Unit 1: Extended Response Questions!

Question 1

Describe DNA under the following headings.
(i) Structure of DNA
(ii) Replication of DNA
[9 marks]

Answer 1

(i) Mention:
Double strand of nucleotides/
double helix. [1]
Deoxyribose sugar, phosphate
and base. [1]
Sugar-phosphate backbone. [1]
Complementary bases pair or
A-T and C-G. [1]
Hydrogen bonds between bases. [1]
Antiparallel structure. [1]
Deoxyribose and phosphate at 3´
and 5´ends. [1]
MAX 5 MARKS

(ii) Mention… (and specifically remember):
DNA unwinds. [1]
Hydrogen bonds between strands
break. [1]
Primer needed to start
replication [1]
DNA polymerase adds
nucleotides to 3´end of
primer/3´ (deoxyribose) end
of strand. [1]
One strand replicated
continuously, the other in
fragments. [1]
Fragments joined by ligase. [1]
MAX 4 MARKS

*Can also add diagrams if you get sick of writing. :)

Question 2

Write notes on gene expression in eukaryotes under the following headings:
(i) production of mRNA; 5
(ii) translation of mRNA. 4
[9 marks]

Answer 2

(i)

Question 3

Write notes on stem cells under the following headings:
(i) differentiation of stem cells; 7
(ii) research into stem cells and their therapeutic value. 3
[10 marks]

Answer 3

(i)

Question 4

Give an account of stem cells, their therapeutic use and the ethical issues surrounding their use.
[8 marks]

Question 5

Write notes on mutation under the following headings:
(i) single gene mutations; 4
(ii) chromosome mutations and polyploidy. 5
[9 marks]

Answer 5

(i)

Question 6

Describe the evolution of new species under the following headings.
(i) Isolation and mutation
(ii) Selection
[9 marks]

Answer 6

(i) Mention:
Isolation barriers prevent gene
flow between populations/
populations interbreeding. [1]
Geographical isolation leads to
allopatric speciation. [1]
Behavioural isolation leads to
sympatric speciation. [1]
Ecological isolation leads to
sympatric speciation. [1]
Different mutations occur on
each side of isolation barrier. [1]
Some mutations may be
favourable/provide selective
advantage. [1]
MAX 4 MARKS

(ii) Mention:
Natural selection is the non-random
increase in the frequency of genetic
sequences that increase survival. [1]
There are different selection
pressures each side of the
barrier. [1]
Any 2 from disruptive/
directional/stabilising selection. [1]
Third type of selection from 9. [1]
*Basically name/describe all types of selection.
After many generations/long
periods of time. [1]
New species form.
If populations can no longer
interbreed to produce fertile
young then different species.
MAX 5 MARKS

*Can also diagrams if you get sick of writing. :)

Question 7

Write notes on evolution under the following headings:
(i) natural selection; 5
(ii) genetic drift. 3
[8 marks]

Answer 7

(i)

Question 8

Give an account of genomics and its importance in phylogenetics and personalised medicine.
[8 marks]