DNA and Gened And Protein synthesis

Question 1

Explain the difference in the percentage of guanine bases inhje two species of bacterium

Answer 1

Different GENES (1 mark)

A d different BASE sequence (1 mark)

Question 2

Complete Table 2 to show the base sequence of the DNA template from which this mRNAwas transcribed and the encoded amino acid sequence

Answer 2

G binds to C
C binds to G

U Binds to A
T binds to A

So I’d on the base mRNA strand, the nucleotide was U, the base on DNA would be A
And if the base on the mRNA strand is A then the base sequence on the DNA template is T

Question 3

Give two tutors of molecules dorm which A ribosomes is made

Answer 3

ribosomal RNA and polypeptides

Question 4

Describe the role of a ribosome in the production of a polypeptide of a polypeptide. Do not include transcription in your answer (3 marks)

Answer 4

mRNA binds to ribosome

tRNA molecules with complementary anticodon
sequence moves to the ribosome and binds to the anticodon

This catalyses the formation of the peptide bond between the amino acids held together by tRNA

Ribosome moves along mRNA to the next codon

Question 5

Messenger RNA (mRNA) is used during translation to form polypeptide 
Describe how mRNA is produces itbe nucleus of a cell

Answer 5

Helicase (1 marks)

Breaks hydrogen bonds (1 marks)

Only one DNA strand acts as template (1 mark)

RNA nucleotides attracted to expand bases (1 mark)

Attracting according to base pairings rule (1 mark)

RNA polymerase joins (RNA) polypeptide together (1 mark)

Pre mRNA spliced to remove introns (1 mark)

Question 6

Wuggets one advantage of showing the genetic code as base sequences on mRNA rather than triplets on DNA

Answer 6

DNA has two strands each with a different (complementary) base sequence / ribosomes assemble polypeptide using mRNA

Question 7

Suggest the role of the mRNA base triplets UGA, UAG and UAA

Answer 7

Stop translation

Result in detachment of polypeptide chain from ribosome

Question 8

Describe the structure of proteins .(6 marks)

Answer 8

Polymer of amino acids (1 marks)

Joined peptide bonds in an condensation reaction (1 marks)

Primary structure is the order of amino acids (1 mark)

Secondary structure is folding of polypeptide chain due to hydrogen bonding (1 mark)

Tertiary structure is the 3D folding due to hydrogen and ionic and disulfide bonds (1 mark)

Quaternary structure is two or more polypeptide chains ⛓ ( 1 mark)