Sex-linked inheritance. Gene interaction
Answers are for parents and teachers.
1
A woman with haemophilia (XʰXʰ) has children with a healthy man (XᴴY). Write the genotypes and phenotypes of the children.
Daughters XᴴXʰ – healthy carriers; sons XʰY – affected.
2
If both parents are A (Iᴬi), which groups are possible in a child and in what ratio?
A (3/4: IᴬIᴬ, Iᴬi, Iᴬi) and O (1/4: ii) – 3 : 1.
3
How many of 160 F2 four-o’clocks have pink flowers? (Number only.)
80
4
Briefly distinguish epistasis from complementarity.
In epistasis one gene suppresses another; in complementarity two dominant genes act together to produce a new trait.
5
Why is it said that women can also be colour blind, but rarely?
Both X chromosomes need the recessive allele: the father must be colour blind and the mother a carrier or colour blind, which is less common.