O-LevelBiologyGenetics & Variation5090/21 · Oct/Nov 2023 · Q69 Marks

Fig. 6.1 shows a biological molecule. [Figure 6.1]

(a)(i)Name this molecule.[1]
(a)(ii)Describe three features of the structure of this molecule.[3]
(b)Animal and bacterial cells contain this molecule. Describe how the location and shape of the molecule differ in animal and bacterial cells. location shape[2]
(c)Explain how this molecule controls cell function.[3]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

[1] 6(a)(i) DNA / deoxyribonucleic acid ;
[3] 6(a)(ii) any three from: two/double strands ; double helix ; made of nucleotides ; strands held together by bonds between the bases ; complementary bases / A – T and C – G ; made from elements C, H, O, N, P ; A sugar phosphate backbone
[2] 6(b) in nucleus in animal cells + in cytoplasm in bacterial cells ; linear/straight / ribbon / strand / AW in animal cells + circular in bacterial cells;
[3] 6(c) any three from: contains genes ; codes / controls for proteins / polypeptides; by the order of bases / nucleotides ; example of protein e.g. enzyme / haemoglobin / antibody ;

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