AP Biology Unit 5 Test

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.

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?

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. 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.

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. 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.

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.

An experiment was performed to determine the mode of inheritance of two mouse genes, one for fur color and one for fur length. It is known that black fur (B) is dominant over white fur (b) and that long fur (L) is dominant over short fur (l). To determine how the genes are inherited, a cross was performed between two true-breeding mice, one with long black fur and one with short white fur. Their progeny, the F1 generation, all had long black fur. Five F1 male-female pairs were then crossed with one another. The F2 generation phenotypes for each cross are shown in Table 1. Which of the following is the mean number per cross of F2 generation offspring that are the result of crossing over?

B. 2.2

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. Based on the inheritance pattern shown in Figure 1, which of the following best predicts the nature of the original mutation?

B. A recessive mutation on a somatic chromosome

Antibiotics can be used to kill the specific pathogenic bacterium, Mycobacterium tuberculosis, that causes tuberculosis. The appearance of antibiotic-resistant strains has made it more difficult to cure M. tuberculosis infections. These antibiotic-resistant bacteria survive and pass on the genes to their offspring, making the resistant phenotype more common in the population. DNA analysis indicates that the genes for antibiotic resistance are not normally present in bacterial chromosomal DNA. Which of the following statements best explains how the genes for antibiotic resistance can be transmitted between bacteria without the exchange of bacterial chromosomal DNA?

B. The genes for antibiotic resistance are located on a plasmid that can be passed to neighboring bacteria.

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. 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?

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. Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis I?

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.

A model showing two possible arrangements of chromosomes during meiosis is shown in Figure 1. Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1?

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

Figure 1 illustrates the X and Y chromosomes during meiosis I and meiosis II of normal spermatogenesis in a mammal species. 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?

D. Nondisjunction of the X chromosome during meiosis II

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. 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?

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

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. How would the extra chromosome affect the male offspring produced by the gamete?

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

Provide reasoning to justify your prediction.

The response indicates that the plants will inherit a functional gene in the pollen from the wild-type green plant. Depending on the amount of the gene's encoded protein that is needed for chlorophyll production, the leaves might be a paler green, but they will be all green.

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. Which of the following is the mean number of male offspring produced by the three crosses?

D. 9

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?

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

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?

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

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. 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?

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

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?

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.

A gene that influences coat color in domestic cats is located on the X chromosome. A female cat that is heterozygous for the gene (XBXO) has a calico-colored coat. In a genetics experiment, researchers mate a calico-colored female cat (XBXO) with an orange-colored male cat (XOY) to produce an F1 generation. The researchers record observations for the cats in the F1 generation and plan to use the data to perform a chi-square goodness-of-fit test for a model of X-linked inheritance. The data for the chi-square goodness-of-fit test are presented in Table 1. The researchers calculate a chi-square value of 4.6 and choose a significance level of p = 0.05. Which of the following statements best completes the chi-square goodness-of-fit test?

D. The null hypothesis cannot be rejected because the chi-square value is less than the critical value.

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. Which of the following best explains the cause of the phenotypic variation observed in the butterflies?

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

Ovules produced by an entirely green plant contain a rare mutation in a nuclear gene that is involved in chlorophyll synthesis, and the gene encodes a nonfunctional protein. Predict the most likely color of the leaves on plants that are produced when these ovules are fertilized by pollen from a wild-type green plant.

I predict that the leaves on the plants will most likely have a green color. The response indicates that the leaves will probably be all green.

In plants, genes involved in chlorophyll synthesis are located in both the nucleus and chloroplasts. Some variegated plants (with both green and white leaves and shoots) have mutations that prevent them from synthesizing chlorophyll throughout their leaves. In an effort to understand the genetics underlying chlorophyll synthesis, scientists performed the crosses shown in Figure 1. Describe how genetic information is carried in chloroplasts and mitochondria.

In a cell, there are several organelles that contain genetic information. Besides the nucleus, mitochondria and chloroplasts also develop their own genomes and genetic system. The DNA molecules found in mitochondria and chloroplasts are small and circular, similar to the DNA of a typical bacterium. There are usually many copies of DNA in a single mitochondrion or chloroplast. These organelles and the genes they carry are randomly distributed to daughter cells during mitosis and meiosis, so the organelles that happen to be on opposite sides of the cell will end up in different daughter cells. Non-nuclear DNA is also often inherited from one parent only, either the female or male, but not both. The response indicates that chloroplasts and mitochondria contain DNA and RNA.

Explain how the inheritance pattern shown in Figure 1 supports a role for chloroplast genes in the production of chlorophyll in the variegated plants.

The result of the experiment identifies that the color of the ovule parent prevails and assigns the color of the offspring. The female parental branches that were all-green or all-white had children of all-green or all-white, respectively. The female parental branches that were variegated resulted in all three types of offspring. It is evident that the chloroplast shows maternal (pollen plant) inheritance. The branch that is pure green will produce ovules with green chloroplasts that will give rise to an all-green offspring. Thus, an all-white branch will have offspring with ovules with an exclusive content of white chloroplasts and will give rise to a pure white offspring. If a branch is variegated, it is combined, some with only functional chloroplasts, some with only non-functional chloroplasts, and some with a mixture of chloroplasts. All three types of cells can give rise to ovules, leading to green offspring, white offspring, and variegated offspring. The response indicates that chloroplasts are transmitted to progeny only from the female parent in the ovule and that the progeny produced always match or can be produced from the ovule used in the cross.