Unit 8.5 Quiz 7

The purpose of selective breeding is to produce:

• bigger animals.

• smaller animals.

• animals with desirable traits.

• animals with bad traits.

Answer explanation

Selective breeding aims to enhance specific traits in animals, leading to the production of animals with desirable traits. This process allows breeders to cultivate characteristics that are beneficial for agriculture, companionship, or other purposes.

Which term describes an allele that masks the expression of another allele when present in the genotype?

• dominant

• co-dominant

• incompletely dominant

• recessive

Answer explanation

The term 'dominant' describes an allele that can mask the expression of another allele in the genotype. When a dominant allele is present, its traits are expressed, overshadowing those of the recessive allele.

Two plants are crossed: one with genotype RR (red) and another with genotype rr (white). All offspring have genotype Rr. R is dominant, and r is recessive. What can be concluded about the color of the offspring?

• They will be red.

• They will be pink.

• They will be white.

• Half will be red and half will be white.

• They will be red with white speckles.

Answer explanation

The offspring with genotype Rr will express the dominant trait, which is red color. Therefore, all offspring will be red.

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In a breeding program, a bull with genotype EE is mated with a cow with genotype ee. What is the probability that their offspring will have the genotype ee?

• 0%

• 25%

• 50%

• 75%

• 100%

Answer explanation

The bull has genotype EE, contributing only E alleles, while the cow has genotype ee, contributing only e alleles. Therefore, all offspring will have genotype Ee, making the probability of ee offspring 0%.

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Co-dominance differs from incomplete dominance in that:

• co-dominance shows a blending of traits, while incomplete dominance shows clear dominance.

• co-dominance results in a heterozygous phenotype distinct from either homozygous phenotype.

• co-dominance results in a 3:1 phenotypic ratio, while incomplete dominance results in a 1:2:1 ratio.

• co-dominance involves multiple alleles, while incomplete dominance involves only two alleles.

Answer explanation

Co-dominance results in a heterozygous phenotype that expresses both traits distinctly, unlike incomplete dominance, which blends traits. This makes the correct choice highlight the unique phenotype in co-dominance.

Which of the following is an example of artificial selection?

• Wild wolves evolving into domestic dogs through natural environmental pressures.

• A population of birds developing different beak shapes due to natural food sources.

• A mutation causing antibiotic resistance in bacteria.

• Breeding only dairy cows that produce high milk yields.

Answer explanation

Breeding only dairy cows that produce high milk yields is an example of artificial selection, as it involves human intervention to select traits, unlike the other options which describe natural processes.

A farmer has bred only his cattle with extra big muscles to produce cattle with extra big muscles. What is this an example of?

• Punnett squares

• pedigree charts

• natural selection

• artificial selection

Answer explanation

This is an example of artificial selection, where the farmer selectively breeds cattle with desirable traits (extra big muscles) to enhance those traits in future generations, unlike natural selection which occurs without human intervention.

Which statement about DNA is correct?

• A child's DNA will show similarities to both the mother's and father's DNA.

• A child's DNA will be unrelated to the mother's or father's DNA.

• A female child's DNA will exactly match the mother's DNA.

• A male child's DNA will exactly match the father's DNA.

Answer explanation

A child's DNA is inherited from both parents, containing a mix of their genetic material. This means a child's DNA will show similarities to both the mother's and father's DNA, making the first statement correct.

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