Biology · May / June 2021 · Paper 42 · Question 5
0610
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Fig. 5.1 shows some of the stages in the reproduction of the bacterium Escherichia coli. loop of DNA original bacterial cell bacterial cell expands to a critical length and a copy of DNA is synthesised daughter cells are formed daughter cells grow Fig. 5.1
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5(a)[3]
helix ;
one / the same / equal / identical / maintained / constant ;
identical ;
5(b)(i)[2]
0.003 (mm) ;;
5(b)(ii)[2]
any two from:
there are some (before division) cells that are less than 6 µm ; the smallest that divide are 4.5±1 µm in length ;
some cells are less than 3 µm after division (assuming equal division) ;
5(c)(i)[2]
any two from:
(cut using) restriction enzyme ;
to form sticky ends ;
plasmid cut with same enzyme (as new gene) ;
to form complementary (sticky) ends ;
5(c)(ii)[2]
any two from:
rapid rate of reproduction ;
no ethical considerations ;
share same genetic code as other organisms ;
ability to make complex molecules ;
AVP ; do not take up much space / cheap to maintain cultures
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