Question 1

Explain why heterozygotes are expected to be produced twice as frequently as either homozygote in a monohybrid F1 cross.

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Question 2

You observe an individual of your favorite study organism expressing the dominant phenotype for a certain trait. How would you go about determining if the individual was homozygous dominant or heterozygous for that trait?

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Question 3

Mendel selected seven traits to analyze in his famous pea plant crosses, and all of these traits yielded expected 3:1 phenotypic F2 ratios in monohybrid crosses. He was fortunate in his selection of these traits. How so? What problem might he have encountered that may have yielded confusing ratios?

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Question 4

Speculate on the molecular basis for dominance and recessiveness, using flower color as an example, where red is dominant over white.

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Question 5

What are the steps involved in setting up a dihybrid F3 cross?

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Question 6

A monohybrid (1-gene) cross yields 4 genotypic classes, and a dihybrid (2-gene) cross yields 16. How many classes are expected from a tetrahybrid (4-gene) cross?

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Question 7

True-breeding individuals are produced by repeated backcrossing.

Accepted Answer

True-breeding individuals are genetically homozygous and produce offspring with the same traits when self-fertilized or crossed with other true-breeding individuals of the same trait. This can be achieved by repeated backcrossing of individuals with the desired trait.

Question 8

Mendel was the first to describe dominant, recessive, and codominant traits.

Accepted Answer

Mendel described dominant and recessive traits, but the concept of codominance was developed later by other scientists.

Question 9

Mendel was the first scientist to deduce the idea of diploidy-that is, that organisms like pea plants and humans possess two complete sets of genetic material. Summarize Mendel's observations and reasoning that led him to this conclusion.

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Question 10

A monohybrid cross is made for flower color, where purple is dominant to white. Fifteen hundred F2 offspring are analyzed. How many white flowers are expected?

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Question 11

A dihybrid cross yields 200 F2 offspring. How many are expected to resemble the homozygous recessive parental?

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Question 12

The phenotype determines the genotype.

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The genotype determines the phenotype, not the other way around. The genotype is the genetic makeup of an organism, while the phenotype is the physical characteristics that are expressed as a result of the genotype and environmental factors.

Question 13

Mendel's insights started with his approach of analyzing discrete traits, leading to the idea of "particulate" rather than "blending" inheritance. Yet this was an uncommon way to view the inheritance of traits, as many found it counterintuitive or contrary to experience. How so?

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Quiz 20: Gene Expression: Translation