The interaction of selection and inbreeding in determining the incidence of autosomal recessive diseases. Consider a gene in which recessive mutations occur at a rate of 10^-5. Assume a selective disadvantage S of 0.4 in homozygotes for the recessive allele. Now assume that, for thousands of generations, 10% of all children have been products of first-cousin matings (the remaining 90% being products of random matings). Calculate the steady-state value of q. Also calculate the incidence of the disease at steady state. 

#Question id: 4739

#Unit 8. Inheritance Biology

Inheritance of leaf variegation in the four-o’clock plant, Mirabilis jalapa. the leaves and shoots of one variety of four-o’clock were variegated, displaying a mixture of green and white splotches. If  Flowers on the variegated branches gave rise to

#Question id: 4741

#Unit 8. Inheritance Biology

The F2 progeny from a particular cross exhibit a modified dihybrid ratio of 9 : 7 (instead of 9 : 3 : 3 : 1). What phenotypic ratio would be expected from a testcross of the F1?

#Question id: 4742

#Unit 8. Inheritance Biology

In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?

#Question id: 4743

#Unit 8. Inheritance Biology

Ectrodactyly is an autosomal dominant trait that causes missing middle fingers (lobster claw malformation). A grandfather and grandson both have ectrodactyly, but the intervening father has normal hands by x-ray. Which of the following terms applies to this family?

#Question id: 4744

#Unit 8. Inheritance Biology

Assume that long ear lobes in humans are an autosomal dominant trait that exhibits 50% penetrance. A person who is heterozygous for long ear lobes mates with a person who is homozygous for normal ear lobes. What is the probability that their first child will have long ear lobes.

#Question id: 4745

#Unit 8. Inheritance Biology

In some goats, the presence of horns is produced by an autosomal gene that is dominant in males and recessive in females. A horned female is crossed with a hornless male. The F1 offspring are intercrossed to produce the F2. What proportion of the F2 offspring will have horns?