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Molecular Biology > Overview of DNA Replication and Chromosome Structure > Flashcards

Overview of DNA Replication and Chromosome Structure Flashcards

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1
Q

Does DNA replication follow a conservative mechanism or a semiconservative mechanism?

A

SEMICONSERVATIVE MECHANISM

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2
Q

What can be noticed in origins of replication of a genome?

A

They are A - T rich regions, because this base pairing is easier to separate due to its smaller quantity of hydrogen bonds.

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3
Q

What unwinds DNA in DNA replication?

A

HELICASES

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4
Q

What is a primer?

A

Specialized RNA polymerase composed of about 12 nucleotides.

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5
Q

Why is yeast often used in experiments?

A

Because yeast, which is a unicellular organism, is very easy to manipulate it because you can transform it just like a bacteria with a plasmid, yet it is still a eukaryote.

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6
Q

What is replicated first: euchromatin or heterochromatin?

A

EUCHROMATIN, because it is already opened.

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7
Q

During what cell cycle phase does chromatin decondense?

A

INTERPHASE (G1, S, G2)

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8
Q

What are Histones?

A

They are NUCLEAR PROTEINS which have the task of COMPACTING and ORGANIZING chromosomal DNA.

Rich in POSITIVELY CHARGED AMINO ACIDS, which interact with the negatively charged phosphate groups in DNA

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9
Q

What is Chromatin?

A

The COMPLEX OF HISTONES AND DNA.

  • About half DNA and half protein (majorly histones) by mass.
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10
Q

What are centromeres and telomeres?

A

Specialized chromosome regions that contain few genes.

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11
Q

Are centromeres and telomeres Euchromatin or Heterochromatin?

A

HETEROCHROMATIN

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12
Q

What is a Barr Body?

A

It is a highly proteinaceous heterochromatic blob that is the INACTIVATED X CHROMOSOME IN FEMALES.

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13
Q

What can the Barr Body be used for?

A
  • It can be used to test for SUPER MALES and KLINEFELTER’S SYNDROME by buccal smear.
  • It can be used to TEST FOR AUTHENTICITY OF GENDER, which is what they did in the Olympics back in the days.
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14
Q

Who made the discovery of the Barr body?

A

MURRAY BARR

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15
Q

What is the major chromatin protein?

A

HISTONES

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16
Q

In what physiological conditions is chromatin in its fibre form?

A

When it is isolated under physiological ionic conditions (150 mM KCl, 4 mM MgCl2).

17
Q

In what conditions is chromatin in its “string on a bed”/extended form?

A

When it is isolated under low ionic conditions, no Mg2+.

18
Q

What are the “beads” in the “beads on a string” model of chromatin?

A

NUCLEOSOMES

19
Q

What is a Nucleosome made of?

A
  • PROTEIN CORE HISTONE OCTAMER (2 x H2A, 2 x H2B, 2 x H3, 2 x H4)
  • 147 BASE PAIRS OF DNA
20
Q

What is necessary to the formation of a Histone?

A

HAND SHAKE DOMAIN (without it, you die)

21
Q

What are 3 of the PTMs (Post Translational Modifications) of histone tails and what do they do?

A
  • METHYLATION of lysine or arginine (mono, di- or tri-methylation):
    Forms a binding site for CHROMODOMAINS (closes up chromatin / heterochromatin)
  • ACETYLATION of lysine:
    Forms a binding site for BROMODOMAINS (opens up chromatin / euchromatin)
  • PHOSPHORYLATION of serine or threonine
22
Q

How do histone tail modifications affect nucleosome behaviour?

A
  • Modifications can AFFECT THE CHARGE on the histone and its ELECTROSTATIC INTERACTIONS with DNA.
  • Modifications can RECRUIT SPECIFIC PROTEINS that alter nucleosome structure and function
23
Q

What is a Nucleosome?

A

It is the PRIMARY STRUCTURAL UNIT OF CHROMATIN.

24
Q

What are the 2 types of histone tails?

A

N and C TERMINAL TAILS

25
Q

In what type of histones are found the C terminal tails?

A

H2A and H2B

26
Q

What are pre-replicative complexes?

A

A bunch of protein that seed the ability to replicate once they are loaded onto origins of replication, which are A-T rich regions.

27
Q

What can DNA microarrays tell you?

A

It tells you…

  • WHERE origins of replication are located
  • That they are moving BIDIRECTIONALLY
  • How QUICKLY they are doing that overtime.
28
Q

Name one well known bromodomain.

A

TFIID

Molecular Biology (9 decks)

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