Question 20N.2.SL.TZ0.4
| Date | November 2020 | Marks available | [Maximum mark: 8] | Reference code | 20N.2.SL.TZ0.4 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Define, Explain, Sketch | Question number | 4 | Adapted from | N/A |
Sketch the complementary strand to complete the section of a DNA diagram.
[3]
a. correct base sequence: T, G, A;
b. strand drawn anti-parallel;
c. correct shapes used;
Award [2 max] if bonds are not from the correct carbon or if the nucleotides are not joined.
In part (a) most could gain marks for the correct shapes and sequence but did not gain the third mark as it was not shown as antiparallel. Some lost marks as a 2MAX was awarded if the bonds were not from the correct carbons. In part (b) the definition of mutation was quite well known, and most gained some marks in the explanation. Weaker students just wrote about evolution without relating it to mutations as asked. They also tended to give unnecessary examples, involving finches and moths etc.
Define mutation.
[1]
change in genetic makeup/DNA/nucleotide/base sequence
Explain how evolution by natural selection depends on mutations.
[4]
a. mutations cause variation among organisms of same species/population;
b. some variations/mutations make individual more suited to its environment/way of life;
c. individuals that are better adapted survive and produce offspring;
d. individuals pass on genetic characteristics/mutation/variation to offspring;
e. natural selection increases frequency of characteristics/alleles that make individuals better adapted;
