Exam 3: Extensions to Mendels Laws

Achondroplasia is a form of dwarfism in humans. It is caused by a mutant allele of the fibroblast growth factor receptor gene (FGFR) that produces an overactive protein. Having one copy of the mutant allele results in dwarfism. Two copies of the mutant allele results in death before birth. -Based in this information, what can you infer about the inheritance of the FGFR alleles?

In rats, the P gene allele for pigmentation (P) is dominant to the allele for albinism (p). The B gene allele for black pigmentation (B) is dominant to the allele for cream pigmentation (b). The pp homozygous recessive genotype is epistatic to any allele combination at gene B. -Predict the phenotypic ratio of the F₂ progeny of a parental cross between a pure-breeding black rat and an albino that is also homozygous for cream.

What can explain the phenomenon where the same genotype might give rise to different phenotypes?

Some multifactorial traits are determined by many interacting genes, each of which may have several alleles.If such a trait is measured in a population, what phenotypic pattern is expected?

Which genotypic ratio indicates a recessive lethal allele when two heterozygotes are mated?

A particular flower can be purple, blue, red, or white.A pure-breeding purple plant is crossed with a pure-breeding white plant and the F₁ are then crossed to produce an F₂ generation.Which phenotypic ratio in the F₂ may indicate that flower color in these plants is controlled by two genes that interact additively?

A pure-breeding fruit fly with curled wings mates with a pure-breeding fruit fly with normal (straight)wings.The F₁ mate with each other to produce an F₂ generation that consists of 160 flies with curled wings and 80 with straight wings.What can you infer from this observation?

A disease is caused by homozygosity for the g allele (G is the corresponding wild-type allele).However, the penetrance of the disease is 75%.Two individuals known to be heterozygotes have a child.What is the probability that the child exhibits the disease?

Two alleles of gene C control hair color in horses: C¹ and C².Horses homozygous for allele C¹ are red, heterozygotes are yellow, and C² homozygotes are cream.In the offspring of matings between heterozygotes, what phenotypic ratio is expected?

In the common daisy, genes A and B control flower color. Both genes have a dominant allele (A or B) and a recessive allele (a or b). At least one copy of each dominant allele is required for flowers to be colorful instead of white. -Predict the genotypes and phenotypes of the F₁ progeny of a cross between two white-flowered plants, one homozygous for A and the other homozygous for B.

In the common daisy, genes A and B control flower color. Both genes have a dominant allele (A or B) and a recessive allele (a or b). At least one copy of each dominant allele is required for flowers to be colorful instead of white. -Predict the phenotypic ratio of the F₂ progeny of a cross between two white-flowered plants, one homozygous for A and the other homozygous for B.

If a phenotype is controlled by the genotypes at two different loci, a possible interaction between alleles of these genes can be called

In rats, the P gene allele for pigmentation (P) is dominant to the allele for albinism (p). The B gene allele for black pigmentation (B) is dominant to the allele for cream pigmentation (b). The pp homozygous recessive genotype is epistatic to any allele combination at gene B. -Predict the genotypes and phenotypes of the F₁ progeny of a cross between a pure-breeding black rat and an albino that is also homozygous for cream.

What genetic phenomenon might a 2:1 phenotypic ratio indicate?

ABO blood type demonstrates which of the following inheritance patterns? (Select all that apply. )

In some flowers, a purple pigment is synthesized from a red precursor pigment.In the absence of all pigment, flowers are white.A pure-breeding plant with red flowers was crossed to a pure-breeding plant with white flowers.All of the F₁ plants had white flowers.The F₁ plants were crossed to each other, and the F₂ consisted of 165 plants: 123 with white flowers, 32 with purple flowers, and 11 with red flowers.How do these results suggest that flower color is determined?

A particular flower can be purple, blue, red, or white.Two different pure-breeding white plants are crossed and the F₁ are then crossed to produce an F₂ generation.What might a 9:7 phenotypic ratio in the F₂ indicate?

A particular flower can be purple, blue, red, or white.A pure-breeding purple plant is crossed with a pure-breeding white plant and the F₁ are then crossed to produce an F₂ generation.What might a 9:3:4 phenotype ratio in the F₂ indicate?

Two pure-breeding phlox plants were crossed, one with dark-blue flowers and the other with pink flowers. The F1 generation all had dark-blue flowers. When the F1 were crossed with each other, the F2 generation consisted of 176 plants: 101 with dark-blue flowers, 33 with light-blue flowers, 30 with red flowers, and 10 with pink flowers -How is flower color controlled in phlox?

What type of gene interaction determines flower color in primroses?