Exam 1

Question 1

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

Answer 1

• Phospholipids
• Endoplasmic Reticulum

Question 2

This allows passage through the two phospholipid membranes

Answer 2

Nuclear pore complex

Question 3

Provides the structural component to the nuclear envelope

Answer 3

Nuclear lamina

Question 4

Where is heterochromatin located?

Answer 4

On the periphery of the nucleus

Question 5

What must proteins have to enter into the nucleus?

Answer 5

Nuclear Localization Signal (NLS)

Question 6

What is chromatin and where is it located?

Answer 6

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

Question 7

What are histones?

Name all the histones

Answer 7

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

Question 8

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

Answer 8

• 3.2 X 10⁹ base pairs
• 25,000 genes

Question 9

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

What percentage of the genome is made up of exons?

Answer 9

• 27,000 bp
• 10.4 exons
• 1.5%

Question 10

What is a ribosome composed of?

Answer 10

rRNA + proteins (ribonucleoprotein)

Question 11

What takes place at the fibrillar regions of the nucleus?

Answer 11

rDNA is transcribed into rRNA

Question 12

What type of chromosome has stalk and satellite DNA?

Answer 12

Acrocentric chromosomes

Question 13

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

What human chromosomes are acrocentric chromosomes located on?

Answer 13

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

Question 14

Know the checkpoints of the cell cycle

Answer 14

Question 15

T/F: rRNA is translated to protein

Answer 15

False

Question 16

What is the length of helical DNA?

Answer 16

2 nm

Question 17

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

Answer 17

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

Question 18

What is the histone fold?

Answer 18

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

Question 19

What’s the process of histones becoming an octomer?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

Know the step by step process for replication

Answer 21

Question 22

What direction does synthesis occur?

Answer 22

5’ –> 3’

Question 23

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

Answer 23

Leading strand: towards the fork

Lagging strand: away the fork

Question 24

T/F: The leading strand has Okazaki fragments

Answer 24

False: the lagging strand has Okazaki fragments

Question 25

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

Answer 25

Histone chaperones aka chromatin assemnling factors

Question 26

What is Epigenetic inheritance?

Answer 26

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

Question 27

Describe heterochromatin Which areas of the chromosome are rich in heterochromatin?

Answer 27

* Extremely compact DNA, most resistant to transcription * Centromeres and telomeres

Question 28

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

Answer 28

**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

Question 29

Describe the position effect

Answer 29

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

Question 30

What are 4 ways to maintain DNA?

Answer 30

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

Question 31

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

Answer 31

Question 32

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

Answer 32

* **Excision**: wrong nucleotide, add the correct one in * **Break**: Break in phosphodiester backbone

Question 33

What's the difference between a correction and repair?

Answer 33

**Correction**: mistake in DNA replication **Repair**: stimulus that has caused an error like a break

Question 34

Know the difference between base excision and nucleotide excision repair

Answer 34

Question 35

Compare/Contrast dsDNA repair

Answer 35

* 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