genetics exam 4 practice questions

1. 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 phenotype from a cross aabb × AABB?

a. 1 (100%)

1. In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if rabbits with the cross cchch ´ chc.

a. 1 chinchilla:1 Himalayan

1. In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if rabbits with the cross Cch ´ cc.

a. 1 full color:1 Himalayan

1. In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if rabbits with the cross Cch ´ chc.

a. 1 full color:1 Himalayan

1. 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 phenotype from a cross AaBb × AaBb?

a. 9/16

1. A mother with blood type A has a child with blood type A. Give all possible blood types for the father of this child.

a. A, B, AB, O

1. A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.

a. A, B, AB, O

1. A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.

a. A, B, O

1. In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and A?

a. A, B, and AB only

1. A mother of blood type A gives birth to a child with blood type O. Which of the following could NOT be the blood type of the father?

a. AB

1. Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What is the genotype of the pink progeny?

a. A_ B_ and A_ bb

1. If an organism of genotype Aa is used for a test cross, what is the genotype of the other individual used in the cross?

a. Aa

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

a. Aa ´ Aa

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

a. Aa ´ aa

1. Suppose that the "fabulous" phenotype is controlled by two genes, A and B, as shown in the diagram below. Allele A produces enough enzyme 1 to convert "plain" to "smashing." Allele a produces no enzyme 1. Allele B produces enough enzyme 2 to convert "smashing" to "fabulous." Allele b produces no enzyme 2. The A and B genes are both autosomal and assort independently. What will be the phenotype(s) of the F1 offspring of a true-breeding "fabulous" father and a true-breeding "plain" mother (aa bb)?

a. All "fabulous"

1. You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a pure-breeding brown spider with a pure-breeding green spider. Predict the phenotype of the progeny.

a. All brown

1. A mother with blood type A has a child with blood type AB. Give all possible blood types for the father of this child.

a. B, AB

1. Pea plants have seven different types of chromosomes. A chromosome with a centromere at the very end is called

telocentric.

1. If a healthy cell passes the G1/S checkpoint,

DNA will be replicated.

1. Suppose that a diploid cell contains 8 chromosomes (2n = 8). How many different combinations in the gametes are possible?

16

1. A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of telomeres in a rat cell in G2?

168

1. Pea plants have seven different types of chromosomes. A nucleus in the pea endosperm contains how many chromosomes?

21

1. A pollen grain that lands on a stigma grows a pollen tube to deliver ___ (how many?) sperm to the ovary. Fusion of a sperm with an egg produces a ___ n cell called a___.

2; 2; zygote

1. To provide food for the developing embryo, a tissue called endosperm is produced through double fertilization. Endosperm has a ploidy of

3n.

1. A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of chromosomes present in the cell during metaphase I of meiosis?

42

1. 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%

1. Which of the following statements is true? The genotype is the physical appearance of a trait. Alleles, genes, and loci are different names for the same thing. The phenotype of a dominant allele is never seen in the F1 progeny of a monohybrid cross. A testcross can be used to determine whether an individual is homozygous or heterozygous. All of these statements are true.

A testcross can be used to determine whether an individual is homozygous or heterozygous.

1. Which of the following statements is true? The probability of a woman giving birth to three girls in a row is 1/8. The chi-square test is used to determine if observed outcomes are consistent with expected outcomes. The probability of two or more independent events occurring together is calculated by multiplying their independent probabilities. Branched diagrams are used for determining probabilities of various phenotypes or genotypes for genetic crosses involving more than one gene pair. All of these statements are true.

All of these statements are true.

1. A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in 5. The figure shows a chromosomal separation taking place. The letters stand for genes; capital and lowercase stand for different alleles. The diploid chromosome number in this organism is four. What process is shown?

Anaphase of meiosis II

1. Which statement is true? Eubacteria are more closely related to archaea than they are to eukaryotes. Archaea are more closely related to eukaryotes than they are to eubacteria. Eukaryotes are more closely related to eubacteria than they are to archaea. Viruses are more closely related to prokaryotes than they are to eukaryotes. Eubacteria, archaea, and eukaryotes are all equally related.

Archaea are more closely related to eukaryotes than they are to eubacteria.

1. Prokaryotic chromosomes do not have telomeres because they

are circular.

1. What process is unique to plants?

Double fertilization

1. Which of the following statements is false?

Generally, chromosomes of eukaryotes are circular.

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

Genes are carried on chromosomes.

1. 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?

Homozygous round stigma pollinated with homozygous wrinkled

1. A dividing eukaryotic cell is treated with a drug that inhibits the molecular motors associated with kinetochores. At which cell cycle stage would it stop?

M (metaphase)

1. Which of the following occurs during prometaphase?

Microtubules attach to the kinetochores.

1. 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

1. 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.

1. Which of the following does NOT occur during the G2 phase of the cell cycle?

The cell divides.

1. 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 4 black puppies and 1 brown. What can you conclude about the genotype of the black parent?

The genotype must be Bb.

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 queen is heterozygous for a particular gene, what is the probability that a female will inherit the recessive allele from her mother? What is the probability that a male 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%.

1. What might be the result if breakdown of the shugoshin protein were premature?

The separation of sister chromatids would occur prematurely.

1. In a cross between pure-breeding tall plants with pure-breeding short plants, all of the F1 are tall. When these plants are allowed to fertilize themselves, the F2 plants occur in a ratio of 3 tall: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

1. Which of these are NOT prokaryotes?

Viruses

1. In order to be functional, a eukaryotic chromosome requires all of the following except

a plasmid.

1. A chi-square test was performed and indicated that the observed numbers of offspring were significantly different from the expected. Which of the following P-values would support this conclusion?

a. 0.024

1. Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 60% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes?

a. 0.15

1. You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However the L allele is only 60% penetrant. You cross two heterozygous giraffes. What proportion of offspring would you expect to exhibit the long ossicone phenotype? Assume the penetrance of L applies equally to both homozygotes and heterozygotes.

a. 0.45

1. You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However, the L allele is only 60% penetrant. You cross two heterozygous giraffes. What proportion of offspring would you expect to exhibit the short ossicone phenotype? Assume the penetrance of L applies equally to both homozygotes and heterozygotes.

a. 0.55

1. 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 significantly different from expected Mendelian ratios, so you perform a chi-square test. What is the chi-square value for this cross?

a. 0.8

1. 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. 1/16

1. Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is 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. 1/16

1. 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 AaBb × AaBb?

a. 1/16

1. 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 AaBb × AABB?

a. 1/16

1. 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

1. 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. 1/2

1. 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. 1/2

1. 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

1. Crossing two yellow mice results in 2/3 yellow offspring and 1/3 nonyellow offspring. What percentage of offspring would you expect to be nonyellow if you crossed two nonyellow mice?

a. 100%

1. In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if rabbits with the cross Cc ´ chc.

a. 2 full color:1 Himalayan:1 albino

1. A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of chromosomes in a polar body cell from a rat?

a. 21

1. In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if rabbits with the cross Ccch ´ Cch.

a. 3 full color:1 chinchilla

1. 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

1. 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. 3/32

1. Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is 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

1. 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. 3/8

1. Pea plants have seven different types of chromosomes. The nucleus of a megaspore in a pea ovary would contain how many chromosomes?

a. 7

1. Suppose that the "fabulous" phenotype is controlled by two genes, A and B, as shown in the diagram below. Allele A produces enough enzyme 1 to convert "plain" to "smashing." Allele a produces no enzyme 1. Allele B produces enough enzyme 2 to convert "smashing" to "fabulous." Allele b produces no enzyme 2. The A and B genes are both autosomal and assort independently. What will be the expected ratio of the F2 offspring of the F1 generation?

a. 9 "fabulous":3 "smashing":4 "plain"

1. Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is 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. 9/16

1. You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a pure-breeding brown spider with a pure-breeding green spider. Predict the genotype of the progeny.

a. B/bg

1. Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow. A black female Labrador retriever was mated with a yellow male. Half of the puppies were black and half were yellow. If the genotype of the black female parent was Bb Ee, then what was the genotype of the other parent?

a. BB ee

1. 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. What is the genotype of the female?

a. BBSs

1. 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

1. While doing field work 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: Which cross is likely to have at least one parent with the genotype RR?

a. Crosses 2 and 3

1. Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What kind of gene interaction is this?

a. Dominant epistasis

Which of the following statements is false?

a. Errors in chromosome separation are rarely a problem for an organism.

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

a. Heterozygous

1. The R locus determines flower color in a new plant species. Plants that are genotype RR have red flowers, and plants that are rr have white flowers. However, Rr plants have pink flowers. What type of inheritance does this demonstrate for flower color in these plants?

a. Incomplete dominance

1. In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black:2 gray:1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?

a. One gene pair with incomplete dominance

1. Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow. What type of gene interaction does this represent?

a. Recessive epistasis

1. Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is 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, 51 wrinkled and green. What is the likely genotype of the parent in question?

a. RrYy

1. Round seeds (R) is dominant to wrinkled seeds (r), and yellow seeds (Y) is 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

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

a. Simple traits that are easy to identify

1. Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia:1 normal. What is the most likely explanation for these observations?

a. The allele that causes achondroplasia is a recessive lethal allele.

1. Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What is the genotype of the black progeny?

a. aa B_

1. Coat color is determined by two loci in large cats. Two pink panthers fall in love and produce a large litter of baby panthers with the following phenotypic ratios: 12/16 pink; 3/16 black; and 1/16 white. What is the genotype of the white progeny?

a. aa bb

1. 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. What is the genotype of the brown, spotted male?

a. bbss

1. 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

1. Interactions among the human ABO blood group alleles involve _______ and ________.

a. co-dominance; complete dominance

1. The process of splitting the cytoplasm, which separates one cell into two, is termed

a. cytokinesis.

1. Genes come in different versions called

alleles

1. In eukaryotes, chromosomes do not contain

ribosomes.

1. The attachment point on the chromosome for spindle microtubules is the

centromere.

Chromosome movement during anaphase is a result of

disassembly of tubulin molecules by molecular motor proteins.

1. In a flowering plant, the male part of the flower (the stamen) produces haploid microspores that divide by _____to produce sperm.

mitosis

1. The highly organized internal scaffolding of the nucleus is called the

nuclear matrix.

1. In prokaryotes, replication usually begins at a specific place on the chromosome called the

origin of replication.

1. Diploid cells are cells with

two sets of chromosomes.

1. Polydactyly is the condition of having extra fingers or toes. Some polydactylous persons possess extra fingers or toes that are fully functional, whereas others possess only a small tag of extra skin. This is an example of

variable expressivity