3.4 Inheritance

Mice with the same parents can have different traits. Which of the following best explains how most of these differences occur?

• Gametes join by binary fission.

• Cells divide by asexual reproduction.

• Genes assort independently during meiosis.

• Spontaneous mutations occur during mitosis.

Six puppies from a single litter have the following genotypes for a certain trait: AA, Aa, AA, aa, aa, Aa. Which of the following describes how these alleles were passed on from parent to offspring?

• Each parent dog randomly passed on a dominant allele (A) or a recessive allele (a) to each offspring.

• The male dog passed on a dominant allele (A) to each female offspring and a recessive allele (a) to each male offspring.

• The female dog chose to pass on either homozygous dominant alleles (AA) or homozygous recessive alleles (aa) to each offspring.

• One parent dog passed on a dominant allele (A) to each offspring, and the other parent dog passed on a recessive allele (a) to each offspring.

Many ranchers prefer cattle without horns. The presence or absence of horns is genetically determined. The allele for the absence of horns (A) is dominant to the allele for the presence of horns (a). A male with horns is mated with a heterozygous female without horns. What percentage of the offspring would be expected to have horns?

• 25%

• 50%

• 75%

• 100%

The pictures show two types of hairlines that children can inherit from their parents. The allele for a widow’s peak hairline (W) is dominant, and the allele for a straight hairline (w) is recessive. If both parents are heterozygous (Ww) for this trait, what is the probability that their child will have a straight hairline?

• 0%

• 25%

• 50%

• 75%

In squash plants, the allele for yellow fruit (Y) is dominant to the allele for green fruit (y). A plant with genotype YY is crossed with a plant with genotype Yy.

What are the expected genotype percentages in the offspring of this cross?

• 100% heterozygous and 0% homozygous

• 50% homozygous dominant and 50% heterozygous

• 50% homozygous dominant and 50% homozygous recessive

• 25% homozygous dominant, 50% heterozygous, and 25% homozygous recessive

The table gives information about the genetics of white spotting in cats. If a partially white cat mates with a black cat, what are the expected phenotypes of the kittens?

• All the kittens will be black.

• Half the kittens will be black, and half will be partially white.

• Three-quarters of the kittens will be black, and one-quarter will be partially white.

• Three-quarters of the kittens will be partially white, and one-quarter will be mostly white.

Which is the set of alleles that an individual possesses?

• A gene
• A genotype
• A genome
• A genus

What is a genetic test cross?

• Testing an unknown genotype by crossing it with a known heterozygote

• Testing an unknown genotype by crossing it with a known heterozygote

• Testing an unknown genotype by crossing it with a known homozygous dominant

• Testing an unknown genotype by crossing it with a known homozygous recessive

The ABO blood grouping system has alleles of I^A, I^B and i. What is this an example of?

• Sex-linkage

• Codominance

• Gene linkage

• Polygenetic traits

A parent organism of unknown genotype is mated in a test cross.  Half of the offspring have the same phenotype as the parent.  What can be concluded from this result?

• The parent of unknown genotype is heterozygous
• The parent of unknown genotype is homozygous dominant
• The parent of unknown genotype is homozygous recessive
• The parent of known genotype is heterozygous

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