occur when two normally separated genes are joined

while normal cell will display the colours as separate signals, a cell that has fusion will show the signals less than one signal width apart

47
Q

break apart probes

A

a single probe w 2 fluorophores

probe target twoareas of a specific gene sequence

when intact= yellow

when apart = red and green seen

MLSCI 480 (16 decks)

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