| Date | November 2015 | Marks available | 2 | Reference code | 15N.2.HL.TZ0.4 |
| Level | Higher level | Paper | Paper 2 | Time zone | TZ0 |
| Command term | Compare | Question number | 4 | Adapted from | N/A |
Question
In the pea plant (Pisum sativum), the allele for tall plants is A and the allele for short plants is a. The allele for green plants is B and the allele for yellow plants is b.
Determine the phenotype of Aabb.
Compare the information that could be deduced when the genotypes are presented as AaBb or
Deduce one possible recombinant offspring of individual after a test cross.
Markscheme
tall and yellow
Examiners report
Nearly all candidates successfully determined the phenotype.
Answers were variable, with some excellent ones that distinguished between linked and unlinked genes, their position on the same or different chromosomes and the implications for recombination.
About half of candidates knew that the double recessive parent in a test cross would contribute a chromosome with the alleles ab and that recombinants would have new combinations of genes on their other chromosome, either Ab or aB.
