AP BIO Unit 5

Several members of a family are found to involuntarily sneeze when exposed to bright lights, such as sunlight. Following analysis of the condition in the family, a doctor predicts that the symptoms have an underlying genetic basis. A pedigree of the family is shown in Figure 1. <insert pedigree> For this condition, which of the following modes of inheritance is most consistent with the observations? A Autosomal dominant B Autosomal recessive C X-linked dominant D X-linked recessive

A Autosomal dominant

Directions: Each group of questions below concerns an experimental or a laboratory situation. In each case, first study the description of the situation. Then choose the one best answer to each question following it. In dogs, one pair of alleles determines coat color (dark and albino). Another pair of alleles determines hair length (short and long). Thus, each gamete will contain one of the coat-color alleles, C or c and one of the hair-length alleles, B or b. In repeated crosses of a specific dark, short-haired dog with an albino, long-haired dog, all the offspring were dark with short hair, as shown in cross I. However, in subsequent crosses of another dark, short-haired dog with a dark, long-haired dog, the ratios shown in cross II below were obtained. <insert table> In cross II, the genotype of the dark, short-haired parent is A CcBb B ccbb C CCBB D CCbb E ccBB

A CcBb

<insert image> The diagram above illustrates which of the following processes? A Crossing-over B Base pair substitution C Duplication D Deletion E Posttranscriptional processing

A Crossing-over

<insert image> Based on Figure 1, which of the following questions could best be addressed? A Does synapsis of homologous chromosomes in the parent cell contribute to an increase in genetic diversity in the daughter cells? B Do sister chromatids separate and form diploid daughter cells? C Do chromatids from nonhomologous chromosomes rearrange to produce identical daughter cells? D Does synapsis of nonhomologous chromosomes produce daughter cells that are identical to the parent cell?

A Does synapsis of homologous chromosomes in the parent cell contribute to an increase in genetic diversity in the daughter cells?

In the spring and summer, the fur of an arctic fox contains a pigment called melanin that gives the fox's fur a dark color. In the fall and winter, the fur of the arctic fox is white. Which of the following most likely explains how the changing seasons result in changing fur color in an arctic fox? A Environmental factors cause changes in gene expression, resulting in seasonal variations in pigment production. B Environmental factors cause different mutations in DNA during different seasons, resulting in seasonal changes in fur phenotype. C Environmental factors cause proteins to be translated using different genetic codes during different seasons, resulting in variations in pigment production. D Environmental factors cause enzymes to react with different substrates, resulting in the accumulation of different pigments.

A Environmental factors cause changes in gene expression, resulting in seasonal variations in pigment production.

In sweet pea plants, purple flower color is dominant over red flower color and long pollen grain shape is dominant over round pollen grain shape. Two sweet pea plants that are heterozygous for both flower color and pollen grain shape are crossed with one another. A geneticist is surprised to observe that there are far fewer round, purple offspring and long, red offspring than were predicted by the 9:3:3:1 expected phenotypic ratio. Which of the following statements provides the most reasonable prediction to account for the deviation from the expected results? A In sweet pea plants, the gene for flower color and the gene for pollen grain shape are genetically linked. B In sweet pea plants, the genes for flower color and for pollen grain shape both exhibit codominance. C Several mutations occurred spontaneously producing a deviation from the expected phenotypic ratios of the offspring. D The genes for flower color and pollen grain shape are inherited independently because of the law of independent assortment.

A In sweet pea plants, the gene for flower color and the gene for pollen grain shape are genetically linked.

<Insert image> During prophase I replicated homologous chromosomes pair up and undergo synapsis. What testable question is generated regarding synapsis and genetic variability by Figure 1 ? A Is the distance between two gene loci related to crossover rate? B Does crossing over occur more often in some chromosomes than in others? C Is crossing over inhibited by methylation? D Is crossing over promoted by methylation?

A Is the distance between two gene loci related to crossover rate?

Scientists have found that DNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation? A Is the level of genetic variation in the gametes related to the amount of DNA methylation observed? B Without crossing-over, will gametes be viable and be able to produce zygotes? C Does DNA methylation result in shorter chromosomes? D Is this species of fungus a diploid organism?

A Is the level of genetic variation in the gametes related to the amount of DNA methylation observed?

Directions: Each group of questions below concerns an experimental or a laboratory situation. In each case, first study the description of the situation. Then choose the one best answer to each question following it. In dogs, one pair of alleles determines coat color (dark and albino). Another pair of alleles determines hair length (short and long). Thus, each gamete will contain one of the coat-color alleles, C or c and one of the hair-length alleles, B or b. In repeated crosses of a specific dark, short-haired dog with an albino, long-haired dog, all the offspring were dark with short hair, as shown in cross I. However, in subsequent crosses of another dark, short-haired dog with a dark, long-haired dog, the ratios shown in cross II below were obtained. <Insert table> Which of the following correctly describes the relationship of the dark-coat-color allele to the albino condition? A It is dominant. B It is recessive. C It is codominant. D It is a polygenic inheritance pattern. E The alleles are linked.

A It is dominant.

Researchers hypothesized that red eye color in Japanese koi, a type of fish, is due to a mutation. To study the inheritance of red eye color in koi, the researchers conducted breeding experiments over several generations. The results are summarized in Figure 1. <insert pedigree> Based on the data in Figure 1, which of the following is the best prediction of the mode of inheritance of red eyes in Japanese koi? A The allele for red eyes is inherited in an autosomal dominant pattern. B The allele for red eyes is inherited in an autosomal recessive pattern. C The allele for red eyes is inherited in an X-linked recessive pattern. D The allele for red eyes is inherited in an X -linked dominant pattern.

A The allele for red eyes is inherited in an autosomal dominant pattern.

A student crosses a pure-breeding line of red-flowered poinsettias with a pure-breeding line of white-flowered poinsettias. The student observes that all the plants in the F1 generation have pink flowers. The student then crosses the F1 plants with one another and records observations about the plants in the F2 generation. The student will use the F2 data to perform a chi-square goodness-of-fit test for a model of incomplete dominance. The setup for the student's chi-square goodness-of-fit test is presented in Table 1. <Insert table> The critical value for a chi-square test with a significance level of p=0.05 and 2 degrees of freedom is 5.99. Which of the following statements best completes the student's chi-square goodness-of-fit test? A The calculated chi-square value is 1.53, and the null hypothesis cannot be rejected. B The calculated chi-square value is 1.53, and the null hypothesis can be rejected. C The calculated chi-square value is 98, and the null hypothesis cannot be rejected. D The calculated chi-square value is 98, and the null hypothesis can be rejected.

A The calculated chi-square value is 1.53, and the null hypothesis cannot be rejected.

In a strain of tomato plants, short plant height and small fruit size are traits that display autosomal recessive patterns of inheritance. To investigate whether the traits segregate independently, researchers cross a pure-breeding line of tall tomato plants that have large fruits with a pure-breeding line of short tomato plants that have small fruits. The researchers observe that all the plants in the F1 generation are tall and have large fruits. The researchers cross the F1 plants with one another to generate an F2 generation. The researchers record observations for the F2 generation and will use the data to perform a chi-square goodness-of-fit test for a model of independent assortment. The setup for the chi-square goodness-of-fit test is shown in Table 1. <insert table> The researchers choose a significance level of p=0.05. Which of the following best completes the chi-square goodness-of-fit test? A The calculated chi-square value is 9.24, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected. B The calculated chi-square value is 9.24, and the critical value is 9.49. The null hypothesis of independent assortment cannot be rejected. C The calculated chi-square value is 13.13, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected. D The calculated chi-square value is 13.13, and the critical value is 9.49. The null hypothesis of independent assortment cannot be rejected.

A The calculated chi-square value is 9.24, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected.

In a strain of tomato plants, short plant height and small fruit size are traits that display autosomal recessive patterns of inheritance. To investigate whether the traits segregate independently, researchers cross a pure-breeding line of tall tomato plants that have large fruits with a pure-breeding line of short tomato plants that have small fruits. The researchers observe that all the plants in the F1 generation are tall and have large fruits. The researchers cross the F1 plants with one another to generate an F2 generation. The researchers record observations for the F2 generation and will use the data to perform a chi-square goodness-of-fit test for a model of independent assortment. The setup for the chi-square goodness-of-fit test is shown in Table 1. <insert table> The researchers choose a significance level of p=0.05. Which of the following best completes the chi-square goodness-of-fit test? A The calculated chi-square value is 9.24, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected. B The calculated chi-square value is 9.24, and the critical value is 9.49. The null hypothesis of independent assortment cannot be rejected. C The calculated chi-square value is 13.13, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected. D The calculated chi-square value is 13.13, and the critical value is 9.49. The null hypothesis of independent assortment cannot be rejected.

A The calculated chi-square value is 9.24, and the critical value is 7.82. The null hypothesis of independent assortment can be rejected.

Insulin is a hormone produced by some pancreatic cells. Scientists have isolated the DNA sequence that codes for human insulin production. Which of the following best predicts the effect of inserting this gene into the DNA of a bacterial cell? A The recombinant bacterium will produce human insulin using its own transcription and translation machinery. B The recombinant bacterium will not transcribe the human insulin gene because this gene is not normally found in the bacterial genome. C The recombinant bacterium will transcribe the gene but will be unable to translate the mRNA. D The recombinant bacterium will die because it has been exposed to foreign DNA .

A The recombinant bacterium will produce human insulin using its own transcription and translation machinery.

In pea plants, purple flower color is dominant to red flower color and long pollen grains are dominant to round pollen grains. Researchers crossed two pure-breeding lines of the pea plants to investigate whether the genes controlling flower color and pollen shape segregate independently. The procedure for the genetics experiment is summarized in Figure 1. <insert image> Which of the following tables best shows the expected values in the F2 generation for a chi-square goodness-of-fit test for a model of independent assortment?

B

The diploid number of chromosomes in the cell of a domesticated dog is 78. Which of the following options includes the correct number of chromosomes in a cell after each cellular process (G2 checkpoint, meiosis, and fertilization, respectively)?

B

<insert table> The students plan to use a significance level of p=0.01. Which of the following is the most appropriate critical value for the students to use in their chi-square goodness-of-fit test? A 7.82 B 11.34 C 13.28 D 326.7

B 11.34

<insert table> The mean map distance between gene R and gene L is closest to which of the following? A 0.28 map units B 28 map units C 0.14 map units D 14 map units

B 28 map units

Two fruit fly mutations are ebony body (e) and sepia eyes (s). Four different students performed dihybrid crosses with flies that were heterozygous with a mutant allele and a wild-type allele for both genes (EeSs×EeSs). The results are shown in Table 1. <insert table> The mean number of fruit flies per student that are homozygous recessive for both genes is closest to which of the following? A 89.75 B 29.0 C 22.75 D 18.5

B 29.0

R. C. Punnett conducted experiments on the inheritance of traits in the sweet pea, Lathyrus odoratus. In one experiment, he crossed two different true-breeding sweet pea plant strains, one with erect petals and long pollen, and the other with hooded petals and round pollen. All the offspring (F1 generation) had erect petals and long pollen (Figure 1). <Insert table> How many degrees of freedom should be used when looking up the critical value for a chi-square analysis of the ratios of phenotypes observed among the F2 offspring versus the expected phenotypic ratio assuming independent assortment? A 2 B 3 C 4 D 5

B 3

Sex chromosomes determine the phenotype of sex in humans. Embryos containing XX chromosomes develop into females, and embryos containing XY chromosomes develop into males. The sex chromosomes separate during meiosis, going to different gamete cells. A woman is heterozygous for the X-linked recessive trait of hemophilia A. Her sex chromosomes can be designated as XHXh. During meiosis the chromosomes separate as shown in Figure 1. <insert image> If the woman and a man with normal clotting function have children, what is the probability of their children exhibiting hemophilia A? A 50 percent for daughters, 0 percent for sons B 50 percent for sons, 0 percent for daughters C 50 percent for all children D 0 percent for all children

B 50 percent for sons, 0 percent for daughters

Researchers performed a dihybrid cross with coffee bean plants to investigate whether the inheritance of two traits (height and stem circumference) follows Mendel's law of independent assortment. The data for the F2 generation are presented in Table 1. Which of the following is closest to the calculated chi-square (χ2) value for the data presented in Table 1? A 8.35 B 72.01 C 98.00 D 2,546.00

B 72.01

The Russian blue is a rare breed of cat that is susceptible to developing cataracts on the eyes. Scientists hypothesize that this condition is inherited as a result of a mutation. Figure 1 shows a pedigree obtained in a study of cats owned by members of the Russian Blue Club in Sweden. <insert pedigree> Based on the inheritance pattern shown in Figure 1, which of the following best predicts the nature of the original mutation? A A recessive mutation on the X chromosome B A recessive mutation on a somatic chromosome C A dominant mutation on the X chromosome D A dominant mutation on a somatic chromosome

B A recessive mutation on a somatic chromosome

Glycolysis is a metabolic pathway that converts glucose into pyruvate and is observed in each of the three domains. The hexokinase family of enzymes is required during glycolysis to phosphorylate six-carbon sugars. Researchers designed a general hexokinase inhibitor that is effective in the neurons of rats. Which of the following best predicts the effect of adding this inhibitor to a culture of plant cells? A Plant cells will be unaffected by the inhibitor as they do not perform glycolysis. B Plant cells will be unable to perform glycolysis due to the inhibitor and will die. C Plant cells will be unable to perform photosynthesis due to the inhibitor and will die. D Plant cells will still be able to perform glycolysis since plant hexokinase is not structurally similar to animal hexokinase.

B Plant cells will be unable to perform glycolysis due to the inhibitor and will die.

Humans have a diploid number (2n) of 46. Which of the following statements best predicts the consequence if meiosis did not occur during gametogenesis? A The gametes would get larger from one generation to the next. B The chromosome number would double with each generation. C The chromosome number would be halved with each generation. D The chromosome number would triple with each generation.

B The chromosome number would double with each generation.

In pea plants, flower color and the length of the flower's pollen grains are genetically determined. Researchers studying pea plants crossed homozygous dominant pea plants with homozygous recessive pea plants. The F1 plants were then crossed, and the number of offspring with each phenotype was recorded. The researchers' observed data, however, differed from the expected data. The researchers did a chi-square analysis and calculated the chi-square value to be 5.5. Based on their calculation, the researchers would most likely conclude which of the following? A The genes that determine these two traits are likely on the same chromosome. B The differences between observed data and expected data are due to chance. C The genes mutated since the researchers began the experiment and now have a different inheritance pattern. D The allele frequencies of the offspring have changed, suggesting the population is evolving.

B The differences between observed data and expected data are due to chance.

A true-breeding variety of wheat that produces deep-red-colored grain was crossed with a true-breeding variety that produces a white-colored grain. The resulting F1 offspring all had medium-red-colored grain. Five crosses of the F1 plants were all grown under the same conditions and resulted in plants with a variety of grain color, as indicated in Table 1. <insert table> Which of the follow indicates the mean number per cross of F2 plants producing medium-red grain and correctly explains the distribution of the phenotypes? A The mean number of medium-red phenotypes per cross is 20.8. The distribution of phenotypes suggests that grain color is under environmental control. B The mean number of medium-red phenotypes per cross is 20.8. The distribution of phenotypes suggests that multiple genes are involved in grain color determination. C The mean number of medium-red phenotypes per cross is 104. The distribution of phenotypes suggests that grain color is under environmental control. D The mean number of medium-red phenotypes per cross is 104. The distribution of phenotypes suggests that multiple genes are involved in grain color determination.

B The mean number of medium-red phenotypes per cross is 20.8. The distribution of phenotypes suggests that multiple genes are involved in grain color determination.

A genetic counselor is consulted by a young man who is worried about developing Huntington's disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with Huntington's disease, and the news has caused him to consider his own risk of developing the disorder. Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing Huntington's disease and transmitting it to his children? A Were you and your cousin born in the same geographical area? B Were your parents or grandparents ever diagnosed with Huntington's disease? C Were you in physical contact with a person diagnosed with Huntington's disease? D Were you ever exposed to substances that are suspected of being mutagens?

B Were your parents or grandparents ever diagnosed with Huntington's disease?

Tay-Sachs disease is a rare inherited disorder caused by an autosomal recessive allele of the HEXA gene. Affected individuals exhibit severe neurological symptoms and do not survive to reproductive age. Individuals who inherit one copy of the allele (Tay-Sachs carriers) typically show no symptoms of the disorder. The frequencies of Tay-Sachs carriers in the general population of North America and in three different subpopulations are presented in the table. <insert table>

B Answer with pedigree

Within a forest ecosystem, there is a large amount of diversity among members of a warbler species. Of the following stages of meiosis illustrated for a typical cell, which contributes most to diversity among the warblers?

C

If 2n = 48 for a particular cell, then the chromosome number in each cell after meiosis would be A 96 B 48 C 24 D 12 E 6

C 24

Researchers investigated whether time of day affects the rate at which certain mRNAs produced by plants are broken down. At either 1 hour after the start of the light period (morning) or 8 hours after the start of the light period (afternoon), the researchers treated identical plant seedlings with a compound that blocks transcription (time=0min). The researchers measured the percent remaining of two mRNAs, mRNA G and mRNA H, over the course of 120 minutes. The data are shown in Figure 1. <insert image> Based on the data, which of the following best describes the relationship between light and the degradation of mRNA G and mRNA H? A Exposure to light causes the degradation of both mRNA G and mRNA H. B mRNA G and mRNA H degrade at the same rate during morning exposure to light. C A longer exposure to light increases the rate of mRNA G degradation but not of mRNA H degradation. D Exposure to more-intense afternoon light causes both mRNA G and mRNA H to degrade more rapidly in the afternoon than in the morning.

C A longer exposure to light increases the rate of mRNA G degradation but not of mRNA H degradation.

Huntington's disease has been traced to the number of CAG repeats in the HTT gene, which is located on chromosome 4. The phenotypic influence of individual alleles with different numbers of repeats is shown in Table 1. <insert table> Which of the following is most likely the immediate cause of the first appearance of Huntington's disease in a person? A A point mutation occurs in the HTT gene. B The first appearance of the CAG repeat occurs in the HTT gene. C An allele with more than 39 CAG repeats was inherited by the affected person. D The person inherited two alleles that each contained 20 CAG repeats.

C An allele with more than 39 CAG repeats was inherited by the affected person.

An African violet grower observes that genetically identical African violet plants growing near the walls of the greenhouse have white flowers, that plants growing farther away from the walls have pale blue flowers, and that plants growing nearest the center of the greenhouse have dark blue flowers. Which of the following best explains the differences in flower color of the African violets in the greenhouse? A Warmer temperatures result in genotypic alterations, which result in flower color differences. B The plants along the walls of the greenhouse are homozygous recessive and therefore have white flowers. C An enzyme responsible for flower color does not fold correctly in cooler temperatures, and the greenhouse is warmest in the center. D More light is available along the walls of the greenhouse, so the flowers need less pigment to absorb sunlight for photosynthesis.

C An enzyme responsible for flower color does not fold correctly in cooler temperatures, and the greenhouse is warmest in the center.

Trisomy 21 is a condition in which a child is born with an extra chromosome in pair 21. Researchers assessed the frequency of children born with trisomy 21 by age of the mothers at birth (maternal age) and primary cause of the error leading to trisomy 21. The findings are presented in Figure 1. <insert table> Based on the data in Figure 1, which of the following is most likely the primary cause of the pattern of frequency of trisomy 21 births in the selected maternal age-groups? A At older maternal ages, there is an increase in the number of errors during mitosis, which leads to an increase in nondisjunction during egg production. B The incidence of nondisjunction errors in meiosis during sperm production is positively correlated with increasing maternal age. C At older maternal ages, the incidence of errors in meiosis during egg production increases, which leads to an increase in nondisjunction. D Errors in meiosis leading to nondisjunction are more likely to occur during meiosis I than during meiosis II .

C At older maternal ages, the incidence of errors in meiosis during egg production increases, which leads to an increase in nondisjunction.

Table 1 shows the stage and number of cells and chromosomes per cell at the end of the stage in a 2n=24 organism. <insert table> Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis I? A Each daughter cell contains 12 chromatids. Each chromatid is one of two from a single chromosome with the other one of the pair found in the other daughter cell. B Each daughter cell contains 12 chromosomes, each composed of two chromatids. Since the chromosomes were randomly divided, one daughter cell may contain both of a pair of homologous chromosomes, while the other cell contains both of another pair of homologous chromosomes. C Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell. D Each daughter cell contains 24 separate chromatids. Since every two chromatids were originally joined, forming one homologous chromosome, the number of chromatids is divided by two to determine the number of chromosomes.

C Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.

<Insert image> Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ? A Does crossing-over generate more genetic diversity than the fusion of gametes does? B Does DNA methylation prevent independent assortment during metaphase II? C How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity? D Do daughter cells that are not genetically identical to parent cells produce viable zygotes?

C How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?

The tadpoles of Mexican spadefoot toads are known to exhibit phenotypic plasticity depending on food availability. Tadpole mouthparts can vary significantly, prompting researchers to categorize them as either omnivore-morph or carnivore-morph. Carnivore-morph tadpoles are larger and have mouthparts that are better suited for predation. Remarkably, carnivore-morph tadpoles can change into omnivore-morph tadpoles when the food supply changes. Which of the following best describes an advantage of the phenotypic plasticity displayed by the tadpoles? A It allows the tadpoles to change their genome in response to environmental pressures. B It enables the tadpoles to develop into a distinct species of toads. C It gives the tadpoles increased versatility with respect to diet. D It allows the tadpoles to delay metamorphosis until there is maximal food available for the adults.

C It gives the tadpoles increased versatility with respect to diet.

In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a color-blind son, which of the following must be true? A The father is color-blind. B Both parents carry the allele for color blindness. C Neither parent carries the allele for color blindness. D The father carries the allele for color blindness. E The mother carries the allele for color blindness.

E The mother carries the allele for color blindness.

R. C. Punnett conducted experiments on the inheritance of traits in the sweet pea, Lathyrus odoratus. In one experiment, he crossed two different true-breeding sweet pea plant strains, one with erect petals and long pollen, and the other with hooded petals and round pollen. All the offspring (F1 generation) had erect petals and long pollen (Figure 1). <Insert tables> Sweet pea plants have a diploid (2n) chromosome number of 14. Which of the following best explains how the sweet pea plants in the parental generation produce F1 offspring with 14 chromosomes? A Meiosis I and II lead to the formation of cells with 14 chromosomes. When two cells combine during fertilization, extra chromosomes are randomly broken down, leading to offspring with 14 chromosomes. B Meiosis I and II lead to the formation of cells with 14 chromosomes. When two cells combine during fertilization, extra chromosomes with recessive traits are broken down, leading to offspring with 14 chromosomes. C Meiosis I and II lead to the formation of cells with 7 chromosomes. During meiosis I, homologous chromosomes separate. During meiosis II, sister chromatids separate. Two cells combine during fertilization to produce offspring with 14 chromosomes. D Meiosis I and II lead to the formation of cells with 7 chromosomes. During meiosis I , sister chromatids separate. During meiosis II , homologous chromosomes separate. Two cells combine during fertilization to produce offspring with 14 chromosomes.

C Meiosis I and II lead to the formation of cells with 7 chromosomes. During meiosis I, homologous chromosomes separate. During meiosis II, sister chromatids separate. Two cells combine during fertilization to produce offspring with 14 chromosomes.

For sexually reproducing diploid parent cells, which of the following statements best explains the production of haploid cells that occurs in meiosis but not in mitosis? A Separation of chromatids occurs once, and there is one round of cell division in meiosis. B Separation of chromatids occurs twice, and there are two rounds of cell division in mitosis. C Separation of chromatids occurs once, and there are two rounds of cell division in meiosis. D Separation of chromatids occurs twice, and there is one round of cell division in mitosis.

C Separation of chromatids occurs once, and there are two rounds of cell division in meiosis.

A student carries out a genetics experiment with fruit flies to investigate the inheritance pattern of the white eye trait. The student crosses a homozygous white-eyed female with a wild-type male and records observations about the flies in the F1 generation. The student plans to use the F1 data to perform a chi-square goodness-of-fit test for a model based on an X-linked recessive pattern of inheritance. The student will use one degree of freedom and a significance level of p=0.05. The setup for the student's chi-square goodness-of-fit test is presented in Table 1. <insert table> The student calculates a chi-square value of 0.36. Which of the following statements best completes the student's chi-square goodness-of-fit test? A The critical value is 0.05, and the student cannot reject the null hypothesis. B The critical value is 0.05, and the student can reject the null hypothesis. C The critical value is 3.84, and the student cannot reject the null hypothesis. D The critical value is 3.84, and the student can reject the null hypothesis.

C The critical value is 3.84, and the student cannot reject the null hypothesis.

<insert image> The diagram above depicts a karyotype of an individual human. Which of the following statements concerning the karyotype in the diagram is true? A The diagram illustrates a genetic condition found in females. B The diagram indicates a mechanism for increasing genetic diversity in subsequent generations. C The diagram illustrates the results of nondisjunction during gamete formation. D The diagram indicates Down syndrome, a genetic condition.

C The diagram illustrates the results of nondisjunction during gamete formation.

Red-green color blindness in humans is caused by a recessive allele located on the X chromosome. Figure 1 shows the potential offspring of a female who is red-green color-blind and a male with full-color vision. All of the possible male offspring would be color-blind, and all of the possible female offspring would have full-color vision. If during the production of male gametes an error in meiosis occurred, sperm containing both an X and a Y chromosome could be produced. <insert table> How would the extra chromosome affect the male offspring produced by the gamete? A None of the potential offspring would be male, because the potentially male zygote would have two X chromosomes, and the Y chromosome would be ignored. B The male offspring would all be red-green color-blind, because of interference from alleles on the Y chromosome. C The male offspring would have full-color vision, because of the presence of the extra X chromosome. D There would be no change to the phenotypes of the possible offspring, because the extra X chromosome would not be active.

C The male offspring would have full-color vision, because of the presence of the extra X chromosome.

Which of the following best explains why triploid bananas do not produce seeds? A The cells of the banana plant are unable to replicate DNA, thus preventing cell division and limiting growth. B The banana plants lack enough genetic diversity to properly hybridize. C The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis. D The production of seeds is not required because triploid plants produce gametes without fertilization.

C The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis.

<insert image> Some green sea turtle females deposit their eggs in nests that are dug on warm, tropical beaches. Researchers have studied the effects of temperature on the hatching rate and the proportion of female to male hatchlings produced at different average nest temperatures in Suriname (Figure 1). At temperatures below 23°C or above 33°C, the eggs do not develop. Which of the following best describes the results shown in Figure 1 ? A The percentage of hatchlings that survive to adulthood is directly proportional to average nest temperature. B Female sea turtles search for cooler beaches in order to have more male offspring. C Warmer nests produce more female sea turtles than do cooler nests. D The sex ratio of sea turtles is genetically determined.

C Warmer nests produce more female sea turtles than do cooler nests.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it. Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism. If three children are born to Matthew and Jane, what are the chances that the first two children will not express the trait but that the third child will be an achondroplastic dwarf? A 5/8 B 4/8 C 3/8 D 1/8 E 1/16

D 1/8

Pigeons demonstrate ZW sex determination, such that a ZZ genotype produces a male and a ZW genotype produces a female. The gene for feather color is located on the Z chromosome, and the red allele is dominant over the brown allele. Three crosses between brown male pigeons and red female pigeons were performed, and the results are shown below. Table 1. Offspring from three separate crosses of a brown male pigeon and a red female pigeon <insert table> Which of the following is the mean number of male offspring produced by the three crosses? A 27 B 20 C 11 D 9

D 9

in the pedigree above, circles represent females, squares represent males, and shaded figures represent individuals expressing a specific trait. The expression of this trait is most likely due to which of the following? A Sex-linked dominant inheritance B Sex-linked recessive inheritance C Autosomal dominant inheritance D Autosomal recessive inheritance E A codominant relationship of a single pair of alleles

D Autosomal recessive inheritance

<Insert image> The process depicted in the image above is best summarized by which of the following descriptions? A During the synthesis phase of the cell cycle, DNA molecules replicate to generate identical daughter cells. B Centromeres align specific gene sequences of homologous chromosomes during mitotic divisions. C The spindle apparatus attaches at chiasma during metaphase of mitosis. D During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.

D During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.

<insert table> Which of the following best predicts the effect of the chromosomal segregation error shown in Figure 1? A All of the resulting gametes will have an extra chromosome. B All of the resulting gametes will be missing a chromosome. C Half of the resulting gametes will have an extra chromosome and the other half will be missing a chromosome. D Half of the resulting gametes will have the correct number of chromosomes, and the other half will have an incorrect number of chromosomes.

D Half of the resulting gametes will have the correct number of chromosomes, and the other half will have an incorrect number of chromosomes.

Which of the following best explains a distinction between metaphase I and metaphase II? A The nuclear membrane breaks down during metaphase I but not during metaphase II. B Chromosomes align at the equator of the cell during metaphase II but not during metaphase I. C The meiotic spindle is needed during metaphase I but not during metaphase II. D Homologous pairs of chromosomes are aligned during metaphase I , but individual chromosomes are aligned during metaphase II .

D Homologous pairs of chromosomes are aligned during metaphase I , but individual chromosomes are aligned during metaphase II .

Australian dragon lizards have a ZW sex-determination system. The male genotype is homogametic (ZZ), and the female genotype is heterogametic (ZW). However, all eggs incubated at temperatures above 32°C tend to develop into females. Which of the following best explains how the development of phenotypic female Australian dragon lizards with a ZZ genotype occurs when incubation temperatures are above 32°C? A Lizard embryos with a ZZ genotype cannot develop at temperatures above 32°C. B At incubation temperatures above 32°C, Z chromosomes are mutated into W chromosomes. C At incubation temperatures above 32°C, crossing over transfers genes from the W chromosome to the Z chromosome, producing females. D Incubation temperatures above 32°C inhibit the genes on the Z chromosome that produce proteins necessary for male development.

D Incubation temperatures above 32°C inhibit the genes on the Z chromosome that produce proteins necessary for male development.

In anaphase I of meiosis, cohesion between the centromeres of sister chromatids is maintained while homologous chromosomes migrate to opposite poles of the cell along the meiotic spindle as represented in Figure 1. <insert image> A compound that prevents the separation of the homologous chromosomes in anaphase I is being studied. Which of the following questions can be best answered during this study? A Will the cells produced at the end of meiosis still be genetically identical to each other in the presence of this compound? B Will the long-term development of the individual be affected by this meiotic error? C When do the centrosomes start to move apart during meiosis I as compared to meiosis II? D Is there a pattern to the movement of homologous chromosomes in the presence of this compound?

D Is there a pattern to the movement of homologous chromosomes in the presence of this compound?

A spermatocyte produces the following four sperm cells. <Insert image> These cells are the result of nondisjunction during which of the following phases? A Interphase (G1 or G2) B Interphase (S) C Mitosis D Meiosis I E Meiosis II

D Meiosis I

Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes? A In mitosis, the chromosomes consist of a single chromatid, which is passed to two haploid daughter cells. In meiosis, the chromosomes consist of two chromatids during the first round of division and one chromatid during the second round of division, resulting in two haploid daughter cells. B In mitosis, synapsis of homologous chromosomes results in four haploid daughter cells after one division. In meiosis, synapsis of homologous chromosomes occurs during the second division and results in four diploid daughter cells. C Mitosis produces one identical daughter cell after one round of division. Meiosis has two rounds of division and doubles the number of chromosomes in the second round of division, producing four diploid cells. D Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

D Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

Figure 1 illustrates the X and Y chromosomes during meiosis I and meiosis II of normal spermatogenesis in a mammal species. <Insert table> If the normal spermatogenesis is disrupted, the gametes can have different chromosomes than expected. Which of the following is the most likely cause of one of the four gametes having two X chromosomes and one having neither an X nor a Y chromosome? A Nondisjunction of the chromosomes during meiosis I B Nondisjunction of both the X and Y chromosomes during meiosis II C Nondisjunction of the Y chromosome during meiosis II D Nondisjunction of the X chromosome during meiosis II

D Nondisjunction of the X chromosome during meiosis II

<insert table> The data above represent the results of three different crosses involving the inheritance of a gene that determines whether a certain organism is blue or white. Which of the following best explains the mechanism of inheritance of the gene? A The allele for white is an autosomal dominant allele because a 1:1 phenotype ratio of blue to white among both sexes is observed in cross 3. B The allele for blue is an autosomal dominant allele because an approximate 3:1 phenotype ratio of blue to white is observed in cross 1. C The allele for white is an X-linked dominant allele because no white females are produced in cross 1. D The allele for blue is an X-linked dominant allele because there are no blue male offspring in cross 2.

D The allele for blue is an X-linked dominant allele because there are no blue male offspring in cross 2.

In fruit flies, purple eyes and ebony body are traits that display autosomal recessive patterns of inheritance. In a genetics experiment, students cross wild-type flies with flies that have purple eyes and ebony bodies. The students observe that all the flies in the F1 generation have normal eyes and a normal body color. The students then allow the F1 flies to mate and produce an F2 generation. The students record observations about the flies in the F2 generation and use the data to perform a chi-square goodness-of-fit test for a model of independent assortment. The setup for the students' chi-square goodness-of-fit test is presented in Table 1. <insert table> The students choose a significance level of p=0.01. Which of the following statements best completes the next step of the chi-square goodness-of-fit test? A The calculated chi-square value is 2.11, and the critical value is 7.82. B The calculated chi-square value is 2.11, and the critical value is 11.35. C The calculated chi-square value is 10.48, and the critical value is 7.82. D The calculated chi-square value is 10.48, and the critical value is 11.35.

D The calculated chi-square value is 10.48, and the critical value is 11.35.

In corn plants, purple kernel color is dominant to yellow kernel color, and smooth kernels are dominant to wrinkled kernels. Researchers carried out a genetics experiment to investigate whether the genes controlling kernel color and kernel texture segregate independently. In their experiment, the researchers crossed two corn plants that were each heterozygous for both kernel color and kernel texture. The results of the experiment are presented in Table 1. <insert table> Using a significance level of p=0.05, which of the following statements best completes a chi-square goodness-of-fit test for a model of independent assortment? A The calculated chi-square value is 0.66, and the critical value is 0.05. The null hypothesis can be rejected. B The calculated chi-square value is 0.66, and the critical value is 3.84. The null hypothesis cannot be rejected. C The calculated chi-square value is 3.91, and the critical value is 5.99. The null hypothesis can be rejected. D The calculated chi-square value is 3.91, and the critical value is 7.82. The null hypothesis cannot be rejected.

D The calculated chi-square value is 3.91, and the critical value is 7.82. The null hypothesis cannot be rejected.

Figure 1 shows the inheritance of a particular genetic condition in three generations of one family. Which of the following best explains the observed pattern of inheritance? A The condition is passed randomly because of the independent assortment of chromosomes. B The condition is passed from fathers to sons via a Y-linked gene. C The condition is passed from mothers to sons via an X-linked gene. D The condition is passed from mothers to offspring via a mitochondrial gene.

D The condition is passed from mothers to offspring via a mitochondrial gene.

Rubber rabbitbrush plants display heritable variation in plant height and insect-induced gall formation. In a field study, researchers investigated the relationship between plant height and gall number for the rubber rabbitbrush plants in a natural population. The researchers used the data they collected to perform a chi-square test of independence. The null hypothesis for the chi-square test was that plant height and gall number are independent. The data for the chi-square test are presented in Table 1. <insert table> The researchers calculated a chi-square value of 29.25. If there are three degrees of freedom and the significance level is p=0.05, which of the following statements best completes the chi-square test? A The critical value is 0.05, and the null hypothesis cannot be rejected because the calculated chi-square value is greater than the critical value. B The critical value is 0.05, and the null hypothesis can be rejected because the calculated chi-square value is greater than the critical value. C The critical value is 7.82, and the null hypothesis cannot be rejected because the calculated chi-square value is greater than the critical value. D The critical value is 7.82, and the null hypothesis can be rejected because the calculated chi-square value is greater than the critical value.

D The critical value is 7.82, and the null hypothesis can be rejected because the calculated chi-square value is greater than the critical value.

Himalayan rabbits are a breed of rabbits with highly variable fur color. If genetically similar rabbits are raised in environments that have different temperature conditions, the rabbits can have different color patterns. Which of the following statements best explains how the fur color can be different in Himalayan rabbits raised under different temperature conditions? A The genotype does not contribute to coat color in Himalayan rabbits. B The phenotype determines the genotype of coat color in Himalayan rabbits. C Different environments cause specific mutations in the genes controlling pigment production. D The environment determines how the genotype is expressed.

D The environment determines how the genotype is expressed.

Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes? A The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells. B The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes. C The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell. D The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

D The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

In fruit flies, sepia eyes and ebony body are traits that display autosomal recessive patterns of inheritance. To investigate whether the traits are genetically linked, students cross wild-type flies with a line of flies that have sepia eyes and ebony bodies. The students observe that all the flies in the F1 generation have normal eyes and normal bodies. The students allow the flies in the F1 generation to mate and produce an F2 generation. The students then record observations for the flies in the F2 generation and use the data to perform a chi-square goodness-of-fit test for a model of independent assortment. The setup for the chi-square goodness-of-fit test is presented in Table 1. <insert table> The students calculate a chi-squared value of 92.86 and compare it with a critical value of 7.82. Which of the following best completes the chi-square goodness-of-fit test? A The null hypothesis cannot be rejected, and the students should conclude that the data fit a model of independent assortment. B The null hypothesis cannot be rejected, and the students should conclude that the data may have resulted from genetic linkage. C The null hypothesis can be rejected, and the students should conclude that the data fit a model of independent assortment. D The null hypothesis can be rejected, and the students should conclude that the data may have resulted from genetic linkage.

D The null hypothesis can be rejected, and the students should conclude that the data may have resulted from genetic linkage.

A scientist studying phenotypic variation in a species of butterfly observed that genetically identical caterpillars grown in similar cages but exposed to different colored lights developed into butterflies with differences in wing color and body size, as shown in Table 1. <insert table> Which of the following best explains the cause of the phenotypic variation observed in the butterflies? A Different mutations occurred in the caterpillars that were exposed to different colors of light. B The energy used to grow a larger body results in butterflies with lighter colored wings. C Individual caterpillars evolved adaptations to survive in each of the light conditions they were exposed to. D There was differential gene expression of wing color and body size in response to the colors of light the caterpillars were exposed to.

D There was differential gene expression of wing color and body size in response to the colors of light the caterpillars were exposed to.

R. C. Punnett conducted experiments on the inheritance of traits in the sweet pea, Lathyrus odoratus. In one experiment, he crossed two different true-breeding sweet pea plant strains, one with erect petals and long pollen, and the other with hooded petals and round pollen. All the offspring (F1 generation) had erect petals and long pollen (Figure 1). <insert image> Which of the following questions would be most useful to researchers trying to determine the role of meiosis in the F2 phenotypic frequencies? A What is the molecular mechanism underlying the dominance of erect petals and long pollen? B Which phenotypes give pea plants the highest level of fitness: erect or hooded petals and long or round pollen? C How do the phases of meiosis differ between sweet pea plants and other organisms? D What is the recombination frequency between the genes for petal shape and pollen shape?

D What is the recombination frequency between the genes for petal shape and pollen shape?