Exam 4: Gene Mapping in Eukaryotes

In the ABO blood-type system, which genotypes could confer type A blood to a person?

Studies performed on identical twins separated at birth have shown that many phenotypes, such as IQ or alcoholism, are influenced by the person's genotype as well as by their environment.

A true-breeding red-flowered plant is fertilized by a true-breeding white-flowered plant and produces all pink-flowered offspring. This is a case of

In a genotype with complete penetrance, less than 100 percent of individuals with a particular genotype exhibit the expected phenotype.

Comb shape in chickens is controlled by

In a dihybrid cross with independent assortment of the two genes, any deviation from the Mendelian 9:3:3:1 ratio indicates that the phenotype is the product of the interaction of two or more genes.

What is the cause of Tay-Sachs disease?

A person who is known to have a particular genotype does not show the phenotype specified by the gene. This is an example of

Individuals with neurofibromatosis may have a range of phenotypes, from pigment spots on the skin to tumorlike growths. This is an example of

If the offspring above was crossed with one another, what would be the ratio of phenotypes in the F2 generation?

Dogs have one gene that controls how much melanin is produced, a second gene that controls whether melanin is deposited in the fur, and a third gene that controls whether melanin is produced at all. What do you call the interaction of these three genes?

In a multiple allelic system for eye color in Drosophila, the phenotypic expression of the alleles depends on

What is the number of possible genotypes in a multiple allele series with six alleles? How many of these are homozygous and how many are heterozygous?

Feather color in chickens is the result of an incompletely dominant gene. The gene responsible for black feathers (B) when homozygous results in a muted color called "Andalusian blue" if combined with an allele for white feathers (b). When the white allele occurs in homozygous condition, a white phenotype results. A gene affecting comb shape (R), which results in a comb called a "rose" comb, is completely dominant over (r), which in homozygous conditions results in a comb called "single." A mating between a black single rooster and white rose hen results in a number of chicks, all of which have identical phenotypes. What is the phenotype and genotype of the chicks?

How can a fatal autosomal dominant genetic disorder, like Huntington's disorder, be passed on to the next generation?

How could a man with blood type A and a woman with blood type B produce a child with blood type O?

The 9:6:1 F2 ratio found in fruit shape in summer squash is a deviation from an expected Mendelian ratio. What does this represent?

Novel phenotypes may arise when

Why is it that males and females who are both heterozygous for the pattern-baldness gene have different phenotypes (males are bald, females are not bald)?

Two true-breeding mutant strains of Drosophila have black body color instead of the wild-type gray yellow. When the two strains are crossed, all the F1 flies have wild-type body color. How can these data be interpreted?