DNA & Genomics II

Question 1

What is the start codon(s)?

Answer 1

AUG

Question 2

What is the stop codon(s)?

Answer 2

UAG UAA UGA

Question 3

Which direction is mRNA synthesized?

Answer 3

5’ to 3’ direction

Question 4

Which direction does RNA polymerase move along

Answer 4

3’ to 5’ direction

Question 5

3 types of RNA

Answer 5

Messenger RNA (mRNA), Transport RNA (tRNA), Ribosomal RNA (rRNA)

Question 6

How does tRNA facilitate translation?

Answer 6

It has the ability to bind to specific amino acid and ability of anti-codon to base-pair with mRNA codon.

Question 7

What is the function of rRNA

Answer 7

It associates with a set of proteins to form ribosomes.
It is the main constituents of peptidyl site (P site)and aminoacyl site (A site).

Question 8

Describe the key stages of translation

Answer 8

1. Initiation
2. Elongation
3. Termination

Question 9

Describe elongation process of translation

Answer 9

1. Codon recognition, second tRNA carrying next amino acid binds to A site by complementary base pairing, forming hydrogen bonds between anticodon and second codon on mRNA
2. Peptide bond is formed between amino acids by peptidyl transferase.
3. Ribosome shifts one codon down the mRNA in 5’ to 3’ direction, thus 1st tRNA shifts to E site and released into cytosol and 2nd tRNA, now carrying growing polypeptide and empty A site and is ready to receive 3rd aminoacyl-tRNA

Question 10

Desribe the Amino Acid Activation

Answer 10

Aminoacyl-tRNA synthetase is complementary in conformation and charge to specific amino acid and specific tRNA with specific anticodon. Aminoacyl-tRNA synthetase catalyses the covalent attachment of tRNA to its specific amino acid based on its specific anticodon.

Question 11

What are the 4 types of genetic mutations?

Answer 11

Substitution, Addition, Deletion and Inversion

Question 12

What the outcomes of mutations?

Answer 12

Frame-shift mutation
Silent mutation
Missense mutation
Nonsense mutation

Question 13

Differences between replication and transcription.

Answer 13

Replication : Transcription
DNA polymerase : RNA polymerase
Deoxyribonucleotides dNTP : Ribonucleotides NTP
Both DNA strands are templates : Only 1 DNA strand is template
A->T and G->C : A->U and T->A and G->C
2 dsDNA synthesised as product : 1ssRNA synthesised as product

Question 14

Differences between transcription and translation

Answer 14

Transcription : Translation
Occurs in nucleus of eukaryotes : Ribosomes in cytoplasm at RER
DNA template to mRNA : mRNA to polypeptide
RNA polymerase is enzyme : Peptidyl transferase and aminoacyl tRNA synthetase
Phosphodiester bond between RNA : Peptide bond between amino acids
3’ -> 5’ of DNA template: 5’ -> 3’ of mRNA