AP Biology Unit 5

In garden peas, a single gene controls stem length. The recessive allele (t) produces short stems when homozygous. The dominant allele (T) produces long stems. A short-stemmed plant is crossed with a heterozygous long-stemmed plant. Which of the following represents the expected phenotypes of the offspring and the ratio in which they will occur?

1 long-stemmed plant: 1 short-stemmed plant

A couple has 5 children, all sons. If the woman gives birth to a sixth child, what is the probability that the sixth child will be a son?

1/2

An allele on the X chromosome is responsible for the recessive trait of red-green color blindness in humans. The daughter of a woman who is color-blind has normal vision and marries a man who is color-blind. This couple has a son, what is the probability that the son will be color-blind?

1/2

If 2n = 48 for a particular cell, then the chromosome number in each cell after meiosis would be

24

In sheep, eye color is controlled by a single gene with two alleles. When a homozygous brown-eyed sheep is crossed with a homozygous green-eyed sheep, blue-eyed offspring are produced. If the blue-eyed sheep are mated with each other, what percent of their offspring will most likely have brown eyes?

25%

In the following human pedigree, squares represent males, circles represent females, and shaded symbols indicate individuals affected with a disorder.One of the affected males from the third generation has a child with a female who is a carrier. For the pedigree shown above, which of the following best expresses the probability that the couple's first son will be affected with the disorder?

50%

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?

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

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?

Autosomal recessive inheritance

Narrative for questions 34 - 35.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. Which of the following is probably the genotype of the dark, short-haired parent in cross I?

CCBB

The diagram below illustrates which of the following processes?

Crossing-over

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.

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

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?

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.

Which of the following best describes the cells that result from the process of meiosis in mammals?

They are genetically different from the parent cell.

Which of the following occurs in all species of living organisms and may lead to an increase in genetic variation?

Mutations in the genome

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?

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.

The tiny blue-eyed Mary flower is often one of the first flowers seen in the spring in some regions of the United States. The flower is normally blue, but sometimes a white or pink flower variation is found.The following data were obtained after several crosses. Parents F1 F2 Blue x white Blue 196 blue, 63 white Blue x pink Blue 149 blue, 52 pink Pink x white Blue 226 blue, 98 white, 77 pink Which of the following statements best explains the data?

Flower color is an inherited trait, and the F1 and F2 phenotypes of the flowers arising from the pink and white cross can best be explained by another gene product that influences the phenotypic expression.

A student in a biology class crossed a male Drosophila melanogaster having a gray body and long wings with a female D. melanogaster having a black body and apterous wings. The following distribution of traits was observed in the offspring. Phenotype Number of Offspring Gray body, long wings 42 Black body, apterous wings 41 Gray body, apterous wings 9 Black body, long wings 8 Which of the following is supported by the data?

Genes for the two traits are located close together on the same chromosome, and crossing over occurred between the two gene loci.

Which of the following best supports the claim that organisms of different domains share a common ancestor?

Glycolysis occurs in both prokaryotic cells and eukaryotic cells.

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 ?

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

The events listed below generally take place during meiosis. I. Synapsis occurs. II. Crossing-over is completed. III. Condensation of chromosomes begins. IV. Separation of homologous chromosomes begins. Which of the following is the correct sequence of these events?

III, I, II, IV

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?

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

Table I shows the results of breeding experiments to examine the inheritance of flower color (purple versus white) and pod shape (inflated versus constricted). For the crosses recorded in Table I, true-breeding parents were crossed to produce F1 offspring, which were then testcrossed to homozygous recessive individuals. Table II shows the results of computer-simulated crosses to model the inheritance of leaf shape (broad versus narrow) and flower color (purple versus white). Based on the data in Table I, which of the following best explains why there are no individuals with constricted pods in the F1 generation?

Inflated pod shape is dominant to constricted pod shape.

During prophase I replicated homologous chromosomes pair up and undergo synapsis.What testable question is generated regarding synapsis and genetic variability by Figure 1 ?

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?

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

Which of the following correctly describes the relationship of the dark-coat-color allele to the albino condition?

It is dominant.

A spermatocyte produces the following four sperm cells. n+1 n+1 n-1 n-1 These cells are the result of nondisjunction during which of the following phases?

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?

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

Gregor Mendel's pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked ona chromosome?

Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.

A blue-flowered African violet of unknown ancestry self-pollinated and produced 50 seeds. These seeds germinate and grow into flowering plants. Of these plants, 36 produce blue flowers and 14 produce pink flowers. What is the best explanation for the pink-flowered offspring?

Pink flower color is a trait recessive to blue flower color.

In Table II, the F1 offspring of the cross between broad-leaved, white-flowered plants with narrow- leaved, purple-flowered plants have a phenotype that differs from that of either parent. However, many testcross offspring have the same phenotype as one of the two plants in the parental cross, but relatively few testcross offspring have the same phenotype as the F1 offspring. Which of the following best explains the observation?

Recombination between the leaf-shape and flower-color genes resulted in chromosomes carrying a dominant allele of both genes.

Which of the following occurs in both meiosis and mitosis?

Separation of sister chromatids

Eye color in a particular strain of fly is influenced by one gene with two alleles: a dominant allele that results in red eyes and a recessive allele that results in sepia eyes.A red-eyed female from a true-breeding population is mated with a sepia-eyed male. The F1 offspring are all red-eyed. The F1 flies are allowed to interbreed, producing the following in the F2 generation.Females: 40 red eyes, 13 sepia eyesMales: 39 red eyes, 11 sepia eyesWhich of the following best describes the likely mode of inheritance for the eye-color gene?

The eye-color gene is likely autosomal because males and females have similar phenotype ratios.

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?

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

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?

The mother carries the allele for color blindness.

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?

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

Which of the following provides the best justification for an assumption that might have been used in the computer simulation (Table II) ?

The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and white- flowered plants had purple flowers

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?

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

In the pedigree below, squares represent males and circles represent females. Individuals who express a particular trait are represented by shaded figures.Which of the following patterns of inheritance best explains the transmission of the trait?

bruh idk

The pedigree in Figure 15.3 shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely

mitochondrial.

In Table I, the ratio of phenotypes in the offspring from the testcross with F1 plants that had purple flowers and inflated pods suggests that the genes for flower color and pod shape are located

on different chromosomes

In cats, black fur color is caused by an X-linked allele, the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

tortoiseshell females, black males

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?

translocation of SRY to an autosome of a 46, XX individual