Question 1

Sex-limited traits are caused by genes that are on sex chromosomes.

Accepted Answer

Sex-limited traits are influenced by genes located on autosomal chromosomes but are expressed in only one sex due to hormonal differences between the sexes, not because they are located on sex chromosomes.

Question 2

What is the cause of Tay-Sachs disease?

Accepted Answer

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Question 3

For a gene with multiple alleles,what is the maximum number of alleles that a diploid organism may have?

Accepted Answer

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Question 4

How could a man with blood type A and a woman with blood type B produce a child with blood type O?

Accepted Answer

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Question 5

In a dihybrid cross with independent assortment of the two genes,any deviation from the Mendelian 9:3:3:1 ratio indicates that the phenotype is the product of the interaction of two or more genes.

Accepted Answer

The Mendelian 9:3:3:1 ratio is expected in a dihybrid cross with independent assortment of the two genes. Any deviation from this ratio indicates that the phenotype is the product of the interaction of two or more genes.

Question 6

In the human ABO blood system,the allele i is dominant to I^A and I^B.

Accepted Answer

The allele i is actually recessive to both I^A and I^B in the ABO blood system.

Question 7

Explain and differentiate among the molecular bases of codominance,incomplete dominance,and complete dominance.

Accepted Answer

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Question 8

Feather color in chickens is the result of an incompletely dominant gene. The gene responsible for black feathers (B) when homozygous results in a muted color called "Andalusian blue" if combined with an allele for white feathers (b). When the white allele occurs in homozygous conditions, a white phenotype results. A gene affecting comb shape (R), which results in a comb called a "rose" comb, is completely dominant over (r), which in homozygous conditions results in a comb called "single." A mating between a black single rooster and white rose hen results in a number of chicks, all of which have identical phenotypes. -Use a Punnett square to demonstrate a cross between two of the F₁ offspring.What are the phenotypes and ratios that occur?

Accepted Answer

The answer of Feather color in chickens is the result...

Question 9

Phenylketonuria (PKU)is an example of a phenotype that is solely influenced by genes.

Accepted Answer

Phenylketonuria (PKU) is a genetic disorder that results from mutations in the gene responsible for producing the enzyme phenylalanine hydroxylase. However, the phenotype of PKU is also influenced by environmental factors, specifically the intake of foods containing phenylalanine. Individuals with PKU must follow a strict low-phenylalanine diet to prevent the harmful effects of excess phenylalanine on brain development. Therefore, the phenotype of PKU is a result of both genetic and environmental factors.

Question 10

Recessive lethals are often mutations in essential genes.

Accepted Answer

Recessive lethals are mutations in genes that are essential for normal development or survival. These mutations can only cause lethality when they occur in the homozygous state, as a single functional copy of the gene is usually sufficient for normal function. Examples of recessive lethals include mutations in genes involved in embryonic development or vital metabolic processes.

Question 11

What is the number of possible genotypes in a multiple allele series with 6 alleles? How many of these are homozygous and how many are heterozygous?

Accepted Answer

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Question 12

In a genotype with complete penetrance,less than 100% of individuals with a particular genotype exhibit the expected phenotype.

Accepted Answer

In a genotype with complete penetrance, 100% of individuals with a particular genotype exhibit the expected phenotype. There is no variation in expression of the phenotype within the population.

Question 13

Generally,blue eyes are recessive to dark brown eyes in humans.Individuals with albinism typically have blue eyes with a strong red reflection.A blue-eyed woman with albinism marries a man who is blue-eyed but does not have albinism.All their children have dark brown eyes.How can this be explained?

Accepted Answer

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Question 14

Feather color in chickens is the result of an incompletely dominant gene. The gene responsible for black feathers (B) when homozygous results in a muted color called "Andalusian blue" if combined with an allele for white feathers (b). When the white allele occurs in homozygous conditions, a white phenotype results. A gene affecting comb shape (R), which results in a comb called a "rose" comb, is completely dominant over (r), which in homozygous conditions results in a comb called "single." A mating between a black single rooster and white rose hen results in a number of chicks, all of which have identical phenotypes. 
-What is the phenotype and genotype of the chicks?

Accepted Answer

The answer of Feather color in chickens is the result...

Question 15

In chickens,there is a mutant gene called "frizzle" that results in weak,stringy,and easily broken feathers.When a frightfully frizzled fowl is bred to a normal chicken,the offspring are all mildly frizzled.If one breeds two mildly frizzled chickens to each other,the offspring have the phenotypic ratio of 1 normal: 2 mildly frizzled: 1 frightfully frizzled.What is the mode of inheritance of "frizzle"?

Accepted Answer

The answer of In chickens,there is a mutant gene called...

Question 16

In cats,the dominant white gene (W)may or may not also cause deafness.Homozygotes are more likely to be deaf than heterozygotes.If you breed heterozygous white cats together and produce 100 kittens,how many would you expect to be deaf if all the proportions came out perfectly? Assume that heterozygotes have an 8% chance of being deaf,and homozygotes a 60% chance of being deaf.

Accepted Answer

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Question 17

Why is it that human males and females who are both heterozygous for the pattern-baldness gene have different phenotypes (males are bald,females are not bald)?

Accepted Answer

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Question 18

In the ABO blood-type system,which genotypes could confer type A blood to a person?

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Question 19

Comb shape in chickens also involves the interaction of two genes,but the F₂generation shows a typical 9:3:3:1 Mendelian ratio.How does this work?

Accepted Answer

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Question 20

The 9:6:1 F₂ ratio found in fruit shape in summer squash is a deviation from an expected Mendelian ratio.What does this represent?

Accepted Answer

The answer of The 9:6:1 F₂ ratio found in fruit...

Quiz 13: Extensions of and Deviations From Mendelian Genetic Principles