protein synthesis - Topic 2

Question 1

Describe the process of DNA replication

Answer 1

-replication is semi conservative
- DNA Helicase unzips strand of DNA by breaking H bonds
- Free nucleotides in nucleus attach to template strand
- complementary base pairing
- DNA polymerase catalyses the formation of hydrogen bonds between nucleotides
- phosphodiester bonds between bases
- strands run antiparallel

Question 2

Name the features of a nucleotide

Answer 2

Phosphate group
Pentose sugar
Nitrogenous base (ATUCG)

Question 3

Describe the process of transcription

Answer 3

• DNA helicase breaks the hydrogen bonds between between the bases (unzipping)
• gene exposed to be transcribed
• free RNA nucleotides line up with complimentary base pairs and form H bonds with each other
• RNA polymerase forms phosphodiester bonds between the phosphate and pentose sugars to form the sugar-phosphate backbone
• H bonds break between mRNA and DNA strands.
• mRNA strand leaves via nuclear pores

Question 4

Describe the process of translation

Answer 4

(Initiation)
- mRNA attaches to a ribosome
- complementary tRNA anticodons attach the the mRNA codons forming h bonds with each other
(Elongation)
- amino acids on tRNA molecule join through condensation reactions forming peptide bonds
- ribosome catalyses this reaction
(Termination)
-ribosome moves along mRNA molecule synthesising the chain until it reaches a stop codon
- translation stops and polypeptide chain is released

Question 5

State the differences between DNA and RNA

Answer 5

• DNA consists of deoxyribose sugar and RNA consists of ribose
• DNA is double stranded whereas RNA is single stranded
• DNA contains DNA nucleotides (thymine) whereas RNA contains RNA nucleotides (uracil)
• DNA is larger
• both contain phosphodiester bonds between bases

Question 6

What is meant by the term template in the synthesis of mRNA

Answer 6

RNA nucleotides attach to this strand to make a copy for synthesis

Question 7

Differences between Replication and transcription

Answer 7

• R involves DNA T involves RNA
  -R has DNA polymerase whereas T has RNA polymerase
• replication produces identical copies whereas transcription produces a complimentary copy
• R has thymine T has uracil
• R creates a double helix whereas T makes a single strand

Question 8

what is the role of tRNA ?

Answer 8

• carries amino acids to the ribosome
• has an anticodon that is complimentary to a mRNA codon
• each tRNA carries a particular amino acid