Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.
The serine biosynthetic pathway is a three-step pathway in which each step is catalyzed by the enzyme product of a different gene, identified as enzymes A, B, and C in the diagram below.



Mutant 1 grows only on min + Ser. In addition to growth on min + Ser, mutant 2 also grows on min + 3-PHP and min + 3-PS. Mutant 3 grows on min + 3-PS and min + Ser. Identify the step of the serine biosynthesis pathway at which each mutant is defective.

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.

The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine (min + Ser), and all three colonies grow. Characterize these three colonies.

When working on barley plants, two researchers independently identify a short-plant mutation and develop homozygous recessive lines of short plants. Careful measurements of the height of mutant short plants versus normal tall plants indicate that the two mutant lines have the same height. How would you determine if these two mutant lines carry mutation of the same gene or of different genes?

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

c. What are the genotype(s) and phenotype(s) of the F₁ progeny of the cross described in part (b)?

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

a. List the genotypes for green, yellow, blue, and albino budgies

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.

Using terminology, characterize the 12 colonies that grow on minimal medium and the 3 colonies that do not.

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

b. A cross is made between a pure-breeding green budgie and a pure-breeding albino budgie. What are the genotypes of the parent birds?