Bio Test 2 (Part 5)

2.

The rold of environmental factors on gene expression is illustrated by the

Varying plant height of genetically identical yarrow plants when grown at different elevations.
Flower color of hydrangeas grown in soils of differing pH.
Depression response that some persons make to very stressful situations.
Fur pattern of Himalayan rabbits.
All of these.

Correct Answer

A. All of these.

Explanation

The correct answer is "all of these". This is because all the given examples demonstrate the influence of environmental factors on gene expression. The varying plant height of genetically identical yarrow plants at different elevations shows how the environment can affect the expression of genes related to growth. The flower color of hydrangeas changing in soils of differing pH indicates that the environment can influence the expression of genes responsible for pigment production. The depression response to stressful situations suggests that environmental factors can impact the expression of genes related to mental health. Lastly, the fur pattern of Himalayan rabbits being influenced by temperature demonstrates how the environment can affect gene expression related to pigmentation.

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3.

In cocker spaniels, black coat color (B) is dominant over red (b), and solid color (S) is dominant over spotted (s). If a solid red male is crossed with a solid black female to produce a red, spotted puppy, the genotypes of the parents (with male genotype first) will be

Bb Ss : Bb Ss
Bb Ss : Bb Ss
Bb ss : Bb Ss
Bb Ss : Bb ss
Bb ss : Bb ss

Correct Answer

A. Bb Ss : Bb Ss

Explanation

The given answer bb Ss : Bb Ss is correct because the male dog is solid red, which means it must have the genotype bb for coat color. The female dog is solid black, so she must have the genotype Bb for coat color. The puppy is red and spotted, which means it must have the genotype bb for coat color and Ss for coat pattern. Therefore, the genotypes of the parents are bb Ss : Bb Ss.

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4.

A color-blind man and a woman with normal vision whose father was color blind have a son. Color blindness, in this case, is caused by an X-linked recessive gene. If only the male offspring are considered, the probability that their son is color blind is

.25 (or 25 percent)
.50 (or 50 percent)
.75 ( or 75 percent)
1.00 (or 100 percent)
None of these.

Correct Answer

A. .50 (or 50 percent)

Explanation

The probability that their son is color blind is .50 (or 50 percent) because color blindness is caused by an X-linked recessive gene. Since the father is color blind, he must have one X chromosome with the recessive gene. The mother, who has normal vision, must have two normal X chromosomes. When they have a son, he will inherit one X chromosome from his mother and one Y chromosome from his father. Since the son inherits the recessive gene from his father, he will be color blind. Therefore, the probability of their son being color blind is 50 percent.

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5.

Genes that are located on the same chromosome

Tend to be inherited together.
Will appear together in the gamete.
Are said to be linked.
May be seperated during crossing over.
All of these.

Correct Answer

A. All of these.

Explanation

Genes that are located on the same chromosome tend to be inherited together because they are physically linked on the same DNA molecule. During the formation of gametes, the chromosome pairs separate and are randomly distributed, so the genes on the same chromosome will appear together in the gamete. This phenomenon is known as genetic linkage. However, during the process of crossing over, genetic material can be exchanged between homologous chromosomes, leading to the separation of linked genes. Therefore, all of the given statements are correct explanations for genes located on the same chromosome.

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6.

An autosomal recessive disorder

Requires that only one parent be a carrier.
Displays its symptoms only in heterozygotes.
Is more frequent in males than females.
Will appear only in children of parents who both carry the gene.
Is dominant in females.

Correct Answer

A. Will appear only in children of parents who both carry the gene.

Explanation

An autosomal recessive disorder will appear only in children of parents who both carry the gene because it requires two copies of the gene, one from each parent, in order to manifest. If only one parent carries the gene, they will be a carrier but not affected by the disorder themselves. However, if both parents are carriers, there is a 25% chance that their child will inherit two copies of the gene and therefore develop the disorder.

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7.

If a daughter expresses an X-linked recessive gene, she inherited the trait from

Her mother.
Her father.
Both parents.
Neither parent.
Her grandmother.

Correct Answer

A. Both parents.

Explanation

If a daughter expresses an X-linked recessive gene, it means she has inherited a faulty gene located on the X chromosome. Since females have two X chromosomes, one from each parent, they can inherit the faulty gene from both their mother and their father. This is why the correct answer is both parents.

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8.

Genes at one locus that affect the expression of genes at a different locus are said to be

Epistatic.
Linked.
Codominant.
Penetrant.
Alleles.

Correct Answer

A. Epistatic.

Explanation

Genes at one locus that affect the expression of genes at a different locus are said to be epistatic. Epistasis refers to the phenomenon where the alleles of one gene mask or modify the effects of alleles of a different gene. This interaction between genes can result in a wide range of outcomes, including the suppression or enhancement of certain traits. Epistasis is important in understanding the complexity of genetic inheritance patterns and the variation observed in phenotypes.

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9.

Some dogs have erect ears; others have drooping ears. Some dogs bark when following a scent; others are silent. Erect ears and barking are due to dominant alleles located on different chromosomes. A dog homozygous for both dominant traits is mated to a droopy-eared, silent follower. The expected phenotypic ration in the F1 generation is

9:3:3:1
100 percent of one phenotype
1:1
1:2:1
None of these

Correct Answer

A. 100 percent of one phenotype

Explanation

In this scenario, the traits of erect ears and barking are controlled by dominant alleles located on different chromosomes. When a dog that is homozygous for both dominant traits (erect ears and barking) is mated with a dog that has droopy ears and is silent, all the offspring in the F1 generation will inherit the dominant traits from the homozygous parent. Therefore, the expected phenotypic ratio in the F1 generation will be 100 percent of one phenotype, which means that all the offspring will have erect ears and bark.

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10.

A graph of phenotypic variation similar to the illustration below strongly suggests

Incomplete dominance.
Codominance.
Epistasis.
Polygenic inheritance.
Environmental effects on phenotype.

Correct Answer

A. Polygenic inheritance.

Explanation

A graph of phenotypic variation similar to the illustration strongly suggests polygenic inheritance. Polygenic inheritance occurs when multiple genes contribute to the expression of a single trait. This results in a continuous range of phenotypes, as seen in the graph. Incomplete dominance and codominance typically result in distinct phenotypic ratios, while epistasis involves the interaction of genes at different loci. Environmental effects on phenotype would result in more variation across different environments, rather than a continuous range of phenotypes.

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11.

The reason for the darker fur on the tail, ears, nose, and legs of a Siamese cat is

Incomplete dominance.
The activity of a heat-sensitive enzyme involved in melanin production.
Quantitative inheritence.
Epistasis.
The presence of different alleles for fur color in these regions.

Correct Answer

A. The activity of a heat-sensitive enzyme involved in melanin production.

Explanation

The darker fur on the tail, ears, nose, and legs of a Siamese cat is due to the activity of a heat-sensitive enzyme involved in melanin production. This enzyme is more active in cooler areas of the body, resulting in darker fur in those regions. This phenomenon is known as temperature-sensitive pigment expression.

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Bio Test 2 (Part 5)

Susan, a mother with type B blood, has a child with type O blood. She claims that Craig, who has type A blood, is the father. He claims that he cannot possibly be the father. Further blood tests ordered by the judge reveal that Craig is AA. The judge rules that

Quiz Preview

The rold of environmental factors on gene expression is illustrated by the

In cocker spaniels, black coat color (B) is dominant over red (b), and solid color (S) is dominant over spotted (s). If a solid red male is crossed with a solid black female to produce a red, spotted puppy, the genotypes of the parents (with male genotype first) will be

A color-blind man and a woman with normal vision whose father was color blind have a son. Color blindness, in this case, is caused by an X-linked recessive gene. If only the male offspring are considered, the probability that their son is color blind is

Genes that are located on the same chromosome

An autosomal recessive disorder

If a daughter expresses an X-linked recessive gene, she inherited the trait from

Genes at one locus that affect the expression of genes at a different locus are said to be

A graph of phenotypic variation similar to the illustration below strongly suggests

The reason for the darker fur on the tail, ears, nose, and legs of a Siamese cat is