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Molecular Biology > Lecture 8 DNA Packaging > Flashcards

Lecture 8 DNA Packaging Flashcards

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1
Q

How big is the human genome

A

3200 mb of DNA in a haploid cell.

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2
Q

How is the human genome organized

A

It is split into 24 linear DNA molecules.

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3
Q

What is Chromatin

A

It is a DNA Protein complex. The proteins are spaced along regular intervals along the DNA.

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4
Q

How was the structure of Chromatin deduced

A

Using endonuclease digestion to digest the Chromatin.

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5
Q

What is the name used to describe the structure of Chromatin

A

Beads on a string structure.

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6
Q

What are the names of the proteins in Chromatin

A

Histone proteins

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7
Q

Give the name of 5 Histones mentioned in lecture slides

A 
H1
H2A
H2B
H3
H4
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8
Q

Is H1 a histone or a family of histones

A

H1 is a family of histones, and includes H1 a - e, H1t and H5

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9
Q

Which histones are in the H1 family

A
  • H1a - e
  • H1
  • H1t
  • H5
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10
Q

In the beads on string structure, which structure is represented by the beads

A

Nucleosomes

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11
Q

What is a nucleosome

A

(The beads on the string)
Each nucleosome is an octamer of 8 proteins.
It contains 2 each of histones H2A, H2B, H3, H4.

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12
Q

What is the role of histone H1

A
  • It is the linker histone

- It attaches outside the nucleosome.

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13
Q

Describe the structure of a chromatosome

A

A chromatosome describes the combination of the nucleosome, plus DNA plus linker histone.

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14
Q

Explain the difference between the nucleosome and the chromatosome

A

Nucleosome simply refers to the octameric protein of 8 histones. The chromatasome refers to the nucleosome plus DNA plus linker histone plus.

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15
Q

Describe the role of Histone H1

A

Histone h1 is the linker histone

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16
Q

What is the effect of the beads on a string level of packaging on the length of DNA

A

Beads on string reduces DNA length to 1/6th of its total length.

17
Q

Describe the order of packaging

A
  • Beads on a string

- 30nm chromatin fiber

18
Q

What is the effect of the 30nm chromatin fibre on the overall length of the DNA

A

Reduces the overall length of the DNA to by a futher 1/7th.

19
Q

How long is the length of the DNA molecule in chromosome 8

A

4.9cm

20
Q

What is the effect of the 30nm chromatin fiber on DNA length in chromosome 8

A

4.9cm is reduced to 1.2 mm

21
Q

What is the highest level of DNA packaging currently known

A

The metaphase chromosome.

22
Q

Where is the metaphase chromosome found

A

Only in dividing cells

23
Q

What is Euchromatin

A

transcriptionally active chromatin, it appears light under microscope. It contains active genes

24
Q

What is heterochromatin

A

transcriptionally inactive chromatin, supercoiled, it appears dark, and on the edges of the nucleus. Contains inactive genes.

25
Q

What are the two types of heterochromatin

A
  • Constitutive heterochromatin

- Facultative heterochromatin

26
Q

What is constitutive heterochromatin

A

it contains DNA that is always tightly packed in every single cell

27
Q

What is facultative heterochromatin

A

It contains DNA that is tightly packed only in some cells

28
Q

What is the role of the nucleolus

A

Nucleolus contains ribosomal RNA genes and is the site of ribosome biogenesis . ribosome production.

29
Q

Describe the state/levels of packaging of DNA in Euchromatin

A
  • DNA in form of 30 nm chromaitn fibre

- attached to the nuclear matrix and nuclear lamina.

30
Q

Why is Euchromatin DNA attached to the nuclear lamina and nuclear matrix

A

So that it does not get tangled up.

31
Q

List the names of some nuclear matrix and nuclear lamina associated diseases

A
  • Progeria
  • Downs’ syndrome
  • Huntingtons disease
32
Q

Describe the role of the centromere in the metaphase chromosome

A

Centromere holds the daughter chromsomes together, and it contains special histones - CENP-A instead of H3.

33
Q

Describe the role of the telomeres in metaphase chromosome

A

Telomeres protect the ends

  • from exonuclease attack
  • from being mistaken for chromosome breaks and joined together.
34
Q

Telomeres protect chromosomes from

A
  • From exonuclease attack

- from being mistaken for chromosome breaks and joined together.

Molecular Biology (19 decks)

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