Miller and Levine Chapter 12: Introduction to Genetics

Mendel studied 7 traits in pea plants. One of the monohybrid crosses he made was between plants with round seeds (R) and plants with wrinkled seeds (r). All of the seeds in the F₁ generation had a round shape.

Next, Mendel allowed the peas in the F₁ generation to self-pollinate, forming the F₂ generation. What describes Mendel's observations and conclusion about the F₂ generation?

• Three fourths of the F₂ plants show the round seed phenotype and carry the dominant allele for roundness.

• One fourth of the F₂ plants show the round seed phenotype and are heterozygous for roundness.

• The F₂ plants are all heterozygous.

• The F₂ plants all have wrinkled seeds, and some carry the allele for round seeds.

Mendel was a careful researcher who studied the inheritance of certain traits in garden peas. Which research practices did Mendel not use?

• He crossed true-breeding pea plants.

• He allowed eggs to be fertilized only by self-pollination.

• He analyzed his data mathematically.

• He controlled variables by studying one or two traits at a time.

The Punnett square shown below describes a cross between two pea plants. The letter T represents the dominant allele for tall plant height, and the letter t represents the recessive allele for short plant height.

What were the genotypes of the parents that produced the offspring in the Punnett square?

• Tt for both parents

• TT for one parent, tt for the other parent

• TT for one parent, Tt for the other parent

• TtTt for both parents

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Study the Punnett square shown here. It describes the potential offspring of a cross between two parents.

What phenotypes will be shown by the offspring?

• All offspring will show the recessive phenotype for this trait.

• All offspring will show the dominant phenotype for this trait.

• Half of the offspring will show the dominant phenotype and half will show the recessive phenotype.

• Three fourths of the offspring will show the dominant phenotype and one fourth will show the recessive phenotype.

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Meiosis is a process that reduces chromosomes to the haploid number, provides genetic _________, and ensures the correct distribution of chromosomes into the gametes.

• stability

• variation

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A human cell that carries a double set of chromosomes is called a _____________ cell. The cell contains 2N = 46, number of chromosomes. One allele of each gene is located on each homologous chromosome. In sexual reproduction, meiosis produces haploid gametes with one of each kind of chromosome. In humans, these cells contain N = 23 number of chromosomes.

• haploid

• diploid

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A yellow seeded, purple flowered heterozygous plant (YyPp) is crossed with a green seeded, white flower plant (yypp). (Y = yellow seed allele; y = green seed allele; P = purple flower allele; p = white flower allele)

What is the probability that an offspring of this cross produces plants with green seeds and white flowers? Assume the traits assort independently.

• 0

• 0.25

• 0.5

• 0.75

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How many different gametes can be produced by a tall, yellow-seeded, purple- flowered, and wrinkled-seeded pea plant? The genotype of the pea plant is TtYyPprr.

• 2

• 4

• 6

• 8

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A plant’s stem length distribution was graphed from the F₁ generation of a cross. Seven categories of stem length phenotypes were observed.

What pattern of inheritance is suggested by the graph?

• polygenic inheritance

• multiple alleles

• codominance

• incomplete dominance

Red blood cells carry antigens on their surfaces coded for by alleles of the gene represented by the letter I. The allele I^A is dominant to i and produces antigen A on the surface of red blood cells. The allele I^B is also dominant to the i allele and produces antigen B on the surface of red blood cells. The i allele does not produce surface antigens.

What are the possible genotypes of a person with type A blood?

I. I^AI^A

II. I^AI^B

III. I^Ai

• III only

• I and II

• I and III

• I, II, and III

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