3.9 DNA replication/genetic code

Question 1

role of DNA helicase

Answer 1

travels along DNA backbone and catalyses reactions that break hydrogen bonds between bases to unwind and separate the 2 strands

Question 2

role of DNA polymerase

Answer 2

catalyses formation of phosphodiester binds between free nucleotides and newly exposed bases

Question 3

stages of semi-conservative replication

Answer 3

1. helicase causes two strands of DNA to untwist and separate, exposing the bases
2. each strand is used as a template to make 2 new double strands
3. new nucleotides pair to exposed bases
4. DNA polymerase causes each new chain of nucleotides to be bonded together
5. each molecule twists to form double helix

Question 4

when do mutations occur

Answer 4

when sequences of bases aren’t matched exactly

random and spontaneous

Question 5

what is the genetic code

Answer 5

the sequences of bases in DNA are ‘instructions’ for sequences of amino acids in protein production

UNIVERSAL

Question 6

triplet code

Answer 6

code in the base sequences

Question 7

codon

Answer 7

sequence of 3 bases

codes for amino acid

Question 8

what is a gene

Answer 8

section of DNA that contains complete set of bases to code for entire protein

Question 9

why is it a degenerate code

Answer 9

there are 64 different base codons
1 codon = start codon (ensures no overlapping)
3 codons = ‘stop’ codons

amino acids can be coded for by more than one codon