Exam 12: Inheritance, Genes, and Chromosomes

When two strains of bacteria with genotypes ABcd and abCD are grown together in the lab, a small number of bacteria with the genotype ABCD eventually arise.How does this likely occur?

A cross between two parents that differs by a single trait is called a(n) _______ cross.

Mendel concluded that each pea has two units for each character, and each gamete contains one unit.Mendel's "unit" is now referred to as a

Which phenomenon tends to decrease the number of phenotypic classes in dihybrid crosses?

Sometimes scientists get lucky.Consider Mendel's dihybrid cross shown in the figure. Peas have a haploid number of seven chromosomes, so many of their genes are linked.What would Mendel's results have been if the genes for seed color and seed shape were linked with a map distance of 14 units?

Female Drosophila that have vermillion eyes are crossed with males that have wild-type eyes.If this allele is recessive and X-linked, then _______ percent of the sons should have vermillion eyes.

In tomatoes, tall is dominant to dwarf, and smooth fruits are dominant to hairy fruits.A plant homozygous for both dominant traits is crossed with a plant homozygous for both recessive traits.The F₁ progeny are test-crossed with the following results in the F₂ progeny: 96 tall with smooth fruits; 94 dwarf with hairy fruits; 6 tall with hairy fruits; and 4 dwarf with smooth fruits.These data indicate that the genes are

Incomplete dominance

Geneticists have discovered the existence of meiotic drive genes, which have alleles that, when present in a heterozygous state, are able to become incorporated into much more than 50 percent of the gametes.As a result, the offspring ratios are not what Mendel would have predicted.Suppose that the short allele is a meiotic drive gene, and 80 percent of the gametes from a heterozygous individual with tall and short alleles contain short alleles.If tall is dominant to short, what percent of individuals from a cross between a heterozygous tall individual and a homozygous recessive individual will be tall?

In cocker spaniels, black color (B) is dominant over red (b), and solid color (S) is dominant over spotted (s).If the genes are unlinked and the offspring of BBss and bbss individuals are mated with each other, what fraction of their offspring will be black and spotted?

Agouti is a type of coat color pattern in mice that cannot be expressed in albinos (white mice).A nonalbino agouti mouse that is heterozygous at the albino (A) and agouti (B) loci (AaBb) is mated to an albino mouse that is heterozygous at the agouti locus (aaBb).Nonalbino mice without the dominant agouti allele (AAbb and Aabb) are black.What percent of the progeny would you expect to be black?

Locus A and locus B recombine with 10 percent frequency.Locus A and locus C recombine with 23 percent frequency.Locus B and locus D recombine with 4 percent frequency.Locus D and Locus E are not observed to recombine.Based on this information, what is the expected frequency of recombination between locus B and locus E?

If bacterial conjugation is allowed to take place for more than an hour, two different genes (A and B) are conjugated.If, however, conjugation occurs for only a few minutes, only A or only B can be conjugated.Based on this information, which situation is most likely?

Coat color in mice involves the effects of multiple gene interactions.If a mouse has two recessive alleles (aa) for coat color, it will always be albino no matter what the genotype of other genes involved in coat color.This is an example of

Egg and Fluffy are two linked bird genes that are 16 map units apart.The E allele of Egg produces large eggs, and the e allele produces small eggs (E is dominant).The F allele produces fluffy feathers, and the f allele produces nonfluffy feathers (F is dominant).If EEFF is crossed with eeff, what proportion of the offspring should be birds that produce large eggs and fluffy feathers?

The site on the chromosome occupied by a gene is called a(n)

When many genes contribute to the phenotype, variation is said to be continuous, or _______.

Assume that blending inheritance, not particulate Mendelian inheritance, is operating in a life form.An individual with a tail that is 10 centimeters long is crossed with an individual that has a tail 2 cm long.What would the expected tail length be in the F₂ progeny?

Consider the case of X-linked inheritance of a recessive mutant allele.Among progeny from a cross of an unaffected male and a heterozygous female carrier,

If Mendel had performed experiments on cattle rather than on peas, the patterns of inheritance would not have been easily detectable, because cattle