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Nuclear Organization and Function > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

The nuclear envelope is made up of two layers of ___ and is continuous with the ___

A
  • Phospholipids
  • Endoplasmic Reticulum
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2
Q

This allows passage through the two phospholipid membranes

A

Nuclear pore complex

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3
Q

Provides the structural component to the nuclear envelope

A

Nuclear lamina

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4
Q

Where is heterochromatin located?

A

On the periphery of the nucleus

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5
Q

What must proteins have to enter into the nucleus?

A

Nuclear Localization Signal (NLS)

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6
Q

What is chromatin and where is it located?

A

Complex of DNA and protein, and is found
in the nucleus of eukaryotic cells

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7
Q

What are histones?

Name all the histones

A
  • Proteins that are responsible for the first level of DNA packing in chromatin
  • H2A (2), H2B (2), H3 (2), H4 (2), and H1 (linker)
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8
Q

How large is the genome in terms of bps and genes?

A
  • 3.2 X 109 base pairs
  • 25,000 genes
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9
Q

What is the average gene size in terms of bps and exons?

What percentage of the genome is made up of exons?

A
  • 27,000 bp
  • 10.4 exons
  • 1.5%
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10
Q

What is a ribosome composed of?

A

rRNA + proteins (ribonucleoprotein)

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11
Q

What takes place at the fibrillar regions of the nucleus?

A

rDNA is transcribed into rRNA

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12
Q

What type of chromosome has stalk and satellite DNA?

A

Acrocentric chromosomes

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13
Q

Where in the nucleus are acrocentric chromosomes located and what do they contain?

What human chromosomes are acrocentric chromosomes located on?

A
  • Fibrillar regions
  • rDNA
  • 13, 14, 15, 21, and 22
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14
Q

Know the checkpoints of the cell cycle

A
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15
Q

T/F: rRNA is translated to protein

A

False

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16
Q

What is the length of helical DNA?

17
Q

How many genes are in a nuclear genome compared to mitochondrial DNA?

A
  • Nuclear genome (>25,000 genes) – linear dsDNA
  • Mitochondrial DNA (~35 genes) – circular dsDNA
18
Q

What is the histone fold?

A

A common motif made up of 3 alpha helices and 2 loops that allows histone dimerization

19
Q

What’s the process of histones becoming an octomer?

A
  1. H3-H4 dimerize –> 2 dimers = tetramer
  2. H3-H4 tetramer –> bind 2 H2AB dimers –> octomer
20
Q

What is the overal process for preventing DNA replication at the origin of replication?

A
  1. Origin recognition complex (ORC) binds to origin of replication
  2. Degradation of phosphate
  3. ORC is phosphorylated to begin replication again
21
Q

Know the step by step process for replication

22
Q

What direction does synthesis occur?

A

5’ –> 3’

23
Q

What direction do the leading and lagging strand grow in relation to the replication fork?

A

Leading strand: towards the fork

Lagging strand: away the fork

24
Q

T/F: The leading strand has Okazaki fragments

A

False: the lagging strand has Okazaki fragments

25
Q

What ensures that newly synthesized daughter DNA is properly packaged into the chromatin?

A

Histone chaperones aka chromatin assemnling factors

26
Q

What is Epigenetic inheritance?

A

Inheritance of chromatin structure, not based on differences in nucleotide sequence of the DNA

27
Q

Describe heterochromatin

Which areas of the chromosome are rich in heterochromatin?

A
  • Extremely compact DNA, most resistant to
    transcription
  • Centromeres and telomeres
28
Q

What is the difference between changes in genetic and epigentic inheritance?

A

Genetic inheritance: gene is turned off due to a change in the DNA sequence. As somatic cells are multiplied and germ cells are produced it remains off

Epigenetic inheritance: gene is turned off due to a change in chromatin structure. As somatic cells are multiplied it remains off but when germ cells are produced it is turned on

29
Q

Describe the position effect

A

When moving heterochromatin near euchromatin it has the potential to silence certain genes.

30
Q

What are 4 ways to maintain DNA?

A
  1. Histone modification - the Histone code
  2. Lysine residues: acetylation, methylation
  3. Serines: phosphorylation
  4. Enzyme modifiers: acetyl transferase, methyl transferase, kinase, phosphatase, ubiquitylation
31
Q

Know the function of the different histone variants. They are inserted based on alternative splicing

32
Q

What’s the difference between an excision and a break?

A
  • Excision: wrong nucleotide, add the correct one in
  • Break: Break in phosphodiester backbone
33
Q

What’s the difference between a correction and repair?

A

Correction: mistake in DNA replication

Repair: stimulus that has caused an error like a break

34
Q

Know the difference between base excision and nucleotide excision repair

35
Q

Compare/Contrast dsDNA repair

A
  • Both repair dsDNA breaks

Nonhomologous end joining: quicker, simple, occurs during G1 or in all somatic cells during mitosis

Homologous recombination: more accurate, occurs during prophase

Nuclear Organization and Function (2 decks)

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