Hfr strains

In E.coli, four streptomycin-sensitive, prototrophic Hfr strains were mated with a stretomycin-resistant F^- strain auxotrophic for a number of nutritonal requirements. Matings were interrupted at various intervals, and cells were plated on streptomycin-containing minimal meduim supplemented with particular nutrients to test for ...continues

Map Distances

Time of entry mapping between a streptomycin-sensitive, prototrophic Hfr strain and a streptomycin- resistant Fminus strain that was Trp- Pyr- Cys- Nic- did not allow the order of the trp,pyr,cys genes to be determined, but these three genes were always transferred before nic. To determine the relative order of the trp,pyr,cys g ...continues

E.coli

A nutritionally defective E.coli strain grows only on meduim containing thymine, whereas another nutritionally defective strain grows only on meduim containing leucine. When these two strains are grown together , a few progeny are able to grow on minimal meduim with neither leucine nor thymine. How can this result be explained?

A recessive mutation in the human genome...

1. A recessive mutation in the human genome results in a condition called anhidrotic ectodermal dysplasia, which is associated with an absence of sweat glands. The condition can be detected by studies of the electrical conductivity of the skin, because skin without sweat glands has a lower electrical conductivity (higher resist ...continues

Grandchildless

1. You have isolated a recessive Drosophila mutant that you call grandchildless (gls) because it behaves in the following way: Cross: gls/gls female x +/+ male F1: All sterile If you perform the reciprocal cross, however, you find that the result is different from that in cross 1: Cross: gls/gls male x +/+ female ...continues

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 woul ...continues

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 pro ...continues

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 an ...continues

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 ...continues

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 syn ...continues