7.2 Polygenic Trait practise

A scientist collects data on skin pigmentation in a large population. The data are represented in the table below. Levels of pigmentation were evaluated on a scale from 1 (lightest) to 10 (darkest). Based on the data, what is the best explanation for the variation in pigmentation levels in this population?

• One gene is controlling the expression of another gene.

• Skin pigmentation levels are inherited as a polygenic trait.

• One allele with multiple genes is controlling the expression of the trait.

• Skin pigmentation levels are an example of a codominant pattern of inheritance.

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How does offspring prediction for polygenic inheritance compare to simple inheritance?

• Simple inheritance has more contributing alleles, so it is harder to predict.

• Polygenic inheritance and simple inheritance are equally difficult to predict.

• Polygenic inheritance is easier to predict because there are fewer alleles that determine the trait.

• Polygenic inheritance is more difficult to predict because there are multiple genes that determine the trait.

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Why is there a wide range of skin tones within the human population?

• The trait for skin color is controlled by polygenic inheritance.

• The trait for skin color is controlled by codominance inheritance.

• The trait for skin color is controlled by complete dominance inheritance.

• The trait for skin color is controlled by incomplete dominance inheritance.

A human population shows a wide range of hair shades, from very light to very dark, with most individuals having medium shades. What does this pattern reveal about the inheritance of hair color?

• Hair color is environmental, changing completely with exposure to sunlight.

• Hair color is random, showing no consistent genetic influence in the population.

• Hair color is a single-gene trait, with one dominant allele that controls all shade variations.

• Hair color is a polygenic trait, and the most common phenotypes result from mixed allele combinations.

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Which is a characteristic of polygenic traits?

• A single allele determines the trait.

• Multiple alleles determine the trait.

• Only genotypes, not phenotypes, are expressed.

• External influences have no effect on phenotypes.

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A range of human eye colors is shown. Which statement BEST describes the inheritance pattern of eye colors?

• It is a polygenic trait because it is inherited on a single gene.

• It is a monogenic trait because it is inherited on a single gene.

• It is a polygenic trait because it is influenced by two or more genes.

• It is a monogenic trait because it is influenced by two or more genes.

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The image shows adults from the same family. Use the drop-down menus to describe why adults from the same family vary in height: The height of a person is controlled by​​ ​ ​ ​ (a)   inheritance. Each gene involved in height plays a ​ (b)   role in the expression of the trait. Select the correct combination for 1 and 2.

​ ​

• large
• monogenic
• Polygenic
• Small

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The image shows a Punnett square for eye color. According to the Punnett square, how many possible phenotypes result from a cross between a mother and father with heterozygous genotypes?

• 4

• 5

• 9

• 16

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Which of the following best explains why traits like height in humans show a continuous range of variation?

• Height is determined by a single gene with two alleles.

• Height is an example of codominance inheritance.

• Height is influenced by multiple genes, each contributing to the phenotype.

• Height is only affected by environmental factors and not genetics.

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What pattern would you expect to see in a graph showing the distribution of a polygenic trait in a large population?

• A bell-shaped curve with most individuals having intermediate trait values.

• A uniform distribution with equal numbers for all trait values.

• A bimodal distribution with two distinct peaks.

• A single peak at one extreme of the trait range.

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