Linked inheritance and sex genetics
Answers are for parents and teachers.
1
Compare linked inheritance with independent inheritance (ratios and cause).
Independent: genes on different chromosomes, test cross 1:1:1:1; linked: on one chromosome, mainly two classes (a few others due to crossing over).
2
A test cross gave 600 flies with 10% crossing over. How many are crossover flies?
60
3
Genes A and B are 12 morganides apart, B and C 5 morganides. What may the A–C distance be (with B between)?
17
4
A woman with normal vision whose father was colour-blind marries a man with normal vision. What is the probability of a colour-blind son among the children?
1/4 (of all children; 1/2 among sons).
5
Which sex chromosome do all of a woman’s sex cells carry? Why?
X; a woman is XX and every egg gets one X in meiosis.