Protein Synthesis

Question 1

State 3 differences b/w the structures of DNA & RNA (3)

Answer 1

1 - DNA is double stranded
RNA is single stranded

2 - DNA has thymine
RNA has uracil

3 - DNA has deoxyribose
RNA has ribose

Question 2

State what is meant by: template for the synthesis of messenger RNA (1)

Answer 2

RNA nucleotides attach to this strand

Question 3

Describe 3 differences b/w the process of replication & transcription of DNA (3)

Answer 3

1 - replication uses DNA nucleotides
transcription uses RNA nucleotides

2 - replication uses DNA polymerase
transcription uses RNA polymerase

3 - replication makes double helix DNA
transcription makes single strand mRNA

Question 4

Describe the structure of a mono-nucleotide found in RNA (2)

Answer 4

• contains ribose, phosphate & nitrogenous base

Question 5

Describe the process of translation (5)

Answer 5

1) mRNA binds to ribosome

2) RNA reads codons & moves along

3) tRNA brings the anti-codon & corresponding amino acids (these form peptide bonds)

4) tRNA detaches to bring another A.A

5) once stop codon reached, no further A.A brought

Question 6

Explain the nature of the genetic code (2)

Answer 6

genetic code = non-overlapping , universal & degenerate

Question 7

Explain: triplet code (2)

Answer 7

• each amino acid coded for by 3 bases
• 12 bases code for 4 amino acids

Question 8

Explain: non-overlapping (2)

Answer 8

• each triplet is discrete
• AAT + AAC + CAG + TTT gives 4 distinct triplets

Question 9

Explain: Degenerate (2)

Answer 9

• more than 1 code can be used for a particular amino acid
• AAT & AAC code for leucine

Question 10

Describe the role of mRNA in protein synthesis (2)

Answer 10

• used in translation
• binds to ribosome

Question 11

Describe the role of tRNA in protein synthesis (2)

Answer 11

• attaches to specific amino acids
• 2 tRNAs bring amino acids together

Question 12

Describe transcription (4)

Answer 12

• DNA helicase breaks hydrogen bonds in DNA, separating strands & exposing nucleotides
• RNA polymerase attaches to exposed DNA strand
• complimentary base pairing b/w DNA and nucleotides
• mRNA detaches

Question 13

Explain the function of the codons at each end of a strand of mRNA (2)

Answer 13

• start codon needed to begin protein synthesis
• stop codon needed to end protein synthesis

Question 14

Explain the term: gene mutation (2)

Answer 14

• change in DNA
• due to change of bases/nucleotides