Question

 

1) The inheritance of curly hair illustrates incomplete dominance. When a curly haired individual reproduces with a straight-haired one, the children all have wavy hair. What offspring would be produced, in what proportions, when two people with wavy hair reproduce?

2) Colorblindness is an X-linked trait recessive disorder. A woman who does not carry the color-blindness allele has children with a man who is color blind. What proportion of their children will be color blind?

3) Huntington disease (HD) is an autosomal dominant disorder. A person who is heterozygous for the Huntington disease allele has offspring with someone who does not have HD. What proportion of their children will have HD?

Answer 1

Answer 1) incomplete dominance occurs when 2 homozygous individuals are crossed and they results in heterozygous having an intermediate phenotype like here when curly haired individual reproduces with a straight-haired one, the children all have wavy hair. Now as we know that here wavy is heterozygote and when 2 heterozygotes are crossed i.e when two people with wavy hair reproduce than their offsprings will have genotype of 1:2:1 ratio.
Therefore, the offspring will curly hair will be 1/4 as they are homozygous dominant allele, offsprings with wavy hairs will be 1/2 having heterozygous alleles and offsprings with straight hairs will be 1/4 having homozygous recessive allele.

Answer 2) Here normal women genotype is X+X+ and affected male genotype is XcY. Therefore there cross will results into 1/2 affected offsprings.
X+X+ * XcY
X+Xc X+Y X+Xc X+Y
In X- linked inheritance, the characters are determined by X chromosome as the name suggests. The characters or disorders are passed from affected or carrier mother to the affected son because they the X is inherited from the mother. And males get more affected in this but in X linked disorders are never passed from father to son. So here is a 50% chance that daughters are affected by affected father.