SECTION A: MULTIPLE CHOICE SECTION1. C2. A3. D4. A5. C

6. A7. D8. C9. C10. B

11. D12. A

13. C or D14. E15. C

SECTION B: SHORT ANSWER SECTION1. Paired statements needed for differences

(a) mitosis and meiosis (2)Mitosis Meiosis

Similarity type of cell division starts w one body cell with 46 chroms

Difference

starts with a body cell results in 2 daughter cells results in cells w 46 chroms results in cells identical to

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 RNA

Similarity nucleic acid

found in nucleus composed of nucleotides

nucleotides contain sugar, phosphate group & nitrogen bases

Difference

found in nucleus only involved in transcription only sugar = deoxyribose bases = A, C, T and G

found in nucleus & cytoplasm involved in transcription &

translation sugar = ribose bases = A, C, U and G

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(c) Transcription and Translation (2)Transcription Translation

Similarity both involved in protein synthesis

both involve RNA both require enzymes

Difference

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 reasoni. 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 DNAA 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)

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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 = unaffectedIndividual II–1 = AA or Aa + working (2)

(d) Individual III–4 = aa . + working (2)

(2)

(Total = 7 marks)

6. (a) Identify the type of inheritance described by this relationship. (1)0.5 mark - Complete dominance or recessive inheritance0.5 mark - Autosomal inheritance

(b) error in marks (2)A and B alleles are both dominant over OParents: AO x BOPossible phenotypes of offspring: 25% A : 25% B : 25% AB : 25% O

(c) (3)No. Could only be A, B or OThey are homozygous O – so they will only ever be able to contribute an O allele

(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 hybridisationhumans 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 ashuman 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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