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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Which two genes are most likely to be affected by a crossing-over event?

• a pair of genes located adjacent to each other on a chromosome

• a pair of genes separated by a third gene on a chromosome

• a pair of genes located at opposite ends of a chromosome

• a pair of genes located on different chromosomes

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These homologous chromosomes carry different alleles of the wild type and mutant type in the fruit fly Drosophila.

A cell with the homologous chromosomes undergoes meiosis, and gametes are produced. Is it possible for a chromosome of a gamete to contain the alleles for gray body and brown eyes?

• Yes, because chromosomes are not generally inherited as units.

• No, because chromosomes are always inherited as complete units.

• No, because crossing over occurs only during mitosis, not meiosis.

• Yes, because homologous chromosomes may exchange segments by crossing over during meiosis.

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

• increases

• reduces

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

• haploid

• diploid

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

• chromosomes

• traits

• mitochondria

• hybrids

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