Question 1

A couple are both heterozygous for the dominant allele for polydactyly. They want to have three children. What is the probability that all three children will have polydactyly?

Accepted Answer

The probability that a child will have polydactyly when both parents are heterozygous is 3/4. For three children, the probability is (3/4)^3 = 27/64.

Question 2

The different alleles in human blood type are a demonstration of ____.

Accepted Answer

Human blood types demonstrate both dominance and codominance. The A and B alleles are codominant to each other but dominant over the O allele.

Question 3

You have type A blood (genotype I^Ai ). Who can you donate blood to in an emergency?

Accepted Answer

Individuals with type A blood can donate to others with the same blood type (A) and those with type AB, as AB individuals can receive blood from any ABO type due to the absence of anti-A and anti-B antibodies.

Question 4

Your mother has albinism, which is a recessive trait. Your father has cystic fibrosis, which is also a recessive trait. You discover that your new father-in-law has albinism and cystic fibrosis. If neither you nor your spouse has either albinism or cystic fibrosis, what are the odds that your first child will have either albinism or cystic fibrosis, but not both?

Accepted Answer

Since albinism and cystic fibrosis are both recessive traits, you and your spouse are carriers of both genes. The probability of your child inheriting one of these conditions (but not both) is calculated by adding the probability of inheriting albinism without cystic fibrosis to the probability of inheriting cystic fibrosis without albinism. Each parent has a 1/2 chance of passing on the recessive gene for each condition. The probability for one condition (e.g., albinism) without the other (cystic fibrosis) is (1/2 * 1/2) * (1/2 * 1/2) = 1/16 for albinism without cystic fibrosis and 1/16 for cystic fibrosis without albinism. Adding these probabilities gives 1/16 + 1/16 = 1/8. However, this calculation overlooks the scenario where the child inherits one condition from one parent and the other condition from the other parent, which also has a probability of 1/16. Therefore, the total probability is 1/8 (for one condition without the other) + 1/16 (for inheriting one condition from one parent and the other condition from the other parent) = 3/16. The correct calculation for the probability of inheriting either condition but not both should consider the combinations of inheriting one condition from one parent and not the other condition from either parent, leading to a probability of 3/8 when correctly accounting for all possible combinations.

Question 5

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown), and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what will result from a F₁cross between two mice?

Accepted Answer

In this scenario, the presence of homozygous recessive d alleles (dd) is epistatic to the B and b alleles, meaning it can mask their effects and result in white mice regardless of the B/b allele combination. Assuming both parents are heterozygous for both genes (BbDd), a Punnett square analysis shows that 9/16 of the offspring will have at least one D allele and one B allele (black), 3/16 will have at least one D allele and be homozygous for b (brown), and 4/16 will be homozygous for d (dd) and thus white, regardless of the B/b alleles.

Question 6

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. Which two plants would you cross to produce a true-breeding pink snapdragon?

Accepted Answer

True-breeding pink snapdragons cannot be created through crossing because the pink phenotype results from the heterozygous condition (one red allele and one white allele), which does not breed true.

Question 7

Your mother has albinism, which is a recessive trait. You learn that your spouse's mother also has albinism. Neither you nor your spouse have albinism. What are the odds that your first child will have albinism?

Accepted Answer

Since albinism is a recessive trait, both your mother and your spouse's mother being albino means you and your spouse are carriers (heterozygous). When two carriers have a child, the odds of the child being albino (receiving two recessive alleles) are 1/4.

Question 8

Your father has type B blood, and your mother has type O blood. You learn that you also have blood type O. What does this tell you?

Accepted Answer

Since you have type O blood and your mother has type O blood, it is clear that your mother's genotype must be ii, as type O blood is recessive and requires two i alleles. Your father, with type B blood, must carry at least one B allele. However, since you have type O blood, your father must also carry an i allele to pass on to you, making his genotype IBi (simplified here for clarity, not using the complex notation provided in the options). Option C correctly identifies your mother's genotype as ii, and while it attempts to provide a detailed genotype for your father, the specific notation it uses (I^Bi) is not standard and seems to be a placeholder for the concept that he carries one allele for type B blood and one for type O.

Question 9

If a monohybrid cross results in 1:2:1 genotypic and phenotypic ratios in the offspring, then which type of inheritance might be at work?

Accepted Answer

Incomplete dominance results in a 1:2:1 ratio for both genotypic and phenotypic outcomes because the heterozygous phenotype is a blend of the two homozygous phenotypes, rather than one completely dominating over the other.

Question 10

If a woman has blood type O and a man has blood type AB, what is the probability that they will have a child with blood type O?

Accepted Answer

A woman with blood type O can only pass on an O allele, and a man with blood type AB can pass on either an A or a B allele, but not an O allele. Therefore, it is impossible for them to have a child with blood type O, which would require two O alleles.

Question 11

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. If you cross a pink snapdragon ( C^RC^W) with a white snapdragon ( C^WC^W), what percentage of the progeny will be red?

Accepted Answer

The answer of In snapdragons, the red allele C^Ris incompletely...

Question 12

Your mother has albinism, which is a recessive trait. Your father has cystic fibrosis, which is also a recessive trait. You discover that your new father-in-law has albinism and cystic fibrosis. If neither you nor your spouse has either albinism or cystic fibrosis, what are the odds that your first child will have neither albinism nor cystic fibrosis?

Accepted Answer

Since albinism and cystic fibrosis are both recessive traits, you and your spouse are carriers of both genes. The probability that your child will not inherit either condition is 3/4 (for not having albinism) * 3/4 (for not having cystic fibrosis) = 9/16.

Question 13

Your mother has albinism, which is a recessive trait. Your father has cystic fibrosis, which is also a recessive trait. You discover that your new father-in-law has albinism and cystic fibrosis. If neither you nor your spouse has either albinism or cystic fibrosis, what are the odds that your first child will have both albinism and cystic fibrosis?

Accepted Answer

Since albinism and cystic fibrosis are both recessive traits, you and your spouse must be carriers of both traits (heterozygous) because each of your parents has one of these conditions. The probability of your child inheriting one recessive allele for albinism from both parents is 1/4, and the same goes for cystic fibrosis. Multiplying these probabilities (1/4 for albinism * 1/4 for cystic fibrosis) gives 1/16, indicating the chance of your child having both conditions.

Question 14

You have type O blood (genotype ii ). Who can you donate blood to in an emergency?

Accepted Answer

Individuals with type O blood (genotype ii) are considered universal donors because their blood can be donated to recipients of any ABO blood type (A, B, AB, or O) without causing adverse reactions related to ABO blood group incompatibility. This is because type O blood lacks both A and B antigens on the red blood cells, preventing the immune response that would occur if these antigens were present and recognized as foreign by the recipient's immune system.

Question 15

What is the key difference between incomplete dominance and codominance?

Accepted Answer

In incomplete dominance, the phenotype is a blend of the two alleles, whereas in codominance, both alleles are fully expressed and observable in the phenotype.

Question 16

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown), and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what genotype(s) result in a white mouse (no pigment)?

Accepted Answer

The presence of homozygous recessive dd genotype is necessary for a mouse to be white, regardless of the B allele configuration. This is because the d allele is epistatic to both B and b alleles, meaning it can mask their effects when in the homozygous recessive form. Therefore, both BBdd and Bbdd genotypes result in a white mouse.

Question 17

A man and woman are each heterozygous for the autosomal recessive gene for albinism. They already have two non-albino children and want to have two more. What is the probability that their next two children will be phenotypically identical to each other with regard to skin color (i.e., either both albino or neither albino)?

Accepted Answer

The answer of A man and woman are each heterozygous...

Question 18

A plant of genotype CCdd is crossed to a plant of genotype ccDD; the F₁offspring are then testcrossed to a ccdd plant. If the genes are on different chromosomes, what percentage of the offspring will be ccdd ?

Accepted Answer

25% of the offspring will be ccdd. In the initial cross (CCdd x ccDD), all F1 offspring will be heterozygous (CcDd) for both traits since the genes are on different chromosomes and assort independently. When these F1 offspring (CcDd) are testcrossed with a ccdd plant, the offspring will show all possible combinations of the two genes due to independent assortment, resulting in a 1:1:1:1 ratio of genotypes (CcDd, Ccdd, ccDd, ccdd). Therefore, 25% of the offspring will have the ccdd genotype.

Question 19

In ____, genes at one locus mask the effect of genes at another locus.

Accepted Answer

Epistasis occurs when the action of one gene is modified or completely masked by one or more other genes, which are often located at different loci on the chromosome.

Question 20

Two snapdragons heterozygous for alleles that encode red and white flower color are crossed. If the red and white alleles show incomplete dominance, what will be the ratios of phenotypes in the offspring?

Accepted Answer

In incomplete dominance, the heterozygous phenotype is intermediate between the two homozygous phenotypes. Crossing two heterozygous (Rr) snapdragons (where R = red and r = white) results in a 1:2:1 ratio of phenotypes: 25% RR (red), 50% Rr (pink), and 25% rr (white).

Quiz 12: Mendel, Genes, and Inheritance

A couple are both heterozygous for the dominant allele for polydactyly. They want to have three children. What is the probability that all three children will have polydactyly?

The different alleles in human blood type are a demonstration of ____.

You have type A blood (genotype I^Ai ) . Who can you donate blood to in an emergency?

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown) , and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what will result from a F₁cross between two mice?

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. Which two plants would you cross to produce a true-breeding pink snapdragon?

Your mother has albinism, which is a recessive trait. You learn that your spouse's mother also has albinism. Neither you nor your spouse have albinism. What are the odds that your first child will have albinism?

Your father has type B blood, and your mother has type O blood. You learn that you also have blood type O. What does this tell you?

If a monohybrid cross results in 1:2:1 genotypic and phenotypic ratios in the offspring, then which type of inheritance might be at work?

If a woman has blood type O and a man has blood type AB, what is the probability that they will have a child with blood type O?

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. If you cross a pink snapdragon ( C^RC^W) with a white snapdragon ( C^WC^W) , what percentage of the progeny will be red?

You have type O blood (genotype ii ) . Who can you donate blood to in an emergency?

What is the key difference between incomplete dominance and codominance?

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown) , and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what genotype(s) result in a white mouse (no pigment) ?

A plant of genotype CCdd is crossed to a plant of genotype ccDD; the F₁offspring are then testcrossed to a ccdd plant. If the genes are on different chromosomes, what percentage of the offspring will be ccdd ?

In ____, genes at one locus mask the effect of genes at another locus.

Two snapdragons heterozygous for alleles that encode red and white flower color are crossed. If the red and white alleles show incomplete dominance, what will be the ratios of phenotypes in the offspring?

Quiz 12: Mendel, Genes, and Inheritance

A couple are both heterozygous for the dominant allele for polydactyly. They want to have three children. What is the probability that all three children will have polydactyly?

The different alleles in human blood type are a demonstration of ____.

You have type A blood (genotype IAi ) . Who can you donate blood to in an emergency?

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown) , and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what will result from a F1cross between two mice?

In snapdragons, the red allele CRis incompletely dominant over the white allele CW. Which two plants would you cross to produce a true-breeding pink snapdragon?

Your mother has albinism, which is a recessive trait. You learn that your spouse's mother also has albinism. Neither you nor your spouse have albinism. What are the odds that your first child will have albinism?

Your father has type B blood, and your mother has type O blood. You learn that you also have blood type O. What does this tell you?

If a monohybrid cross results in 1:2:1 genotypic and phenotypic ratios in the offspring, then which type of inheritance might be at work?

If a woman has blood type O and a man has blood type AB, what is the probability that they will have a child with blood type O?

In snapdragons, the red allele CRis incompletely dominant over the white allele CW. If you cross a pink snapdragon ( CRCW) with a white snapdragon ( CWCW) , what percentage of the progeny will be red?

You have type O blood (genotype ii ) . Who can you donate blood to in an emergency?

What is the key difference between incomplete dominance and codominance?

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown) , and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what genotype(s) result in a white mouse (no pigment) ?

A plant of genotype CCdd is crossed to a plant of genotype ccDD; the F1offspring are then testcrossed to a ccdd plant. If the genes are on different chromosomes, what percentage of the offspring will be ccdd ?

In ____, genes at one locus mask the effect of genes at another locus.

Two snapdragons heterozygous for alleles that encode red and white flower color are crossed. If the red and white alleles show incomplete dominance, what will be the ratios of phenotypes in the offspring?

You have type A blood (genotype I^Ai ) . Who can you donate blood to in an emergency?

Mouse pigmentation is subject to epistasis of the B alleles by the d alleles. B (black) is dominant over b (brown) , and D is dominant over d . Homozygous d is epistatic to the black and brown genes. Given this information, what will result from a F₁cross between two mice?

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. Which two plants would you cross to produce a true-breeding pink snapdragon?

In snapdragons, the red allele C^Ris incompletely dominant over the white allele C^W. If you cross a pink snapdragon ( C^RC^W) with a white snapdragon ( C^WC^W) , what percentage of the progeny will be red?

A plant of genotype CCdd is crossed to a plant of genotype ccDD; the F₁offspring are then testcrossed to a ccdd plant. If the genes are on different chromosomes, what percentage of the offspring will be ccdd ?