Chapter 15 HW
A man with hemophilia (a recessive, sex-linked condition) has a daughter without hemophilia who marries a man without hemophilia. What is the probability of their daughter having hemophilia?
0
1. Humans are diploid and have 46 chromosomes (or two sets). How many sets of chromosomes are found in each human gamete? 2. Humans are diploid and have 46 chromosomes. How many chromosomes are found in each human gamete? 3. _____ is the process by which haploid gametes form a diploid zygote. 4. A particular diploid plant species has 48 chromosomes, or two sets. A mutation occurs and gametes with 48 chromosomes are produced. If self-fertilization occurs, the zygote will have _____ set(s) of chromosomes.
1. 1 2. 23 3. fertilization 4.
Use the following information to answer the question. A plantlike species on the hypothetical planet Pandora has three genetic traits: leaf color, controlled by gene L; a stem texture, controlled by gene S; and root length controlled by gene R. Each of the three genes has two alleles. The three genes are linked and recombine. A geneticist performed a testcross with an organism of that species that is heterozygous for the three traits. She recorded progeny with the following phenotypic distribution: lSR-14 ; lSr-0 ; lsR-32 ; lsr-440 ; LsR-0 ; Lsr-16 ; LSr-28 ; LSR-470 ; Total-1,000 1. Assuming that genetic inheritance for this hypothetical plant functions the same as on Earth, the parents in this cross most likely have the same phenotypes as which of the following progeny? 2. Which of the progeny phenotypes will require recombination between genes L and S? 3. What is the approximate distance between genes L and S?
1. 4 and 8 2. lsR, lSr, LsR, Lsr 3. 3 map units
Red-green color blindness is due to an X-linked recessive allele in humans. A widow's peak (a hairline that comes to a peak in the middle of the forehead) is due to an autosomal dominant allele. Consider the following family history: A man with a widow's peak and normal color vision marries a color-blind woman with a straight hairline. The man's father had a straight hairline, as did both of the woman's parents. Use the family history to make predictions about the couple's children.
1. if the couple has a child, what is the chance that it will be a son witth a widow's peak? 1/4 2. What is the chance that any son the couple has will be color blind with a straight hairline? 1/2 3. What is the chance that any son the couple has will be color blind with a widow's peak? 0 4. Suppose the couple had a daughter with normal color vision and a widow's peak. What is the chance she is heterozygous for both genes? 1
1. Which of these terms applies to an organism with extra sets of chromosomes? 2. Mutant tetraploid plants _____ 3. Most polyploid plants arise as a result of _____.
1. polyploid 2. are unable to interbreed with a diploid plant 3. hybridization
1. In the P generation, a true-breeding pea plant with genotype YYRR is crossed with a true-breeding plant with genotype _____. 2. The resulting offspring--the F1 generation--have genotype _____. 3. According to Mendel's law of independent assortment, the alleles for seed color and seed shape are transmitted into gametes in _____. 4. This means that the F1 generation makes gametes with the following genotypes: _____. 5. At fertilization, two gametes (egg and sperm) come together. The resulting F2 generation exhibits _____ different phenotypes in the ratio of _____.
1. yyrr 2. YyRr 3. all possible combinations 4. YR, Yr, yR, yr 5. four, 9 to 3 to 3 to 1
A man with hemophilia (a recessive, sex-linked condition) has a daughter without hemophilia who marries a man without hemophilia. If they have four sons, what is the probability that all will be affected?
1/16
A man with hemophilia (a recessive, sex-linked condition) has a daughter without hemophilia who marries a man without hemophilia. What is the probability of their son having hemophilia?
1/2
For tall heterozygotes with antennae, the offspring are: tall/antennae: 46 dwarf/antennae: 7 dwarf/no antennae: 42 tall/no antennae: 5 Calculate the recombination frequency between T and A.
12% ((5+7)/100)*100%
A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F1 had red fruit and yellow flowers. F1 plants were testcrossed (crossing them to homozygous recessive individuals), and the following offspring were obtained: Red fruit and yellow flowers-41 Red fruit and white flowers-7 Golden fruit and yellow flowers-8 Golden fruit and white flowers-44 How many map units separate these genes?
15 ((7+8)/100)*100
Scientists do a testcross using heterozygotes for height and nose shape. The offspring are: tall/upturned snout: 41 dwarf/upturned snout: 8 dwarf/downturned snout: 43 tall/downturned snout: 8 Calculate the recombination frequency between T and S.
16% ((8+8)/100)*100%
A wild-type fruit fly (heterozygous for gray body color and normal wings) is mated with a black fly with vestigial wings. The offspring have the following phenotypic distribution: wild-type: 778 ; black vestigial: 785 ; black normal: 158 ; gray vestigial: 162 What is the recombination frequency between these genes for body color and wing size?
17% (recombinant = 158+162 = 320, total = 1883, recombination frequency = (320/1882)*100%
Two genes of a flower, one controlling blue (BB) versus white (bb) petals and the other controlling round (RR) versus oval (rr) stamens, are linked and are 10 map units apart. You cross a homozygous blue/oval plant with a homozygous white/round plant. The resulting F1 progeny are crossed with homozygous white/oval plants, and 1,000 offspring plants are obtained. How many F2 plants of each of the four phenotypes do you expect? **image** _____ blue/oval : _____ white/round : _____ blue/round : _____ white/oval
450: 450: 50: 50
For heterozygotes with antennae and an upturned snout, the offspring are: antennae/upturned snout: 47 antennae/downturned snout: 2 no antennae/downturned snout: 48 no antennae/upturned snout: 3 Calculate the recombination frequency between A and S.
5% ((3+2)/100)*100%
Assume that genes AA and BB are 50 map units apart on the same chromosome. An animal heterozygous at both loci is crossed with one that is homozygous recessive at both loci. What percentage of the offspring will show recombinant phenotypes resulting from crossovers?
50%
A wild-type fruit fly (heterozygous for gray body color and red eyes) is mated with a black fruit fly with purple eyes. The offspring are: wild-type: 721 black/purple: 751 gray/purple: 49 black/red: 45 What is the recombination frequency between these genes for body color and eye color?
6% ((49+45)/1566)*100%
The inheritance of eye color in Drosophila is controlled by genes on each of the fly's four chromosome pairs. One eye-color gene is on the fly's X chromosome, so the trait is inherited in a sex-linked manner. For this sex-linked trait, the wild-type (brick red) allele is dominant over the mutant vermilion (bright red) allele. A homozygous wild-type female fly is mated with a vermilion male fly. X+X+ × XvY Predict the eye colors of F1 and F2 generations. (Assume that the F1 flies are allowed to interbreed to produce the F2 generation.)
All wild type: F1 females, F1 males, F2 females 1/2 wild type, 1/2 vermillion: F2 males
You now know that inheritance of eye color in fruit flies is sex-linked: The gene encoding eye color is located on the X chromosome, and there is no corresponding gene on the Y chromosome. How would the inheritance pattern differ if the gene for eye color were instead located on an autosome (a non-sex chromosome)? Recall that for autosomes, both chromosomes of a homologous pair carry the same genes in the same locations. Suppose that a geneticist crossed a large number of white-eyed females with red-eyed males. Consider two separate cases: Case 1: Eye color exhibits sex-linked inheritance. Case 2: Eye color exhibits autosomal (non-sex-linked) inheritance. (Note: In this case, assume that the red-eyed males are homozygous.)
Case 1: Eye color exhibits sex-linked inheritance 1. If there were 100 female offspring, 100 would have red eyes and 0 would have white eyes. 2. If there were 100 male offspring, 0 would have red eyes and 100 would have white eyes. Case 2: Eye color exhibits autosomal (non-sex-linked) inheritance 3. If there were 100 female offspring, 100 would have red eyes and 0 would have white eyes. 4. If there were 100 male offspring, 100 would have red eyes and 0 would have white eyes.
You are investigating the inheritance of two rare conditions (A and B) in an extended family of thoroughbred racehorses. You have constructed the following pedigree for these conditions. **image**
Condition A: autosomal recessive Condition B: x-linked recessive
In the figure below, you can see Mendel's experiment again, this time superimposed on the events of meiosis and fertilization. How does chromosomal inheritance during meiosis explain Mendel's law of independent assortment?
Metaphase I: two chromosome arrangements equally probable at metaphase plate. each cell has the genotype YyRr Anaphase I: homologous chromosomes separate. Y may sort with R or r, y may sort with R or r Telophase II: sister chromatids have separated. four types of gametes produced: YR, Yr, yR, and yr Fertilization: chromosomes in haploid gametes combine in diploid zygote. four phenotypes produced in F2 generation in 9:3:3:1 ratio
A phenotypically normal couple seeks genetic counseling because the man's karyotype showed that his chromosomes had a reciprocal translocation between chromosomes 4 and 12. Because the translocation is reciprocal there was no genetic information lost and he is healthy; however, he and his wife want to know the probability that his sperm cells will be abnormal. Which fraction of his sperm cells is predicted to carry at least one chromosome with a translocation? a. three-fourth will have at least one chromosome with a translocation; the other 1/4 will carry normal chromosomes 4 and 12 b. all will carry the same translocation as the father c. none will carry the translocation d. one-half will have the father's translocation and 1/2 will carry normal chromosomes 4 and 12
a
If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)? a. n + 1; n + 1; n - 1; n - 1 b. n + 1; n - 1; n; n c. n + 1; n + 1; n; n d. n + 1; n - 1; n - 1; n - 1
a
In humans, clear sex differentiation does not occur at fertilization. It becomes evident after the second month of gestation. Which of the following statements describes the first event of sex differentiation in human embryos? a. activation of SRY in male embryos and masculinization of the gonads b. production of estrogens in female embryos c. production of testosterone in male embryos d. activation of SRY in females and feminization of the gonads
a
Is the recombination frequency consistent with the results of the experiment in this figure? **image** a. Yes, because a distance between the very same two genes would not change from one experiment to another. b. No, because a distance between the very same two genes may change in different flies.
a
Of the following chromosomal abnormalities, which type is most likely to be viable in humans? a. Trisomy b. Triploidy c. Monosomy d. Haploidy
a
Select the correct statement(s) about sex determination in animals. Select all that apply. a. The mechanism of sex determination varies with different animal species. b. In all animals, males are XY and females are XX. c. In all animals, males have the SRY gene and females lack this gene.
a
Which of the following reasons explains why map units on a chromosome linkage map are not reliable measures of physical distances? a. The frequency of crossing over varies along the length of the chromosome. b. The gene order on the chromosomes is slightly different in every individual. c. The relationship between recombination frequency and map units is different in every individual. d. Physical distances between genes change during the course of the cell cycle.
a
Which of the following results in a situation in which the chromosome number is either 2n+1 or 2n−1? a. aneuploidy b. polyploidy c. inversion d. gene linkage e. methylation
a
Which of the following statements correctly describes the chromosome theory of inheritance as it was understood in the early 20th century? a. Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis. b. Individuals inherit particular chromosomes attached to genes. c. Natural selection acts on certain chromosome combinations rather than on genes. d. No more than a single pair of chromosomes can be found in a healthy normal cell.
a
Which of the following statements correctly describes what happens to a chromosome after a nonreciprocal translocation? a. a chromosome transfers a fragment but receives none in return b. a Philadelphia chromosome is generated c. a duplication of part of the chromosome occurs d. nondisjunction of pairs of homologous occurs
a
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation? a. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I. b. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs. c. Sister chromatids separate during anaphase II.
a
A man with normal vision who is a dwarf due to achondroplasia has children with a woman with colorblindness who is of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their daughters are expected to be color-blind with achondroplasia? a. 1/4 b. 0 c. 3/4 d. 1/2
b
A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind has children with a color-blind male. What is the probability that this couple's first son will be color blind? a. 2/3 b. 1/2 c. 1/4 d. 3/4
b
A testcross performed with F1 dihybrid flies results in more parental-type offspring than recombinant-type offspring. Which of the following statements best explains this result? a. Recombination did not occur in the cell during meiosis. b. The two genes are linked on the same chromosome. c. Both of the characters are controlled by more than one gene. d. The two genes are linked but on different chromosomes.
b
Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions that could result in which of the following events? a. a decrease in mitotic frequency b. expression of genes that lead to inappropriate cell division c. an increase in nondisjunction d. failure of the cancer cells to multiply
b
Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients' muscles weaken over time because they have a lack or decreased levels of dystrophin, a muscle protein. Which of the following correctly predicts the probability of muscular dystrophy in female children? a. Females can never have this condition. b. One-half of the daughters of an affected man and a carrier woman would have this condition. c. One-half of the daughters of an unaffected man and a carrier woman would have this condition. d. One-fourth of the daughters of an affected man would have this condition.
b
Glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as an X-linked recessive allele in humans. A woman whose father had G6PD is planning a family with a man who has no history of the disease. What proportion of their sons are expected to have the disease? a. 100% b. 1/2 c. 1/4 d. 0
b
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred? a. A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell. b. A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell. c. No error occurred; these are normal gametes. d. A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
b
Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females? a. Males would display this disorder with greater frequency than females. b. Females would display this disorder with greater frequency than males. c. Males and females would display this disorder with equal frequency.
b
In Drosophila melanogaster, wing-size and body-color genes are linked. Vestigial wings and black body color are both recessive traits. A researcher crossed black-bodied, normal-winged females and gray-bodied, vestigial-winged males. The F1 were all gray bodied, normal winged. A test cross was performed with F1 females. The researcher calculated a map distance of 17 map units. Which of the following information is correct about the testcross progeny? a. black-bodied, vestigial-winged flies = 17% of the total b. black-bodied, normal-winged flies plus gray-bodied, vestigial-winged flies = 17% of the total c. black-bodied, normal-winged flies = 17% of the total d. gray-bodied, normal-winged flies plus black-bodied, vestigial-winged flies = 17% of the total
b
In humans, what determines the sex of offspring, and why? a. The chromosome contribution from both parents determines sex, because the offspring uses all the parents' chromosomes. b. The male gamete determines sex, because each male gamete can contribute either an X or a Y chromosome. c. The female gamete determines sex, because only the female gamete provides cytoplasm to the zygote. d. The female gamete determines sex, because only the female gametes can have one of two functional sex chromosomes. e. The male determines sex, because the sperm can fertilize either a female egg or a male egg.
b
What observable cellular process explains Mendel's Law of Segregation? a. the behavior of sex-linked genes b. homologous chromosomes separating during meiosis I c. homologous chromosomes separating during meiosis II d. the replication of DNA e. sister chromatids separating during mitosis
b
Which of the following individuals will inherit an X-linked allele from a male parent who carries the allele? a. all of his children b. all of his daughters c. half of his daughters d. all of his sons
b
Which of the following statements regarding gene linkage is correct? a. Unlinked genes do not follow the law of equal segregation. b. The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. c. Linked genes are found on different chromosomes. d. The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.
b
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of independent assortment? a. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I. b. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs. c. Sister chromatids separate during anaphase II.
b
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure. Based on this information, what is the order of these genes on a chromosome map?
b-rb-cn-vg
A recombination frequency of 50% indicates ________. a. all of the offspring have combinations of traits that match one of the two parents b. the genes are located on sex chromosomes c. the two genes are likely to be located on different chromosomes d. the two genes are five map units apart
c
Cinnabar eye color is an X-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a male having wild-type, red eyes, what percent of the F1 males will have cinnabar eyes? a. 25% b. 50% c. 100% d. 0%
c
Gregor Mendel set up a dihybrid cross with one pea plant from the parental generation (P) producing round yellow peas and the other pea plant producing wrinkled green peas. The F2 generation included 315 plants producing round yellow peas, 108 with round green peas, 101 with wrinkled yellow peas, and 32 with wrinkled green peas. How would these results have differed if pea shape and pea color had been linked genes, located close together on the same chromosome? a. The F2 generation would have included a higher percentage of pea plants producing yellow peas. b. The F2 generation would have included a lower percentage of pea plants producing wrinkled, green peas. c. The F2 generation would have included a higher percentage of pea plants producing round, yellow peas.
c
If cell Q enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis? a. Half of the gametes descended from cell Q will be n + 1, and half will be n - 1. b. Two of the four gametes descended from cell Q will be haploid, and two will be diploid. c. One-quarter of the gametes descended from cell Q will be n + 1, one-quarter will be n - 1, and half will be n. d. All the gametes descended from cell Q will be diploid.
c
In cats, an X-linked locus is responsible for fur color. There are two known alleles at this locus. One results in black fur color; the other results in orange fur color. A heterozygote animal has patches of orange and black fur (tortoiseshell). Which coat color phenotypes are expected from the cross of a black female and an orange male? a. tortoiseshell females; tortoiseshell males b. orange females; black males c. tortoiseshell females; black males d. black females; orange males
c
Male sex determination in mammals is in large part due to the SRY gene found on the Y chromosome. Which of the following scenarios will result in a person with an XX karyotype developing a male phenotype? a. the loss of the SRY gene from an autosome during gamete formation b. the presence of an extra autosomal chromosome after fertilization c. translocation of SRY to an X chromosome during gamete formation d. nondisjunction of the X chromosome during meiosis
c
Males are more often affected by X-linked traits than are females because ________. a. imprinting is more likely to occur on X chromosomes inherited from the mother than on Y chromosomes inherited from the father b. X chromosomes in males generally have more mutations than X chromosomes in females c. males are hemizygous genes on the X chromosomes d. X inactivation occurring in male effectively shuts down expression of any X chromosome genes
c
Recombination between linked genes is an adaptive advantage within a changing environment because ________. a. recombination ensures each offspring will have an increased chance of survival b. recombination must occur or genes will not assort independently c. new allele combinations increase diversity in a population d. recombination allows genes to be shuffled along chromosomes
c
Red-green color blindness is an X-linked recessive trait in humans. Two people with normal color vision have a son with colorblindness. Given this information, the genotypes of the parents are ________. a. XNXN and XnY b. XNXN and XNY c. XNXn and XNY d. XnXn and XnY
c
The χ2χ2 value means nothing on its own--it is used to find the probability that, assuming the hypothesis is true, the observed data set could have resulted from random fluctuations. A low probability suggests the observed data is not consistent with the hypothesis, and thus the hypothesis should be rejected. What is the hypothesis that you are testing? a. The two genes are linked and are assorting together, leading to a 1:1:1:1 ratio of phenotypes in the offspring. b. The two genes are linked and are assorting together, leading to a ratio of phenotypes in the offspring that deviates significantly from 1:1:1:1. c. The two genes are unlinked and are assorting independently, leading to a 1:1:1:1 ratio of phenotypes in the offspring. d. The two genes are unlinked and are assorting independently, leading to a 1:1:0:0 ratio of phenotypes in the offspring.
c
Use the following information to answer the question. male, wild-123 male, yellow-116 female, wild-240 In a Drosophila experiment, a homozygous wild-type female was crossed with a yellow-bodied male. All of the resulting F1 flies were phenotypically wild type. Crossing the F1 flies resulted in F2 flies having the characteristics shown in the figure. Which of the following statements best describes the location of the yellow body locus? a. It is on an autosome. b. It is Y-linked. c. It is X-linked. d. It is inherited by X inactivation.
c
Use the following information to answer the question. male, wild-123 male, yellow-116 female, wild-240 In a Drosophila experiment, a homozygous wild-type female was crossed with a yellow-bodied male. All of the resulting F1 flies were phenotypically wild type. Crossing the F1 flies resulted in F2 flies having the characteristics shown in the figure. Which of the following statements best describes the yellow body allele? a. It is codominant. b. It is dominant. c. It is recessive. d. It is incompletely dominant.
c
Use the following map of four genes on a chromosome to answer the question. When collecting data from genetic crosses which gene pair is most likely to show the highest frequency of recombination? A---(5)---W--(3)--E-----(12)-----G a. A and W b. E and G c. A and G d. A and E
c
What is a nondisjunction? a. An error in which a diploid cell or organism has an extra chromosome of one type, producing a chromosome number of 2n + 1 b. An error in which a diploid cell or organism lacks a chromosome of one type, producing a chromosome number of 2n - 1 c. An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell d. None of the above
c
What is the correct order of the three linked genes? a. A−T−S b. T−S−A c. T−A−S
c
What name is given to the most common phenotype in a natural population? a. locus b. autosome c. wild type d. genotype e. mutant phenotype
c
When Thomas Hunt Morgan crossed red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies, but all the white-eyed flies were male. Which of these best explains Morgan's result? a. The gene involved is located on the Y chromosome. b. The gene involved is located on an autosome, but only in males. c. The gene involved is located on the X chromosome. d. Other male-specific factors influence eye color in flies.
c
Which of the following events will result in recombination between linked genes? a. Linked genes traveling together at anaphase. b. Nonhomologous chromosomes breaking and then rejoining with one another. c. Crossovers between genes resulting in chromosomal exchange. d. Incomplete independent assortment.
c
Without knowing these genes are on the same chromosome, how would you interpret the results of this cross? a. You would interpret the results to mean that the genes are sex-linked. b. You would interpret the results to mean that the genes are on the same chromosome but less than 50 map units apart. c. You would interpret the results to mean that the genes are not on the same chromosome and are unlinked. d. The results cannot be interpreted otherwise.
c
A man with normal vision who is a dwarf due to achondroplasia has children with a woman who is colorblind and of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons are expected to be color blind and of normal height? a. 0 b. 1/4 c. all d. 1/2
d
A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results? a. Fifty percent of the females will have red eyes. b. Twenty-five percent of the females will have white eyes. c. None of the females will have red eyes. d. None of the females will have white eyes. e. Twenty-five percent of the females will have red eyes.
d
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred? a. No error occurred; these are normal gametes. b. A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell. c. A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell. d. A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
d
In birds, sex is determined by ZW chromosome inheritance. Males are ZZ and females are ZW. Within pigeon populations there is a recessive, Z-linked allele that is lethal in embryos. What is the expected sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a wildtype female? a. 1:1 male to female b. 3:1 male to female c. 1:2 male to female d. 2:1 male to female
d
Now, suppose that the three tomato genes from Part A did not assort independently, but instead were linked to one another on the same chromosome. Would you expect the phenotypic ratio in the offspring to change? If so, how? Which statement best predicts the results of the cross MmDdPp x mmddpp assuming that all three genes are linked? a. Lack of independent assortment means that you cannot predict the frequencies of phenotypes in the offspring. b. Only the parental phenotypes could possibly occur in the offspring. c. All eight possible phenotypes would occur in equal numbers in the offspring (1:1:1:1:1:1:1:1). d. All eight possible phenotypes could occur, but a greater proportion of the offspring would have the parental phenotypes.
d
The SRY gene is best described as ________. a. an autosomal gene that whose product is required for the expression of genes on the X chromosome b. a gene present on the X chromosome whose product regulates female development c. an autosomal gene whose product is required for the expression of genes on the Y chromosome d. a gene present on the Y chromosome whose product regulates male development
d
The recombination frequency between the genes for the body color (b+b+ = gray; bb = black) and the wing size (vg+vg+ = normal; vgvg = vestigial wings) is 17%%. What fruit flies (genotypes and phenotypes) would you mate to determine the order of the body color, wing size, and eye color genes on the chromosome? a. wild-type heterozygous for the gray body and red eyes × recessive homozygous for the black body and purple eyes b. wild-type heterozygous for the gray body and normal wings × recessive homozygous for the black body and vestigial wings c. wild-type heterozygous for the normal wings and red eyes × wild-type heterozygous for the normal wings and red eyes d. wild-type heterozygous for the normal wings and red eyes × recessive homozygous for the vestigial wings and purple eyes
d
What kind of cell results when a diploid and a haploid gamete fuse during fertilization? a. A trisomic cell b. A monosomic cell c. A monoploid cell d. A triploid cell
d
When can nondisjunction occur? Choose the best answer. a. In meiosis, when sister chromatids fail to separate b. In meiosis, when homologous chromosomes fail to separate c. In mitosis, when sister chromatids fail to separate d. All three answers are correct.
d
Which of the following events results in X-inactivation in female mammals? a. activation of the BARR gene on one X chromosome, which then becomes inactive b. inactivation of the XIST gene on the X chromosome derived from the male parent c. attachment of methyl (-CH3) groups to the X chromosome that will remain active d. activation of the XIST gene on the X chromosome that will become the Barr body
d
Which of the following is true of an X-linked gene, but not of a Y-linked gene? a. it is only expressed in female offspring b. it is expressed in half of the cells of either male or female c. it does not segregate like other genes d. the gene is present in both males and females e. sister chromatids separate during mitosis
d
Which of the following phrases correctly defines one genetic map unit? a. the physical distance between any two linked genes b. the recombination frequency between two independently assorting genes c. one nanometer of distance between two genes d. the physical distance between two genes that results in a 1% frequency of recombination
d
Which of the following statements explains the observation that closely linked genes are typically inherited together? a. The genes undergo nondisjunction in either meiosis I or meiosis II. b. Alleles are paired together during meiosis. c. Crossing over between identical copies can't be detected because it regenerates the original genotype. d. The genes are located close together on the same chromosome.
d
Which syndrome is characterized by the XO chromosome abnormality? a. Trisomy X b. Down syndrome c. Klinefelter syndrome d. Turner syndrome
d
You design Drosophila crosses to provide recombination data for gene aa, which is located on the chromosome shown in the following figure. Gene aa has recombination frequencies of 14% with the vestigial wing locus and 26% with the brown eye locus. Approximately where is aa located along the chromosome relative to these two loci? **image** a. equidistant between the vestigial wing locus and the brown eye locus b. about one-third of the distance from the vestigial wing locus to the cinnabar eye locus c. about two-thirds of the distance from the vestigial wing locus to the brown eye locus d. about one-third of the distance from the vestigial wing locus to the brown eye locus
d
Consider the following family history: -Bob has a genetic condition that affects his skin. -Bob's wife, Eleanor, has normal skin. No one in Eleanor's family has ever had the skin condition. -Bob and Eleanor have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their daughters have the same skin condition as Bob. Based on Bob and Eleanor's family history, what inheritance pattern does the skin condition most likely follow? a. X-linked recessive b. Y-linked c. autosomal recessive d. autosomal dominant e. X-linked dominant
e
In general, what does the frequency with which crossing over occurs between two linked genes depend on? a. the characters the genes code for b. whether the genes are on the X or some other chromosome c. whether the genes are dominant or recessive d. the phase of meiosis in which the crossing over occurs e. how far apart the two genes are on the chromosome
e
Which of the following is true of an X-linked gene, but not of a Y-linked gene? See Concept 15.2 (Page) a. It does not segregate like other genes. b. It is expressed in half of the cells of either male or female. c. It is only expressed in female offspring. d. Sister chromatids separate during mitosis. e. The gene is present in both males and females.
e
Suppose that you perform the cross discussed in Part B: MmDdPp x mmddpp. You plant 1000 tomato seeds resulting from the cross, and get the following results:Use the data to complete the linkage map below. Be careful and be sure that you determine which gene is in the middle before calclating map distances!Drag the labels onto the chromosome diagram to identify the locations of and distances between the genes. Use the blue labels and blue targets for the genes; use the white labels and white targets for the distances. Gene m has already been placed on the linkage map.
first image
A wild-type tomato plant (Plant 1) is homozygous dominant for three traits: solid leaves (MM), normal height (DD), and smooth skin (PP). Another tomato plant (Plant 2) is homozygous recessive for the same three traits: mottled leaves (mm), dwarf height (dd), and peach skin (pp). In a cross between these two plants (MMDDPP x mmddpp), all offspring in the F1 generation are wild type and heterozygous for all three traits (MmDdPp). Now suppose you perform a testcross on one of the F1 plants (MmDdPp x mmddpp). The F2 generation can include plants with these eight possible phenotypes: solid, normal, smooth solid, normal, peach solid, dwarf, smooth solid, dwarf, peach mottled, normal, smooth mottled, normal, peach mottled, dwarf, smooth mottled, dwarf, peach
image
In cosmos plants, purple stem (A) is dominant to green stem (a), and short petals (B) is dominant to long petals (b). In a simulated cross, AABB plants were crossed with aabb plants to generate F1 dihybrids (AaBb), which were then test crossed (AaBb X aabb). 900 offspring plants were scored for stem color and flower petal length. The hypothesis that the two genes are unlinked predicts the offspring phenotypic ratio will be 1:1:1:1.
image
Label the genes on the chromosomes in the wild-type and black parents.
image
The eight gamete classes for the testcross in Part B are shown in the table below. For each gamete, determine if it represents a recombinant (REC) or nonrecombinant (nonREC) gamete for the three pairs of loci: apricot and blunt (the A-B column), blunt and crimson (the B-C column), and apricot and crimson (the A-C column).
image
You have also identified a third recessive mutation that you call crimson. Wasps homozygous for crimson have a red abdomen. (Wild-type abdomens are yellow.)You make pure-breeding crimson (cc) and triple-mutant (apricot, blunt, crimson) lines. To map the three loci, you perform a trihybrid (three-point) testcross: You first cross crimson wasps with (apricot, blunt) wasps to make an F1, and then you testcross the F1 with the triple-mutant line. The F2 has eight phenotypes. For each F2 phenotype, determine the genotype of the gamete it received from the F1 trihybrid.
image
You have screened for several new recessive mutations in a species of wasp. Wasps homozygous for apricot (aa) have pale orange eyes. (Wild-type eyes are brown.) Wasps homozygous for blunt (bb) have short wings. (Wild-type wings are long.) You make a pure-breeding double-mutant (apricot, blunt) line and cross it with wild-type wasps. The F1 is wild-type in appearance. You testcross the F1 dihybrids with the double-mutant line (the "tester" genotype) and obtain four phenotypes in the F2: wild type apricot, blunt apricot blunt Determine the following for each F2 phenotype: the haploid genotype of the gamete it received from the F1 dihybrid its full diploid genotype whether the gamete it received from the F1 dihybrid was recombinant (REC) or nonrecombinant (nonREC).
image
Suppose that you perform the cross discussed in Part B: MmDdPp x mmddpp. You plant 1000 tomato seeds resulting from the cross, and get the following results:Use the data to complete the linkage map below. Be careful and be sure that you determine which gene is in the middle before calclating map distances!Drag the labels onto the chromosome diagram to identify the locations of and distances between the genes. Use the blue labels and blue targets for the genes; use the white labels and white targets for the distances. Gene m has already been placed on the linkage map.
second image
The chromosomal alteration that results from a chromosome fragment joined to a nonhomologous chromosome is called a ________.
translocation
