Genetics

Question 1

DNA

Answer 1

Acts as a store for genetic info
A-T and C-G, hydrogen bonded
Sugar - Deoxyribose
Phosphate backbone
Double stranded

Question 2

RNA

Answer 2

Translation of DNA to proteins
Uracil instead of thymine

Question 3

DNA replication

Answer 3

Separate strands with helicase
DNA polymerase binds to the primer and makes the new strand of DNA in the 5’ to 3’ direction
Exonuclease removes all the RNA primers from both strands of DNA
Another DNA polymerase fills the gaps
Ligase seals up the fragments of DNA in both strands to form a continuous double strand

Question 4

Triplets and Proteins

Answer 4

Triplet is a code for a specific amino acid
Proteins are made from a sequence of amino acids

Question 5

Organisation of the Human Genome

Answer 5

Roughly 30,000 genes in the human genome
The rest of the genome is made up of non-coding RNAs and gene control regions

Question 6

Exons and Introns

Answer 6

Exons are the sections of genes that encode proteins
Introns are removed by splicing during mRNA processing

Question 7

Control of Gene Expression definitions

Answer 7

Promoter - initiation of transcription –> RNA polymerase binds to it
Enhancer - proteins bind to enhance gene expression
Silencer - repressor proteins bind to prevent gene expression
Acetylation allows gene expression to be turned on –> increases transcription
Methylation means gene expression is turned off –> inhibits transcription

Question 8

6 Controls of Gene Expression

Answer 8

1) Transcriptional regulators (turn genes on or off)
2) RNA processing
3) Nuclear export of mRNA
4) Translation
5) mRNA degradation
6) Protein activity

Question 9

Transcription

Answer 9

INITIATION: RNA polymerase separates the 2 DNA strands as it moves along
ELONGATION: RNA polymerase reads bases and uses them to make an mRNA strand - synthesised in the 5’ to 3’ direction
Template strand used to make mRNA strand
TERMINATION: RNA polymerase detaches and DNA closes back into double helix, allowing the mRNA strand to leave the nucleus for a ribosome

Question 10

mRNA modification

Answer 10

5’ Cap: Promotes translation and prevents degradation of mRNA by exonuclease
RNA splicing: Removes introns to only leave the protein coding sequence
Polyadenylation: Makes the mRNA more stable

Question 11

Translation

Answer 11

INITIATION: Ribosome and mRNA bind together
tRNA brings amino acid and tRNA binds to RNA by complementary base pairing
ELONGATION: tRNA brings amino acids in correct order into the A site so ribosome can join them together and build up a chain of amino acids
Amino acids are joined by peptide bonds (P site) and then each tRNA detaches through the E site
TERMINATION: stop codon is reached