Living birds have different method of sex determination than humans do- the ZW c

Question

Living birds have different method of sex determination than humans do- the ZW chromosomal system. In this system, females are heterogametic(meaning, 2 different types of chromosomes for the sex set) sex, while males are homogametic ( meaning, 1 type of chromosome for the sex set) sex. It is plausible to suppose that dinosaurs also had this sex determination method- the ZW method (WW and ZW).

a. A female with a curved horn and a make with a straight horn mate. What are the odds that their son has a straight horn?

b. In a Styracosaurus population, which sex do you expect to have more straight horns?

c. Is it impossible for the other sex to have striahgt horns? Why or why not?

d. A female with a curved horn and a male with a curved horn mate. How would you try and find the genotypes od the parents?

e. Birds do not tend to have trisomy or monosomy diseases in the sex chromosomes. Why do you think that is? What genetic advantage is there to zygote death of individuals with these diseases?

Explanation / Answer

a. 1/2 that their son has a straight horn

b) Males will have more straight horn

c) The other sex can also have straight horns if both the parent have gene for straight horn, or if the male is carrier for the gene (Cc)

d) The genotype of the parent will be cc or Cc

e) Hatching failure happens in case of trisomy or monosomy in sex chromosomes in birds. Having this genetic advantage they don't have unfit or diseased genes in the population.

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