Biology Ch 15

PART D: What kind of cell results when a diploid and a haploid gamete fuse during fertilization?

A triploid cell

PART B: When can a nondisjunction occur?

All three answers are correct

PART A: What is a nondisjunction?

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction?

An inversion

A cell goes through S phase, meiosis I, and cytokinesis. As the daughter cells are beginning meiosis II, which of the following is an appropriate description of the contents of each cell?

Each has half the chromosomes and the same amount of DNA as the original cell.

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?

Females would display this disorder with greater frequency than males.

PART C: _____ is the process by which haploid gametes form a diploid zygote.

Fertilization

PART C Down syndrome is caused by trisomy 21, the presence of three copies of chromosome 21. The extra copy usually results from nondisjunction during meiosis. In some cases, however, the extra copy results from a translocation of most of chromosome 21 onto chromosome 14. A person who has had such a translocation in his or her gamete-producing cells is a carrier of familial Down syndrome. The carrier is normal because he or she still has two copies of all the essential genes on chromosome 21, despite the translocation. However, the same may not be true for the carrier's offspring.The diagram shows the six possible gametes that a carrier of familial Down syndrome could produce. Suppose that a carrier of familial Down syndrome mated with a person with a normal karyotype. Which gamete from the carrier parent could fuse with a gamete from the normal parent to produce a trisomy-21 zygote? Drag one of the gamete cells to the target of Group 1 in the diagram. Drag one of the zygote cells to the target of Group 2 in the diagram

First blank: 14-21-21 (Top left blue icon) Second Blank: 14-14-21-21-21 (Top right red icon)

How are human mitochondria inherited?

From the mother only

A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results

None of the females will have white eyes.

PART E: Which of these terms applies to an organism with extra sets of chromosomes?

Polyploid

PART D: What is the correct sequence of the three linked genes?

T-A-S

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?

The F2 generation would have included a higher percentage of pea plants producing round, yellow peas.

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of independent assortment?

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.

Which of the following is true of an X-linked gene, but not of a Y-linked gene?

The gene is present in both males and females

In humans, what determines the sex of offspring and why?

The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome.

Select the correct statement(s) about sex determination in animals

The mechanism of sex determination varies with different animal species.

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation?

The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

PART E: Of the following chromosomal abnormalities, which type is most likely to be viable in humans?

Trisomy

PART C: Which syndrome is characterized by the XO chromosome abnormality

Turner syndrome

During a single crossover event, how many strands of DNA must break? (Recall that DNA is double-stranded.)

four strands

What can we observe in order to visualize Mendel's Law of Segregation?

homologous chromosomes separating during meiosis I

Which of the following results in a situation in which the chromosome number is either 2n+1 or 2n-1?

aneuploidy

PART F: Mutant tetraploid plants ______.

are unable to interbreed with a diploid plant

PART A: What is the probability that a daughter of this mating will be a hemophiliac? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/24), or as a whole number.

0

PART A: Humans are diploid and have 46 chromosomes (or two sets). How many sets of chromosomes are found in each human gamete?

1

PART C: 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. Drag the correct label to the appropriate location in the table. Not all labels will be used.

1. 1/4 2. 1/2 3. 0 4. 1

PART B Suppose a diploid cell with three pairs of homologous chromosomes (2n = 6) enters meiosis. How many chromosomes will the resulting gametes have in each of the following cases? Drag one label into each space at the right of the table. Labels can be used once, more than once, or not at all.

1. 3 Only 2. 2 or 4 3. 0 or 6 4. 2,3 or 4 5. 0,3 or 6

PART B: 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+×XvYX+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.) Drag the correct label to the appropriate location in the table. Labels can be used once, more than once, or not at all.

1. All wild type 2. All wild type 3. All wild type 4. 1/2 wild, 1/2 vermilion

Chromosomal mutations are changes in the normal structure or number of chromosomes. Changes in chromosome structure can result from errors in meiosis or from exposure to radiation or other damaging agents. Certain changes in chromosome number can result from nondisjunction during either meiosis or mitosis. Both structural mutations and nondisjunction can play a role in trisomy 21, commonly known as Down syndrome. PART A: Changes in chromosome structure Part complete The diagram below shows two normal chromosomes in a cell. Letters represent major segments of the chromosomes. The following table illustrates some structural mutations that involve one or both of these chromosomes. Identify the type of mutation that has led to each result shown. Drag one label into the space to the right of each chromosome or pair of chromosomes. You can use a label once, more than once, or not at all.

1. deletion 2. Duplication 3. Translocation 4.Inversion 5. Duplication 6. Translocation 7. Inversion

At the time of Mendel's pea plant experiments, no one knew how organisms formed gametes. As Mendel studied the inheritance of two different characters, he wondered how the alleles for the two characters segregated into gametes. Mendel had two hypotheses for how this might work.Under the hypothesis of dependent assortment, the alleles inherited from the parental generation should always be transmitted to the next generation in the same combinations.Under the hypothesis of independent assortment, alleles for different characters should segregate independently of each other, meaning that alleles should be packaged into gametes in all possible combinations, as long as each gamete has one allele for each gene. The figure below shows the experiment that Mendel used to distinguish between these two hypotheses. The results of the experiment confirmed that the alleles for these characters undergo independent assortment. Drag the terms to the appropriate blanks to complete the sentences below. Not all terms will be used.

1. yyrr 2.YyRr 3.All possible creations 4.YR, Yr, yR,yr 5. Four, 9 to 3 to3 to 1

PART C: If the couple has four sons, what is the probability that all four will be born with hemophilia? Express your answer as a fraction (for example, 1/24), or as a whole number.

1/16

PART B: What is the probability that a son will be a hemophiliac? Express your answer as a fraction (for example, 1/24), or as a whole number.

1/2

A space probe discovers a planet inhabited by creatures that reproduce with the same hereditary patterns seen in humans. Three phenotypic characters are: height (T = tall, t = dwarf) head appendages (A = antennae, a = no antennae) nose morphology (S = upturned snout, s = downturned snout) Since the creatures are not "intelligent," Earth scientists are able to do some controlled breeding experiments using various heterozygotes in testcrosses. PART A: For tall heterozygotes with antennae, the offspring are: tall-antennae46dwarf-antennae7dwarf-no antennae42tall-no antennae5 Calculate the recombination frequency between T and A. Enter your answer as a percentage (for example, 10%).

12%

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-type778black-vestigial785black-normal158gray-vestigial162 Part A Part complete What is the recombination frequency between these genes for body color and wing size? Express your answer as a percentage.

17%

PART C: Scientists do a further testcross using a heterozygote for height and nose morphology. The offspring are: tall-upturned snout40dwarf-upturned snout9dwarf-downturned snout42tall-downturned snout9 Calculate the recombination frequency between T and S. Enter your answer as a percentage (for example, 10%).

18%

PART B: Humans are diploid and have 46 chromosomes. How many chromosomes are found in each human gamete?

23

PART D: 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.

4

Two genes of a flower, one controlling blue (B) versus white (b) petals and the other controlling round (R) versus oval (r) 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 F2 progeny are obtained.How many F2 plants of each of the four phenotypes do you expect?_____ blue-round : _____ white-oval: _____ blue-oval : _____ white-round Express your answer as four whole numbers separated by colons (for example, 400:300:200:100).

450 blue oval and white rounded, 50 each of blue round and white oval

PART B: For heterozygotes with antennae and an upturned snout, the offspring are: antennae-upturned snout47antennae-downturned snout2no antennae-downturned snout48no antennae-upturned snout3 Calculate the recombination frequency between A and S. Enter your answer as a percentage (for example, 10%).

5%

Assume that genes A and B are on the same chromosome and are 50 map units apart. An animal heterozygous at both loci is crossed with one that is homozygous recessive at both loci. Part A Part complete 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-type721 black-purple751 gray-purple49 black-red45 Part A Part complete What is the recombination frequency between these genes for body color and eye color? Express your answer as a percentage.

6%

PART G: 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 nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

PART F: 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 nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes for these two genes is possible in a gamete from this organism?

HT

In general, the frequency with which crossing over occurs between two linked genes depends on what?

How far apart they are on the chromosome

PART G: Most polyploid plants arise as a result of _____.

Hybridization

What name is given to the most common phenotype in a natural population?

Wild Type

A trait controlled by a gene located on either sex chromosome is called a sex-linked trait. In human genetics, however, this term has historically referred specifically to a trait controlled by a gene on the X chromosome (also called an X-linked trait).In this tutorial, you will explore the pattern of inheritance of sex-linked traits in humans and other animals. PART A - The inheritance of a skin condition in humans 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?

X- linked dominant

You design Drosophila crosses to provide recombination data for gene a, which is located on the chromosome shown in the figure below. Gene a has recombination frequencies of 14% with the vestigial-wing locus and 26% with the brown-eye locus. Part A Part complete Approximately where is a located along the chromosome?

about one-third of the distance from the vestigial-wing locus to the brown-eye locus

What phenomenon occurs when a particular allele will either be expressed or silenced, depending on whether it is inherited from a male or a female?

genomic imprinting