Genes

Question 1

What is the 5’ and 3’ end of the chain

Answer 1

5’ is the start
3’ is the end

Question 2

What are the classes of RNA

Answer 2

mRNA - encodes different proteins
tRNA - adaptor molecules
rRNA - component of ribosomes

Question 3

What is DNA polymerase III

Answer 3

Major replication enzyme

Question 4

What direction does DNA polymerase synthesise from

Answer 4

Only makes DNA from 5’ to 3’ direction

Question 5

Which strand is replicated discontinuously

Answer 5

The lagging strand as it’s replicated ‘backwards’

Question 6

What is formed by the lagging strand

Answer 6

Okazaki fragments are formed but then sealed by DNA ligaments to then form a continuous strand form

Question 7

What is the use of helicase

Answer 7

Enzyme used to unwind the two strands

Question 8

What are the single -stranded binding proteins (ssBPs)

Answer 8

Used to protect single stranded regions

Question 9

What is the us of topoisomerase

Answer 9

Relieves overwinding

Question 10

How are replication errors avoided

Answer 10

3’ 5’ exonuclease ‘proof reading’ activity and will remove wrong nucleotide from chain

Question 11

What are some mutations from DNA replication errors

Answer 11

-cancer
-genetic disease

Question 12

What is mRNA

Answer 12

Carries genetic information from DNA to ribosome and is transcribed during the transcription process
Tyrosine => uracil (U)

Question 13

What is the site of strand synthesis

Answer 13

The replication fork

Question 14

What is DNA polymerase

Answer 14

Enzyme that catalyses the attachment of nucleotides to the growing strand at replication fork so synthesis only proceeds from 5’ to 3’ end

Question 15

Why does DNA synthesis require initial activity of RNA polymerase (primase)

Answer 15

As it synthesises short RNA primer and DNA polymerase can extend the primer. (As DNA polymerase can only extend an existing strand) RNA primer then later removed from new DNA strand

Question 16

What are types of point mutations

Answer 16

-substitution mutation where one base exchanged for different base
-insertion of extra bases
-deletion of one or more bases

Question 17

What are the steps of RNA maturation

Answer 17

1. Capping - 5’ end is modified by adding a cap and protects RNA from degradation
2. polydenylation - 3’ end modified by adding poly(A) tail - helps with mRNA stability
3. Splicing - removing introns and joining the coding regions exons by spliceosomes to produce mature RNA
4. RNA degradation

Question 18

What is RNA degradation

Answer 18

Poly (A) tail is shortened and allows an enzyme to cut the cap and RNA then degraded by ribonucleases

Question 19

What is the promoter region

Answer 19

Contains start signal sequences and helps to initiate process of transcription

Question 20

What is the termination region

Answer 20

Terminator region contains stop signal sequence

Question 21

What are the dedicated stop codons

Answer 21

-UAA
-UAG
-UGA

Question 22

What are the effects of insertion/deletion mutations

Answer 22

Frameshift mutation - shift in open reading frame => different sequence of nucleotide => protein that doesn’t function properly

Question 23

What is tRNA (transfer)

Answer 23

Carries amino acids to ribosome on the 3’ end and amino acid attached via ester bond

Question 24

What is the elongation cycle

Answer 24

Step in protein synthesis in translation involves addition of amino acids to polypeptide chain on ribosome

Question 25

What is southern blotting

Answer 25

Separating fragments of DNA by gel electrophoresis then transferring them to a membrane and identifying specific DNA sequences using a probe.