Mastering Biology Chapter 12

Which of the following is true?

The chance of having a child with a chromosomal abnormality increases with the age of the mother.

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.

Which syndrome is characterized by the XO chromosome abnormality?

Turner syndrome

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

wild type

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

One map unit is equivalent to which of the following values?

1% frequency of recombination between two genes

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

The diagram below shows two normal chromosomes in a cell. Letters represent major segments of the chromosomes. The diagram shows two chromosomes. The first chromosome, green, consists of two arms. The left arm, short, consists of segments A and B. The right arm, long, consists of a sequence of C, D, E, F, G, and H segments. The second chromosome (yellow) consists of two arms. The left arm, short, consists of a segment I. The right arm, long, consists of a sequence of J, K, L, M, and N segments. 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

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

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

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 white cells (representing gametes) to the white target in the diagram. Drag one of the pink cells (representing zygotes) to the pink target.

14 (green) 21 (yellow) 21 (yellow) 14 (green) 21 (yellow) 14 (green) 14 (green) 21 (yellow) 21 (yellow) 21 (yellow)

Which of the following is true regarding this new fetal DNA test?

A decreased number of false positive tests for both Down syndrome and Trisomy 18.

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.

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.

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

A triploid cell

When can nondisjunction occur? Choose the best answer. -In meiosis, when sister chromatids fail to separate -In mitosis, when sister chromatids fail to separate -In meiosis, when homologous chromosomes fail to separate

All three answers are correct.

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

How is the fetal DNA used in this new screening tool unique?

It is not from a cell, but is floating freely in the mother's blood.

Which of the following best summarizes current research on this new fetal DNA test?

It works well for finding errors in chromosome number.

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

Trisomy

Your 28 year old friend is pregnant. Which of the following screenings is she most likely to initially have to test for Down syndrome?

blood test

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

how far apart they are on the chromosome

Video Tutor Session Quiz: Sex-Linked Pedigrees

part a: X^H Y^0 part b: it could be X^B X^B or X^B X^b part c: 100% part d: X^B X^b part e: it could be X^B X^B or X^B X^b