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Advanced Mol Cell > Chromosomes > Flashcards

Chromosomes Flashcards

1
Q

LO:
Understand how DNA is packaged into chromatin and describe the structure and function of histones.

Understand that chromosome structure changes at different phases of the cell cycle.

Understand the structure-function relationships of telomeres, centromeres, replication origins and kinetochores.

Understand that non-protein-coding DNA exists in the genome and be able to describe characteristics of repeated DNA elements.

Describe the different types of eukaryotic transposable elements and their replication and transposition mechanisms.

A

1

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2
Q

SIMPLY- what does packing DNA into chromatin fibres enable?

A

SELECTIVE gene expression
replication and transmission of the genome to progeny cells

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3
Q

Each chromosome pair differs in …. and DNA ……..

A

size and sequence

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4
Q

From interphase nuclei, and beyond, how do individual chromosomes occupy the nucleus

A

with distinct subnuclear territories (google what this means)

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5
Q

what is a chromosome in terms of chromatin formation

A

highly coiled fibre of chromatin

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6
Q

using EM, interphase chromatin resembles ‘beads on a string’- what are the beads called

A

nucleosomes

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7
Q

how many histone complexes will make up a nucleosome

A

~ 8 histones per nucleosome

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8
Q

what do the N-terminals from the histones interact with? and what do these interaction facilitate?

A
  1. free to interact with other proteins
  2. facilitates REGULATION of chromatin STRUCTURE and FUNCTION.
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9
Q

Name of the linker histone that straps DNA onto histone octamers?

A

H1

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10
Q

what do the H1 or linker histones do to DNA thats attached?

A

limits movement relative to the H1 module

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11
Q

what is the result of the H1 histone complex on transcription?

A

general repressor o transcription

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12
Q

what is the size of the chromatin scaffold

A

30nm

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13
Q

definition of chromatin

A

DNA and proteins packaged together

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14
Q

simply what are fractal globules

A
  1. globules within globules
  2. they can reversibly condense and decondense without becoming knotted
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15
Q

specialised DNA sequences in chromosomes facilitate….
1. simple
2. harder- duplicated parts

A
  1. reliable and complete replication
  2. segregation of duplicated chromosomes during division
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16
Q

definition of telomeres

A

specialised repetitive DNA sequences at chromosome ends

17
Q

what are telomeres replicated by
1- simple
2- name of it

A
  1. specialised DNA polymerase
  2. called Telomerase
18
Q

Part I
role of Alpha-satellite DNA in cell division
-centromeres

A
  1. centromeres contain A-S DNA repeats, readily form condensed chromatin
19
Q

Part II
Kinetochore, inner and outer plate
inner plate binds to ..
outer plate binds to…

A
  1. inner plate proteins bind to chromatin containing A-S DNA
  2. Outer plate proteins bind to components of mitotic spindle- i.e microtubules
20
Q

In yeast-
what does the kinetochore link a single nucleosome of CENTROMERIC chromatin to?

A

a single microtubule

21
Q

what are transposons and what do they do?

A

they are mobile genetic elements that ‘jump’ around the genome
- transposable elements

22
Q

3 different types of transposons?
1. simple
2. viral
3. PolyA

A
  1. DNA transposons
  2. Retroviral Transposons
  3. Non-retroviral PolyA transposons
23
Q

how do DNA transposons ‘jump’

A

move by a cut-and-paste mechanism w/o self-duplication
req- transposon-encoded enzyme TRANSPOSASE

24
Q

do it
Finnegan DJ (2012) Curr. Biol. 22: R432-R437.

A

now

25
Q

replication of other transposable elements- like retrotransposons

A

-using RNA intermediates- producing new DNA copies
-They integrate at new genomic locations
-USING self-encoded Reverse transcriptase

26
Q

examples of retrotransposons
TY
TY
EVR

A

Ty1-copia
Ty3-gypsy
ERV elements

27
Q

what do retrotransposons not fully encode

A

they don’t fully encode ACTIVE infectious viruses

28
Q

sequence of replicating ‘other transposable elements’ (5)
(1. RNA and cell, 2. self-encode role, 3. new DNA, 4/ 5. leading to protein gain

A
  1. Entry of RNA intermediate into the cell-> loss of the envelope
  2. Self encoded reverse transcriptase makes RNA-> RNA/ DNA-> DNA/ DNA double helix
  3. copy of the DNA integrated into host chromosome
  4. transcription- many RNA copies
  5. Translation= making specific proteins for new cells-
    capsid protein, Envelope protein, Reverse transcriptase
29
Q

Non-retroviral

A

PolyA retrotransposons- abundant in vertebrates

30
Q

integrated PolyA transposon -L1 element- what is the next stage 1,2,3,4

A

L1 RNA synthesis- obtain a strand of L1 RNA

31
Q

SUMMARY- simple
effectiveness of chromatin and nucleosomes

A
  1. reversible unfolding and compaction- allowing gene transcription and DNA rep
    Package DNA into small volume of nucleus, allow faithful segregation of genome for daughters
32
Q

SUMMARY 2- SIMPLE
telomeres
centromeres

A
  1. prevent the loss of DNA sequences from chromosomal ends
  2. mediate chromosome attachment to the mitotic spindle via kinetochore
33
Q

SUMMARY 3- simple
Transposable elements

A

-Genomes of more complex organisms also have huge numbers of repeated DNA sequence elements
CCCAAAGGG etc

34
Q

SUMMARY 4-
DNA transposons, retroviral transposons, and polyA retrotransposons

A

all are mobile genetic transposable elements- repeated sequences- defective versions
make up over half of the human genome

Advanced Mol Cell (11 decks)

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