Question 1

A _____ square is a useful diagram to show the results of an F₁ × F₁ cross.

Accepted Answer

A Punnett square is specifically designed to show the results of a cross between two individuals and predict the probabilities of offspring genotypes and phenotypes.

Question 2

In pea plants, flowers are either white or purple; the purple color is produced by pigments called anthocyanins. The production of anthocyanins is a two-step process: the first is controlled by the C gene and the second by the P gene. Both genes must produce functional proteins for anthocyanin to be produced. For each gene, the dominant (C and P) alleles produce functional proteins. Which of the following genotypes will produce white (no pigment) flowers?

Accepted Answer

For anthocyanin to be produced, both the C and P genes must have at least one dominant allele. Genotypes ccPP and CCpp have at least one gene (C or P) completely recessive, meaning no functional protein for anthocyanin production is made, resulting in white flowers.

Question 3

If Mendel based his data only on two traits, and the genes influencing those traits were linked and located close together on the same chromosome, which of his laws would he NOT have been able to resolve?

Accepted Answer

Mendel would not have been able to resolve the law of independent assortment if the genes influencing the traits were located close together on the same chromosome because they would not have sorted independently during meiosis.

Question 4

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect the shape of the seed capsule in the broadleaf weed known as shepherd's purse. Each gene has two alleles, one of which is dominant for the shape of the seed capsule. Genotypes of the form A- B-, A- bb, and aa B- have triangular seed capsules, whereas the seed capsules of aa bb genotypes are ovoid. What ratio of triangular : ovoid is expected from the cross Aa Bb × Aa Bb?

Accepted Answer

The expected phenotypic ratio for a dihybrid cross Aa Bb × Aa Bb, where both genes show complete dominance and independent assortment, is 9:3:3:1. However, in this case, the genotypes A- B-, A- bb, and aa B- all result in triangular seed capsules, while only aa bb results in ovoid seed capsules. Therefore, the 9:3:3:1 ratio collapses into a 15:1 ratio of triangular to ovoid seed capsules.

Question 5

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect flower color in sweet peas. Each gene as two alleles, one of which is dominant for flower color. Genotypes of the form A- B- have purple flowers, whereas those of the form A- bb, aa B-, and aa bb have white flowers. What ratio of purple : white is expected from the cross Aa Bb × Aa Bb?

Accepted Answer

When we cross Aa Bb × Aa Bb, we can use a Punnett square to determine the possible genotypes and corresponding phenotypes of the offspring.

|   | A  | a  |
|---|---|---|
| B | AB  | aB |
| b | Ab | ab |

We can see that there are 9 possible genotypes that result in purple flowers and 7 possible genotypes that result in white flowers. Thus, the expected ratio of purple : white is 9:7.

Question 6

Two genes, C and I, which undergo independent assortment, affect feather color in leghorn chickens. Each gene has two alleles, one of which is dominant for feather color. The gene product of the dominant allele C is necessary for color in the feathers; however, the gene product of the dominant allele I is an inhibitor of color production in the feathers, even when C is present. What ratio of white feathers : colored feathers is expected among the progeny of the cross Cc Ii × Cc Ii?

Accepted Answer

In this genetic cross, the presence of the dominant allele I inhibits color production regardless of the C allele's presence. Therefore, to have colored feathers, a chicken must have at least one dominant C allele (for color) and be homozygous recessive for the I allele (ii) to not inhibit color. The cross Cc Ii × Cc Ii results in a 9:3:3:1 ratio for the four possible phenotypic combinations, but since three of these combinations result in white feathers due to the presence of the dominant I allele, only the combination where the genotype is ccii will result in colored feathers. This gives us a 13:3 ratio of white to colored feathers.

Question 7

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

Accepted Answer

The "3"s in the ratio refer to individuals that are dominant for one trait (either A or B) and recessive for the other trait (either a or b). This is because in the offspring of the cross between AA bb and aa BB, all individuals are heterozygous for both traits (Aa Bb). When these individuals undergo independent assortment, there are four possible gametes that can be produced with equal frequency: AB, Ab, aB, and ab. Therefore, in the F₂ generation, the ratio of phenotypes is 9 dominant for both traits : 3 dominant for one trait and recessive for the other : 3 recessive for one trait and dominant for the other : 1 recessive for both traits.

Question 8

Which of the following populations would you expect to have the MOST genetic diversity within the group?

Accepted Answer

A stock of tomato plants that is not true-breeding would have the most genetic diversity because it is not genetically uniform like the true-breeding stock (A), and it also has undergone some mixing of genetic material from the cross of two different true-breeding stocks (B).

Question 9

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, R- means the individual has either the genotype RR or Rr. In Duroc-Jersey pigs, genotypes R- S- have a red coat color, R- ss and rr S- have sandy-colored coats, and rr ss pigs are white. R and S show independent assortment. What is the ratio of red : sandy : white among progeny of the cross Rr Ss × Rr Ss?

Accepted Answer

The ratio of red (R- S-) : sandy (R- ss and rr S-) : white (rr ss) is 9:6:1.

Question 10

With independent assortment, the ratio of genotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

Accepted Answer

The "4" in the ratio refers to the genotype Aa Bb. This is the result of independent assortment of the two sets of alleles, with each having a 1/2 chance of being in the gamete. Therefore, the A and a alleles can be combined with equal probabilities to form the gametes, as can the B and b alleles. The genotype Aa Bb is produced when an Aa gamete combines with a Bb gamete, which occurs 4 times out of the total of 16 possible combinations in the F1 generation.

Question 11

With independent assortment, the ratio of genotypes in the F₂generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotypes do the "2s" in the ratio refer?

Accepted Answer

The "2s" in the ratio refer to individuals that are homozygous for one gene and heterozygous for the other, which occurs in three combinations in the given ratio.

Question 12

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, W- means the individual has either the genotype WW or Ww. In summer squash, genotypes W- G- and W- gg are white, ww G- are yellow, and ww gg are green. W and G show independent assortment. What is the ratio of white : yellow : green among progeny of the cross Ww Gg × Ww Gg?

Accepted Answer

The cross Ww Gg × Ww Gg can be analyzed by considering each gene separately and then combining the results. For the W gene, the cross Ww × Ww produces 3/4 W- (WW or Ww) and 1/4 ww. For the G gene, the cross Gg × Gg also produces 3/4 G- (GG or Gg) and 1/4 gg. Combining these, the ratio of white (W- G- and W- gg) to yellow (ww G-) to green (ww gg) is 9/16 white (3/4 W- × 3/4 G- plus 3/4 W- × 1/4 gg), 3/16 yellow (1/4 ww × 3/4 G-), and 1/16 green (1/4 ww × 1/4 gg), which simplifies to 12:3:1.

Question 13

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect fruit shape in summer squash. Each gene has two alleles, one of which is dominant for fruit shape. Genotypes of the form A- B- have disc-shaped fruit, those of the form A- bb and aa B- have sphere-shaped fruit, and genotype aa bb has long fruit. What ratio of disc : sphere : long is expected from the cross Aa Bb × Aa Bb?

Accepted Answer

The cross Aa Bb × Aa Bb involves two genes that assort independently, leading to a 9:3:3:1 phenotypic ratio for a dihybrid cross. However, because both A- B- leads to disc-shaped fruit, A- bb and aa B- lead to sphere-shaped fruit, and aa bb leads to long fruit, the phenotypic ratio translates to 9 disc (A- B-), 6 sphere (3 from A- bb + 3 from aa B-), and 1 long (aa bb), resulting in a 9:6:1 ratio.

Question 14

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect coat color in the house mouse. Each gene has two alleles, one of which is dominant for coat color. Genotypes of the form A- B- have a brownish color called agouti, those of the form A- bb are black, and those of the form aa B- and aa bb are albino (white). What ratio of agouti : black : white is expected from the cross Aa Bb × Aa Bb?

Accepted Answer

To solve this problem, we can use a Punnett square. 
```
  | A  a
--|-----
B-|AB AB
b-|Ab Ab
```
When we cross Aa Bb × Aa Bb, we get the following genotypic ratio: 
- 1 AA BB (agouti)
- 2 Aa BB (agouti)
- 1 aa BB (white)
- 2 AA Bb (agouti)
- 4 Aa Bb (agouti)
- 2 aa Bb (black)
- 1 AA bb (black)
- 2 Aa bb (black)
- 1 aa bb (white)

To get the phenotypic ratio, we can group together the individuals with the same coat color: 
- Agouti: 1+2+2 = 5
- Black: 2+4+2 = 8
- White: 1+1 = 2

Therefore, the ratio of agouti : black : white is 5:8:2, which simplifies to 9:3:4. The answer is B.

Question 15

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, R- means the individual has either the genotype RR or Rr. In Duroc-Jersey pigs, genotypes R- S- have a red coat color, R- ss and rr S- have sandy-colored coats, and rr ss pigs are white. R and S show independent assortment. What cross is expected to result in all sandy-colored progeny?

Accepted Answer

The answer of In genetics, the dash symbol (-) is...

Question 16

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, W- means the individual has either the genotype WW or Ww. In summer squash, genotypes W- G- and W- gg are white, ww G- are yellow, and ww gg are green. W and G show independent assortment. What cross would yield white and yellow progeny in the ratio of 1:1?

Accepted Answer

To obtain a 1:1 ratio of white and yellow progeny, we need to cross a white (W- G- or W- gg) with a yellow (ww G-). The only option that will give us this type of cross is E) Ww Gg × ww GG. The heterozygous Ww and Gg parent will have a 50% chance of passing on the dominant W and G alleles, resulting in white progeny, and a 50% chance of passing on the recessive w and G alleles, resulting in yellow progeny.

Question 17

In humans, ability to roll the tongue (R) is dominant to being unable to roll (r). Having freckles (F) is dominant to having no freckles (f). A freckled tongue-roller could have which of the following genotypes?

Accepted Answer

A freckled tongue-roller could have the genotypes RRFF or RrFf because both combinations include at least one dominant allele for tongue rolling (R) and at least one dominant allele for having freckles (F), which are necessary to express these traits.

Question 18

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype does the "9" in the ratio refer?

Accepted Answer

The 9 in the ratio refers to the phenotype that is dominant for both traits (AA BB). This is because when two true-breeding parents with different homozygous genotypes for two traits are crossed, the F1 generation will be heterozygous for both traits, and in the F2 generation, the dominant phenotype for both traits will appear in a 9:3:3:1 ratio due to independent assortment of alleles.

Question 19

Suppose that, in humans, ability to roll the tongue (R) is dominant to being unable to roll (r), and having freckles (F) is dominant to having no freckles (f). If a woman heterozygous for both traits married a man with no freckles who couldn't roll his tongue, what is the probability that they would have a freckled, tongue-rolling child?

Accepted Answer

The woman's genotype is RrFf, and the man's genotype is rrff. To have a child with both freckles and the ability to roll their tongue (R_F_), the child must inherit an R from the mother (a 1/2 chance) and an F from the mother (also a 1/2 chance), while the alleles from the father (r and f) are given. Multiplying these probabilities gives 1/2 * 1/2 = 1/4.

Question 20

A Punnett square can be used to interpret the results of a testcross.

Accepted Answer

A Punnett square can be used to predict the outcomes of a testcross, which is a cross between an individual with an unknown genotype and an individual with a homozygous recessive genotype. The Punnett square helps to determine the probability of different genotypes and phenotypes in the offspring.

Quiz 16: Mendelian Inheritance

A _____ square is a useful diagram to show the results of an F₁ × F₁ cross.

If Mendel based his data only on two traits, and the genes influencing those traits were linked and located close together on the same chromosome, which of his laws would he NOT have been able to resolve?

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

Which of the following populations would you expect to have the MOST genetic diversity within the group?

With independent assortment, the ratio of genotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

With independent assortment, the ratio of genotypes in the F₂generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotypes do the "2s" in the ratio refer?

In humans, ability to roll the tongue (R) is dominant to being unable to roll (r) . Having freckles (F) is dominant to having no freckles (f) . A freckled tongue-roller could have which of the following genotypes?

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype does the "9" in the ratio refer?

A Punnett square can be used to interpret the results of a testcross.

Quiz 16: Mendelian Inheritance

A _____ square is a useful diagram to show the results of an F1 × F1 cross.

If Mendel based his data only on two traits, and the genes influencing those traits were linked and located close together on the same chromosome, which of his laws would he NOT have been able to resolve?

With independent assortment, the ratio of phenotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

Which of the following populations would you expect to have the MOST genetic diversity within the group?

With independent assortment, the ratio of genotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

With independent assortment, the ratio of genotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotypes do the "2s" in the ratio refer?

In humans, ability to roll the tongue (R) is dominant to being unable to roll (r) . Having freckles (F) is dominant to having no freckles (f) . A freckled tongue-roller could have which of the following genotypes?

With independent assortment, the ratio of phenotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype does the "9" in the ratio refer?

A Punnett square can be used to interpret the results of a testcross.

A _____ square is a useful diagram to show the results of an F₁ × F₁ cross.

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

With independent assortment, the ratio of genotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

With independent assortment, the ratio of genotypes in the F₂generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotypes do the "2s" in the ratio refer?

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype does the "9" in the ratio refer?