What crosses...

1. When females of a particular mutant strain of Drosophila melanogaster are crossed to wild-type males, all the viable progeny flies are females. Hypothetically, this result could be the consequence of either a sex-linked male-specific lethal mutation or a maternally inherited factor that is lethal to males. What crosses would you perform to distinguish between these alternatives?

Complete dominance

In rabbits, C= agouti coat color, c ^ch=chinchilla, c^h=Himalyan, and c=albino. The four alleles constitute multiple allelic series with complete dominance as follows: the agouti C is dominant to the three other alleles , c is recessive to all other alleles, and chinchilla is dominant to Himalayan. Determine the phenotype of progeny from the following crosses: a) C/c x C/c b) C/c^h x c^h/c c) C/c^ch x C/c

Genotypes

You cross two true breeding strains of zucchini, one with green fruit and the other with yellow. The F1 plants are all green , but when these are crossed, the F2 plants consists of 9 green and 7 yellow. How many genes are involved in determining the zucchini color? Using your own symbols, designate which genotypes yield green and which yield yellow zucchinis.

GENE duplication

Gene duplication is an important evolutionary mechanism and, as result , many cases are known where species has two nearly identical genes.ySuppose there are two genes, A and B , that specify production of the same enzyme. An abnormal phenotype results only if an individual does not make any of that enzyme. What ratio of normal vs abnormal progeny would result from a mating between two parents of the genotype AaBb , where A and B represent alleles that specify production of the enzyme, and a and b are alleles that do not.

Biochemical pathway

You are studying a biochemical pathway in the bread mold NEUROSPORA crassa that is involved in the production of the compound C. You know that compounds A,B,D,E,F are required in this pathway, but you do not know the order in which they are synthesized. In order to study this, you isolate five auxotrophic strains that cannot synthesize compound C. Each of these strains has a single mutation affecting a single step of the pathway. From the following table infer the biochemical pathway and determine in which step each auxotroph has a mutaion. ("+" represents growth of the auxotroph on minimal meduim supplemented with the compund. ("-" represents no growth of the auxotroph on minimal meduim sup... click for more