Question 1

Use the following pedigree (Figure 14.3) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis.
  
Figure 14.3
-From this pedigree, how does this trait seem to be inherited?

Accepted Answer

The trait of colon cancer in this family seems to be inherited as an autosomal dominant trait. This is because affected individuals (dark-shaded symbols) are present in multiple generations and have at least one affected parent. There is no evidence to suggest that the trait is inherited from mothers or as an autosomal recessive or incomplete dominant trait. There is also no evidence to suggest that epistasis plays a role in the inheritance of this trait.

Question 2

Use the following information to answer the questions below.
Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
-If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?

Accepted Answer

Since the genes for bent wings and vestigial wings are on different loci, mating homozygous bent wing flies with homozygous vestigial wing flies would result in offspring that are heterozygous for both traits, thus all +bt +vg heterozygotes.

Question 3

Use the following pedigree (Figure 14.3) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis.
  
Figure 14.3
-The affected woman in generation IV is thinking about her future and asks her oncologist (cancer specialist)whether she can know whether any or all of her children will have a high risk of the same cancer. The doctor would be expected to advise which of the following?
I.genetic counseling
II.prenatal diagnosis when/if she becomes pregnant
III.testing to see whether she has the allele
IV.testing to see whether her future spouse or partner has the allele

Accepted Answer

Genetic counseling can help the woman understand the risks of her children inheriting the gene mutation and what options are available. Prenatal diagnosis can help determine whether an unborn child has inherited the gene mutation. Testing the woman herself to see whether she has the allele is not necessary since she has already been diagnosed with colon cancer. Testing the future spouse or partner is also not necessary since the inheritance of the gene mutation is not dependent on the partner's genotype.

Question 4

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
-How many genes must be responsible for these coat colors in Labrador retrievers?

Accepted Answer

The inheritance of coat color in Labrador retrievers is determined by two genes: one gene controls the production of black pigment, and the other gene controls the production of brown pigment. The yellow color is a result of a modification in the expression of the genes that produce the black pigment. Therefore, the combination of alleles on these two genes determines the coat color of Labrador retrievers.

Question 5

Use the following information to answer the questions below.
Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
-If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are mated, what is the probability of offspring with bent wings only?

Accepted Answer

The probability of offspring with bent wings only is 3/16. This is calculated by considering the independent assortment of the two genes, each with a 3:1 ratio for the dominant to recessive phenotype. The probability of having bent wings (bt) and not vestigial wings (vg) is (1/4) for bt/bt and (3/4) for +/vg, resulting in (1/4) * (3/4) = 3/16.

Question 6

The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark 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 7

Use the following information to answer the questions below.
Skin color in a certain species of fish is inherited via a single gene with four different alleles.
-How many different types of gametes would be possible in this system?

Accepted Answer

The number of gametes possible in a system with n number of alleles is 2^n. In this case, there are 4 alleles, so the number of gametes possible is 2^4 = 16. However, since each gamete can only carry one allele, the actual number of different types of gametes will be equal to the number of alleles, which is 4.

Question 8

Use the following information to answer the questions below.
Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
-A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F₁ individuals?

Accepted Answer

The dwarf, red snapdragon is ttRr (dwarf=t and red=R). The plant homozygous for tallness and white flowers is TTRr (tall=T and white=r). 
The cross can be represented as follows:

T T R r   (gametes from homozygous tall plant)
t R t r    (gametes from dwarf, red plant)
––––––––––––––––––––––
TtRr     (tall and red)
Ttrr      (tall and white)
ttRr      (dwarf and pink)
ttrr       (dwarf and white)

Therefore, the genotype and phenotype of the F1 individuals are TtRr (tall and pink).

Question 9

Use the following information to answer the questions below.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
-The flower color trait in radishes is an example of which of the following?

Accepted Answer

The inheritance of flower color in radishes shows incomplete dominance, as the offspring of a cross between a red-flowered plant and a white-flowered plant have all-purple flowers. This indicates that neither the red allele nor the white allele is completely dominant over the other, resulting in a blending of colors. The other options (multiple allelic system, sex linkage, codominance, and epistasis) are not applicable to this scenario.

Question 10

Use the following information to answer the questions below.
Skin color in a certain species of fish is inherited via a single gene with four different alleles.
-One fish of this type has alleles 1 and 3 (S₁S₃)and its mate has alleles 2 and 4 (S₂S₄). If each allele confers a unit of color darkness such that S₁ has one unit, S₂ has two units, and so on, then what proportion of their offspring would be expected to have five units of color?

Accepted Answer

The answer of Use the following information to answer the...

Question 11

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
-In one type cross of black × black, the results were as follows:
9/16 black
4/16 yellow
3/16 brown
The genotype aabb must result in which of the following?

Accepted Answer

The genotype "aabb" results in yellow puppies, as indicated by the cross results where different combinations of alleles result in different coat colors. The presence of both recessive alleles "aa" and "bb" together is necessary to produce a yellow coat, as the dominant alleles for black and brown are not present.

Question 12

Use the following information to answer the questions below.
Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
-If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?

Accepted Answer

The genotype of the first parent is RrTt (heterozygous for both traits) and the genotype of the second parent is also RrTt.

The Punnett square for this cross is:

|   | RT | Rt | rT | rt |
|---|----|----|----|----|
| RT | RR TT | RR Tt | Rr TT | Rr Tt |
| Rt | RR tT | RR tt | Rr tT | Rr tt |
| rT | Rr TT | Rr Tt | rr TT | rr Tt |
| rt | Rr tT | Rr tt | rr tT | rr tt |

The resulting ratio is 6:3:3:2:1:1, which represents:

- 6 individuals with dominant height and color (RRTT, RRTt)
- 3 individuals with dominant height and recessive color (RRtt, RrtT)
- 3 individuals with recessive height and dominant color (rrTT, rrTt)
- 2 individuals with recessive height and color, but heterozygous for both traits (rrtt)
- 1 individual with dominant height and pink colored flowers (RrTT)
- 1 individual with dominant height and pink colored flowers (RrTt)

Therefore, the answer is B.

Question 13

Use the following information to answer the questions below.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
-If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F₁ will be expected to be which of the following?

Accepted Answer

The cross between true-breeding red long radishes and white oval radishes produces offspring that are all purple in color. This indicates that the white-flowered plant has a recessive allele for flower color (since it does not express the dominant red allele) and the red-flowered plant is homozygous dominant for flower color. The fact that all the F1 offspring are purple indicates that flower color is inherited in a simple dominant-recessive pattern. The F1 offspring are also all long because the long trait is dominant over the oval trait. Therefore, the expected F1 offspring would be purple and long (choice D).

Question 14

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

Accepted Answer

The likelihood depends on the genetic makeup of IV-3 and IV-4. If the trait is autosomal recessive and both parents are carriers, there is a 50% chance their child will inherit one recessive allele from each parent, thus expressing the trait.

Question 15

Use the following pedigree (Figure 14.3) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis.
  
Figure 14.3
-In each generation of this family after generation I, the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic)cases of this cancer (~ 63 years). What is the most likely reason?

Accepted Answer

Hereditary (or familial) cases of colon cancer typically occur at earlier ages than nonfamilial cases. This suggests that this family has an inherited genetic predisposition for colon cancer, which leads to earlier onset of the disease than in sporadic cases. The fact that this pattern is seen in every generation after the first also supports the idea of an inherited mutation. Option A is not a likely explanation because it does not explain the consistent pattern of early onset of colon cancer in this family. Option C is incorrect because the pattern of early onset is observed in this family and is not due to chance. Option D is possible, but the pedigree does not provide evidence for this explanation. Option E is not correct because colon cancer is not present at birth and typically takes many years to develop.

Question 16

Use the following pedigree (Figure 14.3) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis.
  
Figure 14.3
-What is the genotype of the deceased individual in generation II?

Accepted Answer

Since the individual in question is affected by colon cancer, they must have at least one copy of the cancer allele. Since their unaffected sibling inherited the non-cancer allele from both parents, the deceased individual must have inherited one cancer allele from one parent and one non-cancer allele from the other parent, making them heterozygous for the gene for colon cancer.

Question 17

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
-These results indicate which of the following?

Accepted Answer

The answer of Use the following information to answer the...

Question 18

Use the following information to answer the questions below.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
-In the F₂ generation of the above cross, which of the following phenotypic ratios would be expected?

Accepted Answer

The answer of Use the following information to answer the...

Question 19

Use the following information to answer the questions below.
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower color and location assort independently.
-Among the F₂ offspring, what is the probability of plants with white axial flowers?

Accepted Answer

The traits segregate independently, so we calculate the probability of each trait separately and then multiply them. For flower color, red (R) is dominant over white (r), and for flower location, axial (A) is dominant over terminal (a). The F₁ generation, all RrAa, produces gametes that combine in the F₂ generation. The probability of white flowers (rr) is 1/4, and the probability of axial flowers (A-) is 3/4 (AA or Aa). Multiplying these probabilities gives 1/4 * 3/4 = 3/16.

Question 20

Use the following information to answer the questions below.
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower color and location assort independently.
-If 1,000 F₂ offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?

Accepted Answer

Given that the genes for flower color and location assort independently and considering the Mendelian inheritance, we can determine the expected phenotypic ratio for the F2 generation. Since all F1 individuals have red, axial flowers, they are heterozygous for both traits (Rr, Ax). The traits segregate independently, so we use the product rule to find the probability of each phenotype. For red flowers (R), the probability is 3/4 (RR or Rr), and for terminal flowers (x), the probability is 1/4 (since axial (Ax) is dominant and terminal (x) is recessive). Multiplying these probabilities gives 3/4 * 1/4 = 3/16. Out of 1,000 offspring, 3/16 would be expected to have red, terminal flowers, which is approximately 187.5, rounding to the closest option gives 190.

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, W. Affected individuals are indicated by a dark square or circle. Figure 14.2 -What is the probability that individual III-1 is Ww?

Use the following information to answer the questions below. Skin color in a certain species of fish is inherited via a single gene with four different alleles. -How many different types of gametes would be possible in this system?

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