3.9 DNA replication and the gene code

Question 1

what is DNA replication (2)

Answer 1

its semi conservation
produces identical copies of DNA molecules

Question 2

outline the steps of semi-conservative DNA repication

Answer 2

Double helix unwinds.
Helicase breaks hydrogen bonds between complementary DNA bases.
Free DNA nucleotides align with exposed bases by complementary base pairing.
Hydrogen bonds reform.
ON LEADING STRAND: (5’ to 3’ direction)

DNA polymerase joins adjacent nucleotides by phosphodiester bonds - continuous.
ON LAGGING STRAND: (3’ to 5’)

Sugar-phosphate backbone forms.
Each DNA molecule has 1 new & 1 old strand - semi-conservative.

Question 3

What enzymes are involved in DNA replication & what are their roles?

Answer 3

HELICASE - breaks hydrogen bonds between complementary DNA bases.
DNA POLYMERASE - forms phosphodiester bonds between adjacent nucleotides.

Question 4

which end does DNA replication start 3 or 5

Answer 4

5’

Question 5

describe the characteristic of genetic code

Answer 5

UNIVERSAL
used by all organisms
DEGENERATE
many codons for 1 amino acid
NON-OVERLAPPING
bases not shared between codons

Question 6

what are introns

Answer 6

Regions of non-coding DNA

Question 7

what are exons

Answer 7

regions of coding DNA

Question 8

what is a mutation

Answer 8

Change in sequence of DNA bases
it may affect phenotype

Question 9

how do mutations arise

Answer 9

random and spontaineously

Question 10

what is a triplet code

Answer 10

Sequence of 3 nucleic acid bases which codes for an amino acid

Question 11

whats a gene

Answer 11

Section of DNA which contains complete sequence of bases to code for a whole protein