O-LevelBiologyGenetics & Variation5090/22 · May/June 2023 · Q710 Marks
DNA carries genetic information in the form of genes.
- (a)The paragraph below describes the structure of a DNA molecule. Complete the paragraph by writing the most appropriate word or letter in each space. DNA contains the chemical elements carbon, hydrogen, oxygen, __________ and __________. Two strands of DNA coil together to form a double __________. Each strand is made up of a chain of __________. Bonds between pairs of bases hold the strands together. These bases always pair up in the same way: T with __________ and __________ with __________.[5]
- (b)Explain how genetic modification can be used to change the function of an enzyme so that it acts on a different substrate.[5]
Mark scheme
Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.
- [5] nitrogen; phosphorus ; helix; nucleotides; A + G + C;
- [5] 1 genetic modification + is a change in genetic material AW ; 2 enzymes are proteins; 3 gene codes for protein / enzyme ; 4 change / new + sequence of bases ; 5 change / new + sequences of amino acids ; 6 change / new + shape of enzyme molecule / active site ; 7 active site; 8 complementary shape / fits + to (new) substrate ;
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