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End of Chapter 3 Problems

Question 1.

Why was Mendel’s approach to the study of heredity so successful?

He chose to work with a plant that was easy to cultivate, grew relatively rapidly, and produced many offspring whose phenotype was easy to determine.

The seven characteristics he chose to study were important because they exhibited only a few distinct phenotypes and did not show a range of variation.

By looking at each trait separately and counting the numbers of the different phenotypes, he was able to detect mathematical ratios of progeny phenotypes.

He adopted an experimental approach and applied the scientific method. From his observations, he proposed hypotheses that he was then able to test empirically.

All of the above

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Question 2.

What is the difference between genotype and phenotype?

Phenotype refers to the physical manifestation of a trait, whereas genotype refers to the genes or sets of alleles found within an individual.

Phenotype refers to the sets of alleles found within an individual, whereas genotype refers to the physical expression of a trait.

Genotype refers to the physical expression of the genes or sets of alleles found within an individual, whereas phenotype refers to the physical manifestation of a trait.

Genotype refers to the physical location of a gene on a chromosome, whereas phenotype refers to the total number of alleles found within an individual.

Genotype and phenotype are essentially two terms for the same thing.

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Question 3.

What is the principle of segregation? Why is it important?

The principle of segregation proposes that offspring are the result of blended genetic material from the parent and the genetic factors are not discrete units. It explains how the genotypic ratios in the diploid gametes are produced.

The principle of segregation states that a diploid organism possesses two alleles for any one particular trait and that these alleles separate during the formation of gametes. It explains how the genotypic ratios in the haploid gametes are produced.

The principle of segregation states that genes for different characteristics that are at different loci segregate independently of one another. It explains the phenotypic ratios seen in the diploid parents.

The principle of segregation states that genes are located on chromosomes. It explains how genes are passed on from parent to offspring.

The principle of segregation proposes that once genetic material is blended, it cannot be separated. It explains how the genotypic ratios of offspring are produced.

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Question 4.

How are Mendel’s principles different from the concept of blending inheritance discussed in Chapter 1?

According to Mendel’s principles, alleles (or genetic factors) are discrete units that remain separated within an individual organism.

According to the concept of blending inheritance, offspring result from a blending of their parents’ genetic material.

According to the concept of blending inheritance, once blended, the genetic material from each parent is no longer discrete units that remain separated within an individual organism.

According to the concept of blending inheritance, genetic material once blended cannot be separated in future generations.

All of the above are differences between Mendel’s principles and the concept of blending inheritance.

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Question 5.

What is the concept of dominance?

The concept of dominance states that when two different alleles are present in a genotype, both alleles can be observed equally in the phenotype.

The concept of dominance states that recessive alleles are only visible in the heterozygous condition.

The concept of dominance states that when two different alleles are present in a genotype, only the dominant allele is observed in the phenotype.

The concept of dominance states that an organism can only exhibit two alleles at a time.

None of these statements accurately explains the concept of dominance.

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Question 6.

What are the addition and multiplication rules of probability and when should they be used?

The addition rule states that:

The probability of two mutually exclusive events occurring together is the product of their probabilities of occurring independently

The probability of any one of two mutually exclusive events can be determined by adding the probabilities of these events

When is the addition rule useful?

It is useful in predicting the genotypic ratios

It is useful in predicting phenotypic ratios

The multiplication rule states that:

The probability of two mutually exclusive events occurring together is the product of their probabilities of occurring independently

The probability of any one of two mutually exclusive events can be determined by adding the probabilities of these events

When is the multiplication rule useful?

It is useful in predicting the genotypic ratios

It is useful in predicting phenotypic ratios

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Question 7.

Which of the following crosses would likely produce a genotypic ratio of 1:2:1?

Aa × Aa

Aa × aa

AA × Aa

aa × aa

No correct answer is listed.

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Question 8.

Which of the following crosses would likely produce a genotypic ratio of 1:1?

Aa × Aa

Aa × aa

AA × aa

aa × aa

No correct answer is listed.

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Question 9.

The chromosome theory of heredity states that

DNA is the genetic material.

genes are inherited from a common ancestor.

chromosomes segregate during mitosis.

genes are located on chromosomes.

chromosomes are made of DNA and protein.

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Question 10.

Why was the chromosome theory of heredity important?

Figure 1.1 (above) shows three girls, one of whom has albinism. Could the three girls shown in the photograph be sisters? Why or why not?

Yes, the girls could be sisters. Albinism is known to show up more often in males than females, so these children could be sisters since most of them have normal pigmentation.

Yes, the girls could be sisters. Albinism is inherited as an autosomal recessive trait, so the children could be sisters if the parents were heterozygous.

No, the girls could not be sisters. The frequency of albinism is very rare, only 1 in 20,000 persons, so it is not likely that they are sisters.

No, the girls could not be sisters. Hopi parents never had more than one child, so the child with albinism could not have had any sisters.

Not enough information is given to know whether or not they could possibly be sisters.

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Chapter 1. End of Chapter 3 Problems

Instructions

Introduction to Heredity

Question 1.

Question 2.

Question 3.

Question 4.

Question 5.

Question 6.

Question 7.

Question 8.

Question 9.

Question 10.

Introduction to Heredity (continued)

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Question 12.

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Question 21.