SECTION A: MULTIPLE CHOICE SECTION
1.
2.
3.
4.
5.
C
A
D
A
C
6.
7.
8.
9.
10.
A
D
C
C
B
11. D
12. A
13. C or D
14. E
15. C
SECTION B: SHORT ANSWER SECTION
1. Paired statements needed for differences
(a) mitosis and meiosis
Mitosis
(2)
Meiosis
 type of cell division
 starts w one body cell with 46 chroms
Similarity
starts with a body cell
results in 2 daughter cells
results in cells w 46 chroms
results in cells identical to
Difference
parent
 involves one phase




 starts with a body cell in the
testes/ovaries specifically
 results in 4 daughter cells
 results in cells w 23 chroms
 results in cells non-identical to
parent
 involves two phases
 daughter cells are smaller than
parent cell
(b) DNA and RNA
(2)
DNA
Similarity

Difference 


RNA
 nucleic acid
 found in nucleus
 composed of nucleotides
 nucleotides contain sugar, phosphate group & nitrogen bases
found in nucleus only
 found in nucleus & cytoplasm
involved in transcription only
 involved in transcription &
sugar = deoxyribose
translation
bases = A, C, T and G
 sugar = ribose
 bases = A, C, U and G
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(c) Transcription and Translation
Transcription
Translation
 both involved in protein synthesis
 both involve RNA
 both require enzymes
Similarity

Difference 



(2)
occurs in nucleus
requires DNA
produces mRNA
does not require ribosomes
does not require tRNA





occurs in cytoplasm
does not require DNA
produces polypeptides
requires ribosomes
requires tRNA
(Total = 6 marks)
2.
a. Somatic.
Cells are in pairs and gametes do not have homologous pairs of chromosomes.
(2)
b. 0.5 mark for each correct answer; 0.5 mark for each reason
i. Domestic fowl b/c have a range of chrom sizes & a similar number
(1)
ii. Fruit fly b/c have a very low no of chroms compared to humans
(1)
(Total = 4 marks)
3.
Template Strand of DNA
A T G G G C C T G T G G T A G
When this strand of DNA is transcribed, the resulting mRNA sequence is:
A U G - G G C - C U G - U G G - U A G
When this mRNA sequence is translated, the resulting amino acid sequence is:
Met - Gly - Leu - Trp - Stop
(Total = 2 marks)
2
4.
M1 = correctly labelled base, sugar & phosphate
M2 = structure; phosphate and base shown linked to correct carbon atoms on sugar;
M3 = covalent bond(s) labelled between sugar and phosphate / between sugar and base;
M4 = base options and sugar options identified.
(Total = 4 marks)
5.
(a) inheritance of genes located on the autosomes (chroms 1-22)
(1)
(b) no gender bias of M:F
affected son from affected father
(2)
(c) A=ACHOO syndrome; a = unaffected
Individual II–1 = AA or Aa
+ working
(2)
(d) Individual III–4 = aa
+ working
.
(2)
(Total = 7 marks)
6.
(a) Identify the type of inheritance described by this relationship.
0.5 mark - Complete dominance or recessive inheritance
0.5 mark - Autosomal inheritance
(1)
(b)
error in marks  (2)
A and B alleles are both dominant over O
Parents: AO x BO
Possible phenotypes of offspring: 25% A : 25% B : 25% AB : 25% O
(c)
No. Could only be A, B or O
They are homozygous O – so they will only ever be able to contribute an O allele
(3)
(Total = 6 marks)
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7. Outline the evidence provided by DNA for the common ancestry of living organisms.
DNA/genetic code is universal;
same structure of double helix of complementary strands;
same base pairing rule - always pairing of AT and GC;
small differences in DNA show closer relationships;
identified through DNA hybridisation
humans have the same biochemistry as all organisms so part of same evolution/common
ancestry;
(Total = 3 marks)
8. Outline the evidence for evolution provided by homologous structures.
comparative anatomy of groups of animals or plants shows certain structural features are
basically similar;
homologous structures are those that are similar in shape in different types of organisms;
structural similarities imply a common ancestry;
(homologous structures) used in different ways;
example is pentadactyl limb in vertebrates / modification of ovary wall or pericarp to
aid seed dispersal / other suitable example;
adapted to different mode of locomotion in particular environment /
example of two differences such as bat’s wing and human hand;
illustrates divergent evolution since basic plan adapted to different niches;
the more exclusive the shared homologies the closer two organisms are related;
certain homologous structures in some species with no apparent function such as
human appendix (homologous with functional appendix in herbivores);
(Total = 3 marks)
9. Explain how natural selection leads to evolution.
parents produce more offspring than required to keep numbers constant;
more are produced than the environment can support;
example of an environmental condition;
these offspring show variation;
some are better adapted than others to the environment;
these tend to survive to breed themselves;
characteristics are inheritable;
so the new generation has these characters too;
this leads to changes in the population as a whole;
these changes constitute evolution;
(Total = 5 marks)
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