Ch. 3 Basic Principles of Heredity

Why was the pea plant an ideal plant for Mendel to use?

simple traits that are easy to identify

In a cross between AaBbCc and AaBbcc, what proportion of the offspring would be expected to be A_bbcc? (A_ means AA or Aa.)

3/32

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an offspring with the AB phenotype from a cross of aabb × AABB?

1 (100%)

A space capsule crashes to earth with an alien life form aboard. Two creatures emerge from the capsule, one with green skin and one with yellow skin. The yellow creature soon gives birth to offspring fathered by the green creature, producing 12 green and 8 yellow offspring. Green skin in these diploid creatures is dominant to yellow skin. You are curious to find out if the number of offspring is significantly different from expected Mendelian ratios, so you perform a chi-square test. What is the chi-square value for this cross?

0.8

In animals, the inability to make the pigment melanin results in albinism, a recessive condition. Two unaffected parents, who have decided to have three children, have a first child that has albinism (genotype aa). What is the probability that the second and third children will also have albinism?

1/16

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a wrinkled, green seed in the F2?

1/16

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AABB zygote from a cross of AaBb × AaBb?

1/16

A couple has six daughters and is expecting a seventh child. What is the probability that this child will be a boy?

1/2

Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. The man has fathered a child with a woman that does not have freckles. What is the probability that their child has freckles?

1/2

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AABb individual?

1/2

If an AaBbccDd individual is crossed to an AaBbCcDD individual, what is the probability that the first offspring will be of AabbccDd genotype?

1/32

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AaBb individual?

1/4

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AaBb zygote from a cross of AaBb × AABB?

1/4

If two heterozygous Aa plants are crossed with each other, what will be the genotypic ratio found in the offspring?

1:2:1

A geneticist is conducting an experiment by making a testcross. She expects the offspring of the testcross to result in a 1:2:1 ratio. She wants to see if her data for the three phenotypic classes could be reasonably assumed to have deviated from the expected values by chance. How many degree(s) of freedom should she use when evaluating the chi-square goodness-of-fit test?

2

A phenotypically normal man has phenotypically normal parents but he has a sister who has cystic fibrosis caused by a recessive mutant allele. What is the probability that the man is heterozygous for the cystic fibrosis allele?

2/3

If both husband and wife are known to be heterozygous for the autosomal recessive condition of albinism, what is the probability that among their four children, three will be normal and one will have albinism?

27/64

In a cross between AaBbCcDdEe and AaBbccDdee, what proportion of the offspring would be expected to be A_bbC_ddE_? (A_ means AA or Aa.)

3/256

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a yellow seed in the F2?

3/4

In a cross between AABbCcDD and AaBbccdd, what proportion of the offspring would be expected to be A_B_C_D_? (A_ means AA or Aa.)

3/8

In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation?

50%

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a round, yellow seed in the F2?

9/16

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an offspring with the AB phenotype from a cross of AaBb × AaBb?

9/16

Which of the following statements is TRUE?

A testcross can be used to determine whether an individual is homozygous or heterozygous for a dominant allele.

A cross was made and a chi-square test was done to see if the results were consistent with the expected 1:1:1:1 ratio from this cross. Using p = 0.05 as the cutoff value, which of the following calculated chi-square values would be consistent with the deviations from the expected values being due to chance? (Select all that apply.)

A) 5.961 B) 0.536 C) 6.444 D) 2.384 E) 1.376

Which of the following crosses would produce a 3:1 ratio of phenotypes in the next generation?

Aa × Aa

Which of the following crosses would produce a 1:1 ratio of phenotypes in the next generation?

Aa × aa

In dogs, black coat color (B) is dominant over brown (b), and solid coat color (S) is dominant over white spotted coat (s). A cross between a black, solid female and a black, solid male produces only puppies with black, solid coats. This same female was then mated with a brown, spotted male. Half of the offspring from this cross were black and solid, and half of the offspring were black and spotted. What is the genotype of the female?

BBSs

In dogs, black coat color (B) is dominant over brown (b), and solid coat color (S) is dominant over white spotted coat (s). A cross between a black, solid female and a black, solid male produces only puppies with black, solid coats. This same female was then mated with a brown, spotted male. Have of the offspring from this cross were black and solid, and half of the offspring were black and spotted. Which of the following could be the genotype of the black, solid male?

BbSS

While doing fieldwork in Madagascar, you discover a new dragonfly species that has either red (R) or clear (r) wings. Initial crosses indicate that R is dominant to r. You perform three crosses using three different sets of red-winged parents with unknown genotype and observe the following data:

Cross Phenotypes 1 72 red-winged, 24 clear-winged 2 12 red-winged 3 96 red-winged crosses 2 and 3

Which of the following was NOT one of Mendel's conclusions based on his monohybrid crosses?

Genes are carried on chromosomes.

What important genetics concept is being shown in the diagram?

Mendel's principle of segregation

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A plant of unknown genotype is testcrossed to a true-breeding plant with wrinkled and green seeds. The offspring produced were 53 round and yellow, 49 round and green, 44 wrinkled and yellow, and 51 wrinkled and green. What is the likely genotype of the parent in question?

RrYy

Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. What is the genotype of the F1 progeny?

RrYy

Gregor Mendel carried out a cross between two pea plants by taking pollen from a plant that was homozygous for round seeds and dusting the pollen onto the stigma of a plant homozygous for wrinkled seeds. Which of the following would be the reciprocal cross that Mendel had carried out for this experiment?

Stigma of a plant homozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant

In poodles, black fur is dominant to white fur. A black poodle is crossed with a white poodle. In a litter of four, all of the puppies are black. What is the BEST conclusion?

The black poodle is probably homozygous.

Which statement(s) about probabilities is/are TRUE? (Select all that apply.)

The chi-square test is used to determine if observed outcomes are consistent with expected outcomes. Branched diagrams are used for determining probabilities of various phenotypes or genotypes for genetic crosses involving more than one gene pair. The probability of rolling an even number on a single roll of a six-sided die is 1/6+1/6+1/6.

An organism produces the gametes shown. Which statement about the meiotic divisions that produced these gametes (assume no crossing over) is TRUE?

The gametes shown could NOT have resulted from a single meiotic event with two divisions

In Labrador retrievers, black coat color is dominant to brown. Suppose that a black Lab is mated with a brown one and the offspring are four black puppies and one brown puppy. What can you conclude about the genotype of the black parent?

The genotype must be Bb.

Honeybees have a haplo-diploid sex determination system where females develop from a fertilized egg (they are diploid, having one allele from the female queen and one allele from the male), and males develop from unfertilized eggs (they are haploid, having only one allele from the queen). Assuming that the female parent (queen) is heterozygous for a particular gene, what is the probability that a female offspring will inherit the recessive allele from her mother? What is the probability that a male offspring will inherit a recessive allele from his mother?

The probability that a daughter will inherit a recessive allele from her mother is 50%; the probability that a son will inherit a recessive allele from his mother is 50%.

In a cross between pure-breeding tall plants with pure-breeding short plants performed by Mendel, all of the F1 are tall. When these plants are allowed to fertilize themselves, the F2 plants occur in a ratio of 3 tall to 1 short. Which of the following is NOT a valid conclusion from these results?

The tall and short traits assort independently of each other in this cross.

If an organism of genotype Aa was used for a testcross, what was the genotype of the other individual used in the cross?

aa

Genes come in different versions called:

alleles

In dogs, black coat color (B) is dominant over brown (b), and solid coat color (S) is dominant over white spotted coat (s). A cross between a black, solid female and a black, solid male produces only puppies with black, solid coats. This same female was then mated with a brown, spotted male. Half of the offspring from this cross were black and solid, and half of the offspring were black and spotted. What is the genotype of the brown, spotted male?

bbss

The ability to curl one's tongue into a U-shape is a genetic trait. Curlers always have at least one curler parent but noncurlers can have one or both parents who are curlers. Using C and c to symbolize the alleles that control this trait, what is the genotype of a noncurler?

cc

In Mendel's peas, purple flower color is dominant to white. From which of the following descriptions can you NOT infer the genotype completely?

purple

Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. What is the man's genotype?

heterozygous

The figure shows that independent assortment results from the segregation of chromosomes at anaphase I of meiosis. Assuming four functional products of meiosis and no crossing over, what is the minimum number of meiotic events (an event consisting of the two meiotic divisions) to produce the RY, Ry, rY, and ry gametes?

two