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Biology > chromosomes + chromatin > Flashcards

chromosomes + chromatin Flashcards

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1
Q

what is a nucleosome

A

DNA bound to central octamer of histone proteins

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2
Q

how many DNA molecules does 1 chromosome have. And how many DNA molecule after replication

A

1 chromosome = 1 DNA molecule
after replication = 2 DNA molecules (sister chromatids)

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3
Q

what do chromasomes fold into

A

compartments: A (open) B(closed).

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4
Q

What are TADS

A

(topologically associated domains) - self interacting genomic region
they are chromatin within the compartments

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5
Q

what are the levels of organisation of a chromosome

A
  1. nucleosome
  2. domain - chromatin domains
  3. territories - TADS form
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6
Q

what controls the chromatin domains

A
  • histone modifications
  • histone varients
  • chromatin assoc proteins
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7
Q

Which histones are in the nucleosome

A

H2A, H2B, H3, H4
H1 differs in species and tissues outside

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8
Q

what do nucleosomes do during transcription

A

they slide down DNA to open it and expose the DNA to allow transcription.
when nucleosomes close together TFs cant bind

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9
Q

Affects of methylation and acetylation on transcription

A

increased methylation - nucleosomes tight so TFs cant bind (ch3 groups block)
increased acetylation - nucleosomes loose packed so Tfs can bind ( acetyl groups cause repulsion)

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10
Q

what are LADS and where is it common in

A

(lamina assoc domains) = parts of chromatin that interact with lamina. has lots of methylated H3 histone
common mod in heterochromatin

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11
Q

what are NADS

A

nucleolar assoc domains

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12
Q

name the architectural proteins (that the DNA loops in TADS are maintained by)

A
  • histones
  • chromatin remodelling enzyme
  • Zinc finger
  • cohesins
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13
Q

what do chromatin remodelling enzymes do

A

promotes euro + heterochromatin

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14
Q

what does zinc finger do

A

mediates DNA looping + regulates transcription
zinc atoms stabilize folds and it is a protein motif

Baso regulates gene organization and expression

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15
Q

what do cohesins do

A

bind sister chromatids together (mitosis)

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16
Q

Def of epigenetics

A

changes in gene expression by chromatin modification without changing DNA seq

17
Q

name some histone modifications

A
  • acetylation
  • methylation
  • phosphorylation
  • deamination
  • ubiquitination
18
Q

What are protamines

A

In sperm head
replace histones late in the haploid phase of spermatogenesis

19
Q

Where is heterochromatin found

A

telomeres and centromeres

20
Q

What is karyotype, karyogram, idiogram

A

Karyotype: number and visual appearance of chromosomes in nucleus

Karyogram: chromsomes in homologous pairs and numbered according to LENGTH AND CENTROMERE POSTION

Idiogram: representation of karyotype as a diagram

21
Q

Types of chromosomes

A

metacentirc
submetacentric
acrocentric
telocentric

22
Q

Group c chromosomes 6-12 are what type and X

A

submetacen tric

23
Q

Group G 21-22 are what type and y

A

acrocentric

24
Q

Group F 19-20 what type

A

metacentric

25
Q

Group A 1-3 what type

A

1 and 3 metacentric 2 submetacentrixc

26
Q

Group B Group D 13-15 what type

A

acrocentric

27
Q

Group B what type 4-5

A

submetacentric

28
Q

Grouo E 16-18

A

16 metacentric but 17 18 submetacentric

29
Q

What is karyotype evolution due to

A

chromosomal aberratiosn

duplicTIONS, DELETIONS inversions= results in loops in meiosis

30
Q

What happens when loops are formed during crossing over

A

Deltions and duplications occur on the gamete chromosomes for example which means fertility reduced

Bc of the iversion eg, crossing over tried to occur at correct place but in order to do so they have to form loops and in the process duplicate or delete dome bases

31
Q

How can karyotype aberrations cause new species

A

If 2 homologous chromosomes have the same defect then fertilty same- homozygous for the defect
RESPRODUCTIVLY ISOLATED

Can carry this onto next geenration

32
Q

What is robersonian translocation

A

fusioon of 2 acrocentric chromosomes - cause extra 21

Can cause down syndrome as inherited from from generations ago

33
Q

Autopolypoploidy and allopolyploidy

A

Auto= all chromosomal set from same species

Allo=Chromosomal sets from close species combines

34
Q

Why are polyplloidies frequent in plants

A

bc asexual repo is very frequent and they have no sex chromsomes

35
Q

Whuch are the chrmosomes in growing oocytes NOT IN MAMMALS

A

Lampbrush chromsomes - prod morphogens

Loops of deciondensed chromsomes

Produce mRNA and non coding rRNA

OOplasmic granules? for segreation

36
Q

What is replication withou cell divisionn

A

ENDOREPLICATION
Causes polyploid cells

eg polytene chromosomes in secretory cells dipteren larvae

Biology (36 decks)

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