Question 1

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.
  
Figure 14.2
-What is the likelihood that the progeny of IV-3 and IV-4 will have wooly hair?

Accepted Answer

IV-3 and IV-4 are both affected (shown by their open circles), which means they both carry at least one dominant allele for wooly hair. Therefore, there is a 50% chance that any progeny they have will inherit the dominant allele and exhibit the trait of wooly hair.

Question 2

Which describes the ability of a single gene to have multiple phenotypic effects?

Accepted Answer

Pleiotropy is the ability of a single gene to impact multiple phenotypic traits. This occurs because the gene product affects multiple pathways or processes in the cell. Examples of pleiotropic genes include sickle cell anemia, which affects both red blood cell shape and immune function, and Marfan syndrome, which affects both skeletal and cardiovascular development.

Question 3

A blue budgie is crossed with a white budgie. Which of the following results is not possible?

Accepted Answer

The answer of A blue budgie is crossed with a...

Question 4

Which of the following terms best describes when the phenotype of the heterozygote differs from the phenotypes of both homozygotes?

Accepted Answer

Incomplete dominance is the term used to describe when the phenotype of the heterozygote is a blend of the phenotypes of both homozygotes. This results in a third, intermediate phenotype that is different from both homozygous phenotypes.

Question 5

Which of the following is an example of polygenic inheritance?

Accepted Answer

Skin pigmentation in humans is an example of polygenic inheritance because it is controlled by multiple genes and influenced by environmental factors. This leads to a continuous range of skin colors rather than discrete categories.

Question 6

Which of the following provides an example of epistasis?

Accepted Answer

Epistasis occurs when the expression of one gene is affected by the expression of another gene. In rabbits, the genotype cc (homozygous recessive) prevents any fur color from developing, regardless of the genotype at other fur color genes. This is an example of epistasis because the expression of the fur color gene is dependent on the expression of the cc gene.

Question 7

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.
  
Figure 14.2
-What is the probability that individual III-1 is Ww?

Accepted Answer

The answer of The following questions refer to the pedigree...

Question 8

Huntington's disease is a dominant condition with late age of onset in humans. If one parent has the disease, what is the probability that his or her child will have the disease?

Accepted Answer

Huntington's disease is a dominant genetic disorder, which means that if one parent has the disease, each child has a 50% chance of inheriting the mutated gene and developing the disease, regardless of gender. Therefore, the probability of a child having the disease is 1/2 or 50%. Option C is the closest answer.

Question 9

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

Accepted Answer

Environmental factors such as soil pH can affect the color of hydrangea flowers. Soil with a pH below 6.0 results in blue flowers, while soil with a pH above 6.0 results in pink flowers. Therefore, the presence of different soil pH values in different areas of the flower garden can cause the plants to produce different colored flowers.

Question 10

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

Accepted Answer

Pleiotropy describes the phenomenon where a single gene affects multiple traits or functions. Cystic fibrosis is an example of pleiotropy because it affects various organs and systems in the body, resulting in a range of symptoms. Incomplete dominance, multiple alleles, and epistasis do not accurately describe the characteristics of cystic fibrosis.

Question 11

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-Which of the following is a possible phenotype for the father?

Accepted Answer

Since the mother is type A positive and the children have different blood types, we know that the mother must be heterozygous for blood type A. The daughter inherited an O allele from the mother and a positive allele from the father, meaning the father must be either AO or BO. The son inherited a B allele from the father and a negative allele from the mother, meaning the father must be BO. Therefore, the only possible phenotype for the father is B positive. The MN blood group information is irrelevant for determining the father's phenotype.

Question 12

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-Which of the following is a possible genotype for the mother?

Accepted Answer

Since the mother has blood type A, she must have at least one dominant allele for A (Iᴬ). Since her daughter is type O and her son is type B, she must also have a recessive allele for O (i) and a dominant allele for B (Iᴮ). The mother is Rh-positive, so she must have at least one dominant allele for Rh (R). For the MN blood group, we cannot determine the mother's genotype with the given information. 
Therefore, the only genotype that fits all of the given information is Iᴬi for the mother.

Question 13

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-Which of the following is a possible partial genotype for the son?

Accepted Answer

We know that the son is blood type B negative, which means he has the genotype Iᴮi. The ABO blood group is determined by three alleles: IA, IB, and i, with IA and IB being codominant and i being recessive. The mother must be heterozygous for A (IAi) to have a daughter with blood type O (ii), as O blood type is recessive. Therefore, the son must have inherited the Iᴮ allele from the father and the i allele from the mother. The MN blood group, on the other hand, is determined by codominant alleles, which means that both alleles are expressed in the phenotype. However, the question does not provide enough information to determine the son's MN genotype.

Question 14

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-Which of the following is the probable genotype for the mother?

Accepted Answer

The mother must have at least one dominant A allele because both her children have A blood type. However, she cannot have two dominant A alleles since her son's blood type is B. This means she must be heterozygous for the A allele, which is represented as Iᴬi. Since her daughter is O positive, the mother must also be Rh positive (Rr or RR). Therefore, the most probable genotype for the mother is IᴬiRr, which is choice D.

Question 15

Which describes the ABO blood group system?

Accepted Answer

The ABO blood group system is an example of multiple alleles, as there are three possible alleles (A, B, and O) that determine an individual's blood type.

Question 16

Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?

Accepted Answer

In this Punnett square, the offspring are listed across the top and left-hand side, and the potential gametes (sperm and egg) for each parent are listed in the rows and columns. Since we know the parents are both blue, we can assign them both the genotype "yyBB" (meaning they both have two copies of the recessive yellow gene and two copies of the dominant blue gene).

We can see that the only way to get white offspring is if both parents are carrying a copy of the recessive white gene, since white is a recessive trait that requires two copies of the "w" allele to be expressed. Therefore, we can assume that each parent has the genotype "yyBw" (meaning they have two copies of the recessive yellow gene and one copy of the dominant blue gene and one copy of the recessive white gene).

Using this information, we can fill out the Punnett square to see what combinations of gametes can be produced by each parent:

If we count up the possible genotypes for the offspring, we see that we get 3/16 with the genotype "yyBB" (meaning they have two copies of the recessive yellow gene and two copies of the dominant blue gene), 6/16 with the genotype "yyBw" (meaning they have two copies of the recessive yellow gene and one copy of the dominant blue gene and one copy of the recessive white gene), and 7/16 with the genotype "yybw" (meaning they have two copies of the recessive yellow gene and two copies of the recessive white gene).

Since we know that 5 of the 22 offspring were white, we can assume that they were all "yybw" (since that is the only genotype that expresses the white trait). We can then use the remaining offspring to calculate the ratio of "yyBB" to "yyBw" genotypes. If we add up the number of "yyBB" and "yyBw" offspring, we get 3 + 6 = 9, leaving 22 - 9 = 13 offspring with the genotype "yybw".

To find the ratio of "yyBB" to "yyBw" offspring, we can divide the number with "yyBB" by the total number of offspring: 3/22. We can do the same for "yyBw": 6/22. This simplifies to about 0.136 for "yyBB" and 0.273 for "yyBw". Since these values are roughly equal, it's impossible to say for certain which of the parents (if any) had the "BB" genotype or the "Bb" genotype. However, we can see that the most likely genotypes for the two blue budgies are "yyBb" and "yyBb" (choice C), since this would produce both "yyBB" and "yyBw" offspring in roughly equal proportions. Alternatively, "yyBB" and "yyBB" (choice A) would also be a possibility if we assume that one of the parents had the "BB" genotype and the other had two copies of the "B" allele.

Question 17

A woman has six sons. The chance that her next child will be a daughter is

Accepted Answer

The chance of having a girl is always 1/2 or 50%. This is because the gender of each child is an independent event and isn't influenced by the gender of previous children. So even though the woman has had six sons already, the chance of her next child being a girl is still 1/2.

Question 18

Most genes have many more than two alleles. However, which of the following is also True?

Accepted Answer

Even if a gene has many alleles, the phenotype may still only have two options (e.g. brown or blue eyes). Choice A is false because some alleles can be codominant or recessive. Choice B is not necessarily true, as some alleles may be neutral or beneficial. Choice C may be true for some genes, but not all. Choice E is not true for all genes, as some organisms can be heterozygous for multiple alleles without lethal effects.

Question 19

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle.
  
Figure 14.2
-What is the genotype of individual II-5?

Accepted Answer

The answer of The following questions refer to the pedigree...

Question 20

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-If both children are of blood group MM, which of the following is possible?

Accepted Answer

Since both children are of blood group MM, it means that both parents must have at least one M allele each. Therefore, choice A is possible, as each parent could be either M or MN. Choices B, C, D, and E are not necessarily true based on the information given.

Quiz 14: Mendel and the Gene Idea

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, wooly hair. Affected individuals are indicated by an open square or circle. Figure 14.2 -What is the likelihood that the progeny of IV-3 and IV-4 will have wooly hair?