topic 2.1.3: nucleotides and nucleic acids

Question 1

what is the difference between a pyrimidine and a purine?

Answer 1

purines have a double ring structure (A+G) while pyrimidines have a single ring structure (C+T)

Question 2

describe the process of transcription

Answer 2

1) RNA polymerase attaches to gene
2) helicase breaks H bonds
3) RNA P moves along and lines up RNA nucleotide
4) mRNA strand formed
5) H bonds reform
6) RNA P reaches STOP codon
7) mRNA attaches to ribosome

Question 3

describe the process of translation

Answer 3

1) tRNA mols carry aminos to ribosome
2) tRNA with complementary anticodon attaches
3) another amino brought
4) rRNA catalyses peptide bond between aminos
5) tRNA released, new amino brought

Question 4

what is the role of mRNA?

Answer 4

delivers genetic info from DNA to ribosome

Question 5

what is the role of tRNA?

Answer 5

brings correct aminos to codon on mRNA

Question 6

what is the role of rRNA?

Answer 6

helps translate info in mRNA into protein

Question 7

describe the process of synthesising polynucleotides

Answer 7

phosphate group + sugar group form covalent phosphodiester bond

Question 8

describe the process of DNA replication

Answer 8

1) DNA helicase breaks H bonds between bases to unzip helix
2) each strand is a template for free nucleotides to attach to
3) DNA polymerase joins free nucleotides via condensation reactions in 5’ to 3’ direction
4) H bonds between pairs

Question 9

what is the role of helicase?

Answer 9

breaks H bonds between DNA bases

Question 10

what is the role of polymerase?

Answer 10

catalyses addition of free nucleotides