Deck 3: Basic Principles of Heredity

Question 1

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?

A) 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%.
B) 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 100%.
C) The probability that a daughter will inherit a recessive allele from her mother is 100%; the probability that a son will inherit a recessive allele from his mother is 50%.
D) The probability that a daughter will inherit a recessive allele from her mother is 100%; the probability that a son will inherit a recessive allele from his mother is 100%.
E) The probability that a daughter will inherit a recessive allele from her mother is 0%; the probability that a son will inherit a recessive allele from his mother is 100%.

Answer 1

A

Question 2

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

A) generation time that is several years
B) simple traits that are easy to identify
C) low numbers of offspring produced
D) expensive and time-consuming to grow
E) All of the answers are correct.

Answer 2

B

Question 3

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?

A) The black poodle is definitely homozygous.
B) The black poodle is probably homozygous.
C) The black poodle is definitely heterozygous.
D) The black poodle is probably heterozygous.
E) The genotype of the black poodle cannot be inferred with this information.

Answer 3

B

Question 4

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?

A) Stigma of a plant homozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant
B) Stigma of a plant homozygous for round seed pollinated with pollen from a plant heterozygous for wrinkled-seed plant
C) Stigma of a plant heterozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant
D) Stigma of a plant homozygous for wrinkled seed pollinated with pollen from a plant homozygous for round-seed plant
E) Stigma of a plant homozygous for wrinkled seed pollinated with pollen from a plant homozygous for wrinkled-seed plant

Question 5

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

A) AA × AA
B) AA × aa
C) Aa × Aa
D) Aa × aa
E) aa × aa

Question 6

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?

A) The allele that produces the tall condition is dominant to the allele that produces the short condition.
B) The difference between tall and short stature in these lines is controlled by a single gene pair.
C) During production of gametes in F₁ plants, the tall and short alleles segregate from each other equally into the gametes.
D) The tall and short traits assort independently of each other in this cross.
E) Fertilization occurs randomly between gametes carrying the tall and short alleles.

Question 7

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

A) AA × AA
B) AA × aa
C) Aa × Aa
D) Aa × aa
E) aa × aa

Question 8

Which of the following statements is TRUE?

A) The genotype is the physical appearance of a trait.
B) Alleles, genes, and loci are different names for the same thing.
C) The phenotype of a dominant allele is never seen in the F₁ progeny of a monohybrid cross.
D) A testcross can be used to determine whether an individual is homozygous or heterozygous for a dominant allele.

Question 9

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

A) Genes are carried on chromosomes.
B) Alleles exist in pairs.
C) Alleles segregate equally into gametes.
D) Alleles behave as particles during inheritance.
E) One allele can mask the expression of the other allele.

Question 10

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?

A) 1/4
B) 1/3
C) 1/2
D) 2/3
E) 3/4

Question 11

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 12

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?

A) The genotype must be BB.
B) The genotype must be bb.
C) The genotype must be Bb.
D) The genotype could be either BB or Bb.
E) The genotype cannot be determined from these data.

Question 13

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?

A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Question 14

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

A) The probability of a woman giving birth to three girls in a row is 1/2+1/2+1/2.
B) The chi-square test is used to determine if observed outcomes are consistent with expected outcomes.
C) The probability of two or more independent events occurring together is calculated by adding their independent probabilities.
D) Branched diagrams are used for determining probabilities of various phenotypes or genotypes for genetic crosses involving more than one gene pair.
E) The probability of rolling an even number on a single roll of a six-sided die is 1/6+1/6+1/6.

Question 15

Genes come in different versions called:

A) alleles.
B) loci.
C) genotypes.
D) chromosomes.
E) genomes.

Question 16

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?

A) homozygous dominant
B) homozygous recessive
C) heterozygous
D) heterologous
E) homologous

Question 17

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: $$\begin{array} { | l | l | } \hline \text { Cross } & \text { Phenotypes } \\\hline 1 & 72 \text { red-winged, } 24 \text { clear-winged } \\\hline 2 & 12 \text { red-winged } \\\hline 3 & 96 \text { red-winged } \\\hline\end{array}$$ Which cross is likely to have at least one parent with the genotype RR?

A) cross 1
B) cross 2
C) cross 3
D) crosses 1 and 2
E) crosses 2 and 3

Question 18

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

A) purple
B) white
C) pure-breeding purple
D) pure-breeding white
E) heterozygous

Question 19

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

A) AA
B) Aa
C) aa
D) Either Aa or aa
E) Either AA or Aa

Question 20

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

A) 1/2
B) 1/4
C) 1/16
D) 1/64
E) 1/128

Question 21

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?

A) CC
B) Cc
C) cc
D) CC or Cc

Question 22

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 23

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?

A) 1/4
B) 1/2
C) 3/4
D) 2/3
E) 1/3

Question 24

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 25

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

A) 1:1
B) 3:1
C) 1:1:1:1
D) 2:1
E) 1:2:1

Question 26

How did Sutton's chromosome theory of inheritance link Mendel's work with a more mechanistic understanding of heredity?

Question 27

What important genetics concept is being shown in the diagram?

A) Mendel's principle of independent assortment
B) Mendel's principle of segregation
C) The molecular nature of alleles
D) The chi-square goodness-of-fit test
E) The results of a dihybrid cross

Question 28

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?

A) 27/256
B) 3/4
C) 9/16
D) 13/32
E) 27/64

Question 29

What is the difference between a backcross and a testcross?

Question 30

In deer mice, red eyes (r) are recessive to normal black eyes (R). Two mice with black eyes are crossed. They produce two offspring, one with red eyes and one with black eyes. Give the genotypes of parents and offspring of this cross.

Question 31

In peas, tall (T) is dominant to short (t). A homozygous tall plant is crossed with a short plant. The F₁ plants are self-fertilized to produce the F₂. Both tall and short plants appear in the F₂. If the tall F₂ plants are self-fertilized, what types of offspring and proportions will be produced?

Question 32

Albinism is a recessive condition resulting from the inability to produce the dark pigment melanin in skin and hair. A man and woman with normal skin pigmentation want to have two children. The man has one parent with albinism; the woman has parents with normal pigmentation but a brother with albinism.
a. What is the probability that at least one child will be have albinism?
b. What is the probability of both children having normal pigmentation?

Question 33

Using the diploid cell shown here (at interphase), illustrate/describe Mendel's principles of segregation and independent assortment.

Question 34

What conclusions did Mendel make from his monohybrid crosses?

Question 35

Sex in mammals is determined by the X and Y sex chromosomes: Males are XY and females are XX. How do you explain the 50-50 sex ratio in mammalian progeny?

Question 36

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 37

In peas, tall (T) is dominant to short (t). A homozygous tall plant is crossed with a short plant. The F₁ plants are self-fertilized to produce the F₂. Both tall and short plants appear in the F₂. If the short F₂ plants are self-fertilized, what types of offspring and proportions will be produced?

Question 38

You have learned that purple flowers are dominant to white in Mendel's peas. When walking the grounds of Mendel's monastery, you come across a stray purple pea plant. You suspect that it is descended from Mendel's experimental plants, but you have no idea of its exact heritage. Propose two ways that you could determine the plant's genotype with respect to the flower color. Assume that you have any other pea plants that you might want to use in your analysis. Provide expected results and interpretations of possible results for your experiments. Which of the two ways would be easier and why?

Question 39

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

A) 3/64
B) 1/64
C) 1/8
D) 1/32
E) 1/16

Question 40

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 41

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.)

A) 3/256
B) 3/32
C) 3/16
D) 3/8
E) 3/4

Question 42

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?

A) one
B) two
C) three
D) four
E) A correct answer can't be determined.

Question 43

A man has either an AaBB or AABb genotype with equal probability. Assume these genes assort independently. What is the overall probability that the man will produce an Ab gamete?

Question 44

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?

A) 3/4
B) 1/16
C) 9/16
D) 3/16
E) 1/2

Question 45

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

A) 3/256
B) 3/32
C) 3/16
D) 3/8
E) 3/4

Question 46

A man has either an AaBB or AABb genotype with equal probability. Assume these genes assort independently. What is the probability of the man producing an AB gamete?

Question 47

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?

A) 3/4
B) 1/16
C) 9/16
D) 3/16
E) 1/2

Question 48

For a particular plant, red flowers (A) are dominant over yellow flowers (a). An initial cross was made between a plant that was correct-breeding for red flowers and another plant true-breeding for yellow flowers. F₁ progeny, all having red flowers, were allowed to self- pollinate and form seeds, which were then planted to generate F₂ progeny. Pollen from all the resulting F₂ plants was pooled and used to fertilize true-breeding yellow plants. What proportion of the progeny resulting from this cross would be expected to have yellow flowers?

Question 49

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?

A) BBSS
B) BbSS
C) BBSs
D) BbSs
E) bbss

Question 50

The following cross produced 125 progeny: aaBbCcDd × AaBbccDD. Assume all the genes assort independently and that the uppercase letters represent dominant alleles.
a. How many offspring are expected to express the phenotype ABCD?
b. How many offspring are expected to have the genotype aaBBccDd?
c. How many offspring are expected to have the genotype AaBbCcDd?

Question 51

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?

A) RRYY
B) RrYY
C) RRYy
D) RrYy
E) rryy

Question 52

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 53

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?

A) 1/4
B) 1/2
C) 1/16
D) 9/16
E) 1 (100%)

Question 54

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?

A) 3/4
B) 1/16
C) 9/16
D) 3/16
E) 1/2

Question 55

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?

A) RRYY
B) RrYY
C) RRYy
D) RrYy
E) rryy

Question 56

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

A) After the end of meiosis I, two genetically distinct types of cells were present.
B) The gametes shown could NOT have resulted from a single meiotic event with two divisions
C) Independent assortment takes place during meiosis II.

Question 57

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?

A) BBSS
B) BbSS
C) BBSs
D) BbSs
E) bbss

Question 58

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.)

A) 3/256
B) 3/32
C) 3/16
D) 3/8
E) 3/4

Question 59

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?

A) BBSs
B) BBss
C) BbSS
D) BbSs
E) Bbss

Question 60

Compare and contrast Mendel's principle of segregation and the principle of independent assortment.

Question 61

In a plant species, you notice that purple and yellow leaf colors, as well as hairy and smooth stems, segregate. In this species, yellow (P) is dominant to purple (p), and hairy (S) is dominant to smooth (s). You cross a plant with purple leaves and hairy stems to a plant with yellow leaves and hairy stems and generate the following progeny: a. Indicate the most likely genotypes for each parent.
b. Propose a hypothesis to explain the progeny results. Based on this hypothesis, what ratios are expected for each of the four classes of progeny?
c. Using the chi-square method, test your hypothesis and indicate whether you accept or reject it.

Question 62

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?

A) 0.2
B) 0.4
C) 0.8
D) 1.2
E) 1.6

Question 63

Let us assume that hairy toes (hh) and brittle ear wax (ww) are both recessive traits in humans. In families of three children where both parents are heterozygotes at both loci (they have smooth toes and sticky ear wax) what is the probability that the family will consist of one hairy-toed, brittle ear-waxed boy and two smooth-toed, sticky ear-waxed girls?

Question 64

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

Question 65

Two pea plants with purple flowers are crossed. Among the offspring, 63 have purple flowers, and 17 have white flowers. With a chi-square test, compare the observed numbers with a 3:1 ratio and determine if the difference between observed and expected could be a result of chance.