Genetics

Facial dimples and free earlobes are both considered dominant human traits. What are the expected phenotypes of the offspring of a female with dimples and free earlobes (DDFf) and a male with no dimples and attached earlobes (ddff)?

• 50% with dimples and free earlobes and 50% with dimples and attached earlobes
• 50% with dimples and free earlobes and 50% with no dimples and attached earlobes
• 75% with dimples and free earlobes and 25% with no dimples and attached earlobes
• 75% with dimples and attached earlobes and 25% with no dimples and free earlobes

Normal fruit flies have brownish-yellow bodies, and this body color is dominant. A mutation in the gene for body color can produce flies with an ebony body color. A homozygous normal fruit fly (e^te^t) is crossed with a homozygous ebony fruit fly (ee). What is the predicted outcome of this genetic cross?

• All the offspring will have ebony bodies
• Of the offspring, 75% will have brownish-yellow bodies and 25% will have ebony bodies
• All the offspring will have brownish-yellow bodies
• Of the offspring, 75% will have ebony bodies and 25% will have brownish-yellow bodies

In the 1860s Gregor Mendel performed numerous dihybrid crosses between pea plants. Dihybrid crosses involve the study of the inheritance patterns related to two different traits. In guinea pigs the allele for black fur (B) is dominant over the allele for brown fur (b), and the allele for short fur (F) is dominant over the allele for long fur (f). What percentage of the offspring from a BbFf x bbff cross would be expected to be heterozygous for both traits?

• 0%
• 25%
• 50%
• 100%

Tomato plants usually have hairy stems. Hairless stems are present in tomato plants that are homozygous recessive for this trait. If the stem characteristics are determined by a single gene, what is the expected outcome of crossing two tomato plants that are heterozygous for hairy stems?

• 75% hairy stems: 25% hairless stems
• 100% hairy stems
• 100% hairless stems
• 50% hairy stems: 50% hairless stems

If several pea plants with the genotype TTYy are crossed with pea plants with the genotype Ttyy, what percentage of the offspring will be expected to have the TTYy allele combination?

• 25%
• 40%
• 50%
• 75%

In cocker spaniels the allele for a black coat color (B) is dominant over the allele for a brown coat color (b). If a brown cocker spaniel is crossed with a heterozygous black cocker spaniel, which of the following genotypic ratios can be expected?

• 0BB: 2Bb: 2 bb
• 1BB: 2Bb: 1 bb
• 2 BB: 0 Bb: 2 bb
• 2 BB: 1 Bb: 0 bb

• The presence of an additional chromosome
• The presence of a homozygous genotype
• The person's genome
• The person's phenotype