genetics past paper questions

Question 1

Answer 1

1. GN and gn linked;
2. GgNn individual produces mainly GN and gn gametes;
3. Crossing over produces some / few Gn and gN gametes;
4. So few(er) Ggnn and ggNn individuals.

Question 2

Answer 2

1.(Individual) 2 has colour vision but 4 is colour blind / 10 has colour vision but 12 is colour blindOR4/12 is colour blind but parents have colour vision;2.So 2/10 must be heterozygous/carriers

;Accept: (1), 2 and 4 or10,(11) and 12.Accept: any suitable description and explanation equivalent to points 1 and 2.Reject: (both) parents heterozygous/carriers.Accept: correct genotypes for 2 and 10.Accept: for 2 marks, if it was dominant the daughters (8 and 10) of individual 4 would be colour blind.

Question 3

Lord Howe Island in the Tasman Sea possesses two species of palm trees which have arisen via sympathetic speciation

The two species diverged from each other after the island was formed 6.5 million years ago

The flowering times of the two species are different

Uing this information suggest how the two species of plan tree arose b sympatric speciation

Answer 3

1. Occurs in the same habitat/environment/population;
2. Mutation/s cause different flowering times;
3. Reproductive separation/isolation OR No gene flow OR Gene pools remain separate;
4. Different allele/s passed on/selected OR Change in frequency of allele/s;
5. Disruptive (natural) selection;
6. Eventually different species cannot (inter)breed to produce fertile offspring;