DNA

Question 1

How many base pairs are there in a turn of DNA?

Answer 1

10.5

Question 2

What are major and minor grooves?

Answer 2

Where the DNA wrap into a double helix each twist alternates in length due to one side of the base pair bond being longer than the other

Question 3

How is DNA packaged?

Answer 3

DNA wraps twice around 4 histones

Question 4

What are histones?

Answer 4

Positively charged molecules that condense DNA

Question 5

How is bacterial DNA different to eukaryotic DNA?

Answer 5

Its circular

Question 6

How is DNA replication initiated in bacteria?

Answer 6

Begins at 1 unique origin and proceeds bidirectionally, slow

Question 7

How is DNA replication initiated in eukaryotes?

Answer 7

Begins at multiple origins and proceeds bidirectionally, much quicker

Question 8

What is DNA polymerase?

Answer 8

An enzyme that replicates DNA with a primer

Question 9

What unwinds the double helix of DNA?

Answer 9

Helicase

Question 10

What makes the primers?

Answer 10

Primase

Question 11

What direction does DNA replication occur in?

Answer 11

5’ to 3’

Question 12

What is telomerase?

Answer 12

An enzyme that has a bit of DNA with RNA on it that can start making DNA without a primer

Question 13

What is telomerases function?

Answer 13

To allow space for a primer to be added without important DNA being lost
Its activity decreases over time which is why we get old

Question 14

What are the 4 types of DNA repair?

Answer 14

Mismatch repair
Direct repair
Excision
Nonhomologous end joining

Question 15

What are the 3 stages of gene expression?

Answer 15

DNA replication
Translation
Transcription

Question 16

In eukaryotes what does DNA polymerase 1 synthesise?

Answer 16

rRNA

Question 17

In eukaryotes what does DNA polymerase 2 synthesise?

Answer 17

mRNA

Question 18

In eukaryotes what does DNA polymerase 3 synthesise?

Answer 18

tRNA

Question 19

How is mRNA processed after being transcribed?

Answer 19

Spliced to remove the introns

Capped and polyadenylation

Question 20

What is capping and polyadenylation?

Answer 20

Where a 5’ cap is added so the ribosome cane recognise the start of the gene

Question 21

What is alternative splicing of mRNA?

Answer 21

When some adjacent exons are removed to produce multiple proteins from one gene

Question 22

What is a transcription factor?

Answer 22

Regulates transcription

Either activator or repressor of RNA polymerase

Question 23

What are histone tails?

Answer 23

Chains of amino acids that are positively charged so attract the DNA to wrap around them

Question 24

How can histones be modified to bring about post translational modification@

Answer 24

Histone acetylation

Histone deacetylation

Question 25

What is histone acetylation?

Answer 25

transcriptional activation - When acetyl groups are added to the histone tails which neutralises the tails so DNA doesn't wrap around as well

Question 26

What is histone deacetylation?

Answer 26

Transcriptional repression - When acetyl groups are removed from histone tails so its more positive and DNA wraps around more

Question 27

What is epigenetic gene regulation?

Answer 27

When modifications change gene expression without changing the DNA sequence

Question 28

What forms of epigenetic gene regulation are there?

Answer 28

DNA methylation - silences genes Histone modification miRNA related gene silencing

Question 29

What are aminoacyl-tRNA synthetases?

Answer 29

Enzymes that join tRNA and amino acids together

Question 30

What are the 3 active sites of ribosomes?

Answer 30

A site - aminoacyl-tRNA P site - peptidyltransferase E site - exit

Question 31

What is a polyribosome?

Answer 31

One piece of mRNA with lots of ribosomes attached to it all translating at once

Question 32

What are the 3 main checkpoints in the cell cycle?

Answer 32

G1 - before S phase G2 - after S phase Mitosis - before cytokinesis

Question 33

What are cyclins?

Answer 33

Proteins that control the cell cycle

Question 34

How do cyclins control the cell cycle

Answer 34

They have different levels through the cell cycle | Protein kinase is activated by them which allows the cell cycle to occur

Question 35

What is an example of cyclins?

Answer 35

Retinoblastoma (Rb) protein

Question 36

How does Rb protein control the cell cycle?

Answer 36

Binds to the transcription factor that controls the S phase so cycle stops