Question 1

A couple has four children. What is the probability that they have four boys?

Accepted Answer

The probability of having a boy or a girl for each child is 1/2. For four children, the probability of all being boys is (1/2)^4 = 1/16.

Question 2

The gene L determines hair length in rabbits. The gene B determines hair color. A rabbit with long, black hair is crossed to a rabbit with short, white hair. All the offspring have long, black hair. What are the genotypes of the parents?

Accepted Answer

The offspring all have long, black hair, indicating that both traits (long hair and black color) are dominant and that each parent must have contributed a dominant allele for these traits. Since all offspring show the dominant phenotypes, the parents must be homozygous for these traits, making the only possible genotypes LLBB (for long, black hair) and llbb (for short, white hair).

Question 3

By convention, when an OBSERVED experimental outcome has a probability of occurrence of less than 5% (<0.05), the experimental results are considered to be _______.

Accepted Answer

When an observed experimental outcome has a probability of occurrence of less than 5% (<0.05), it is considered to be statistically significant and different from the expected outcome. This threshold is a common convention in statistical hypothesis testing for rejecting the null hypothesis.

Question 4

The statistical interpretation of a chi- square value is determined by identifying the________ .

Accepted Answer

The answer of The statistical interpretation of a chi- square...

Question 5

In peas, the yellow allele is dominant over the green allele. A plant with yellow peas was crossed to a plant with green peas. The resulting plants were 50% yellow and 50% green. What are the genotypes of the parents in this cross?

Accepted Answer

The parent with yellow peas must be heterozygous (Yy) because the offspring include both yellow and green peas, indicating that a recessive allele (y) was contributed by the yellow parent. The green parent must be homozygous recessive (yy) because green is a recessive trait.

Question 6

What phenotypic ratio would you expect as a result of a test cross between two individuals where one that is homozygous recessive for alleles at two independent loci?

Accepted Answer

A test cross involves crossing an individual with a homozygous recessive individual. When both individuals are homozygous recessive for two independent loci, all offspring will receive one recessive allele for each locus from each parent, resulting in a uniform phenotype ratio of 1:1:1:1, reflecting the combination of the two loci's alleles.

Question 7

If a plant with purple, axial flowers and green, inflated pods is heterozygous for all four genes, how many different types of gametes can it produce?

Accepted Answer

A heterozygous plant for four genes can produce 2^4 = 16 different types of gametes, as each gene can contribute two alleles.

Question 8

Humans have a gene, T, that is involved in muscle formation of the tongue. Individuals homozygous for one allele can roll their tongues, while individuals homozygous for the other allele cannot. If both parents can roll their tongues, but their child cannot, what can be said about the mode of inheritance?

Accepted Answer

Tongue rolling is a dominant trait, and for both parents to be able to roll their tongues but produce a child who cannot, they must both be heterozygous. This means they each carry one allele for tongue rolling and one allele for not being able to roll the tongue. The child inherited the non-rolling allele from each parent.

Question 9

Assuming independent assortment, what phenotypic ratio would you expect to see if an individual with the genotype RrGg is self- crossed?

Accepted Answer

The genotype RrGg self-crossed involves two traits, each with heterozygous alleles (Rr and Gg), leading to a 9:3:3:1 phenotypic ratio according to Mendelian genetics principles of independent assortment.

Question 10

In peas, axial (A) flower position is dominant to terminal (a), and tall (L) is dominant to short (l). If a plant that is heterozygous for both traits is allowed to self- fertilize, how many of the offspring would also be heterozygous for both traits?

Accepted Answer

The answer of In peas, axial (A) flower position is...

Question 11

What genotypic ratio would you expect to observe among the progeny of a monohybrid cross?

Accepted Answer

In a monohybrid cross, where one trait is being observed, the genotypic ratio among the progeny is typically 1:2:1. This ratio represents one homozygous dominant genotype, two heterozygous genotypes, and one homozygous recessive genotype.

Question 12

The P value is a quantitative expression of the probability that the results of another experiment of the same size and structure will DEVIATE FROM EXPECTED RESULTS AS MUCH AS OR MORE THAN BY CHANCE. The greater the difference between observed and expected results of an experiment,_________ .

Accepted Answer

The greater the difference between observed and expected results, the greater the chi-square (ç2) value, indicating a stronger deviation from what was expected. A higher ç2 value typically results in a lower P value, suggesting that the observed results are less likely to have occurred by chance alone.

Question 13

Genetic crosses in which F1 plants heterozygous for a given allele are crossed to generate a 3:1 phenotypic ratio in the F2 generation are known as _____.

Accepted Answer

Monohybrid crosses involve the crossing of F1 plants that are heterozygous for a single trait, leading to a 3:1 phenotypic ratio in the F2 generation.

Question 14

In rabbits, long hair and black fur are produced by the dominant alleles L and B, which assort independently. The genotype ll produces short hair and the genotype bb produces white fur. A cross between a male with short, black fur and a female with long, white fur produces four offspring with short, black fur, four offspring with long, white fur, four offspring with short, white fur, and four offspring with long, black fur. What are the genotypes of the parents?

Accepted Answer

The parents must be heterozygous for one trait and homozygous for the other to produce the observed 1:1:1:1 ratio of phenotypes in their offspring. The male with short, black fur must be llBb, and the female with long, white fur must be Llbb.

Question 15

In peas, the smooth allele is dominant over the wrinkled allele. A plant with round peas was crossed to a plant with wrinkled peas and all of the resulting plants had smooth peas. What are the genotypes of the parents in this cross?

Accepted Answer

Since all offspring have smooth peas, one parent must have two dominant alleles (RR) and the other must be homozygous recessive (rr) to only pass on the wrinkled allele.

Question 16

In peas, axial (A) flower position is dominant to terminal (a), tall (L) is dominant to short (l), and yellow (Y) is dominant to green (y). If a plant that is heterozygous for all three traits is allowed to self- fertilize, how many of the offspring would show the dominant phenotype for all three traits?

Accepted Answer

The plant in question is heterozygous for all three traits, meaning its genotype is AaLlYy. When it self-fertilizes, the offspring genotypes can be predicted using a Punnett square. For each trait, the heterozygous condition (Aa, Ll, Yy) results in a 3:1 ratio of dominant to recessive phenotypes. When considering all three traits together, the probability of an offspring displaying all dominant phenotypes is (3/4) * (3/4) * (3/4) = 27/64.

Question 17

You count 1000 F2 seeds from a monohybrid cross. How many seeds do you expect to display the dominant phenotype?

Accepted Answer

In a monohybrid cross, the expected phenotypic ratio in the F2 generation is 3:1 for dominant to recessive traits. Therefore, out of 1000 seeds, 750 are expected to display the dominant phenotype.

Question 18

In Guinea pigs, short hair (S) is dominant over long hair (s), rough coat (R) is dominant over smooth coat (r), and black hair (B) is dominant over white hair (b). Which of the following individuals could produce these (and only these) four possible gametes: SRb, Srb, sRb, srb.

Accepted Answer

The answer of In Guinea pigs, short hair (S) is...

Question 19

In mice, black coat color is dominant to white coat color. In the pedigree below, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols.  What is the probability that I- 1, I- 2, II- 2, AND III- 1 are all heterozygous?

Accepted Answer

The answer of In mice, black coat color is dominant...

Question 20

In mice, black coat color is dominant to white coat color. In the pedigree below, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols.  What is the genotype of III- 1?

Accepted Answer

The answer of In mice, black coat color is dominant...

Quiz 2: Transmission Genetics