Mastering Biology 10

During _____ sister chromatids separate.

anaphase II

The cells below show the eight possible combinations of chromosomes that the daughter cells of meiosis II can receive. Sort each daughter cell into the appropriate bin depending on which arrangement at metaphase I would create it.

arrangement 1: 8 and 3 arrangement 2: 5 and 1 arrangement 3: 6 and 2 arrangement 4: 4 and 7

Meiosis II typically produces _____ cells, each of which is _____.

four haploid

If you look through a microscope and see a cell with chromosomes lined up two by two, what stage of cellular reproduction must you be looking at?

meiosis I only

Crossing over, resulting in an increase in genetic variation, occurs between _____.

nonsister chromatids of homologous chromosomes

Meiosis I produces _____ cells, each of which is _____.

two ... haploid

First, drag blue labels onto blue targets only to identify each stage of the life cycle. Next, drag pink labels onto pink targets only to identify the process by which each stage occurs. Then, drag white labels onto white targets only to identify the ploidy level at each stage.

A. 2n B. 2n C. meiosis D. meiosis E. n F. egg G. sperm H. n I. fertilization J. 2n K. zygote L. mitosis M. 2n N. meiosis O. n P. egg

Drag the labels from the left to their correct locations in the concept map on the right.

A. Chromatin B. Genes C. Chromosomes D. Genome E. Traits F. Locus G. Gametes

Homologous chromosomes migrate to opposite poles during ___

Anaphase I

Which of these gametes contains one or more recombinant chromosomes?

B and C

Draw the diagrams of the stages of meiosis onto the targets so that the four stages of meiosis I and the four stages of meiosis II are in the proper sequence from left to right.

Meiosis involves two sequential cellular divisions. In meiosis I, homologous chromosomes pair and then separate. Thus, although the parent cell is diploid (containing two chromosome sets, one maternal and one paternal), each of the two daughter cells is haploid (containing only a single chromosome set). In meiosis II, the sister chromatids separate. The four daughter cells that result are haploid.

Homologous pairs of chromosomes are lined up independently of other such pairs during _____.

Metaphase I

During _____ chromosomes align single file along the equator of a haploid cell.

Metaphase II

Drag the labels to their appropriate targets to correctly identify the various chromosome structures. Labels can be used more than once.

a) non-homologous chromosomes b) sister chromatids c) homologous chromosomes d) centromere e) non-sister chromatids f) homologous chromosomes g)sister chromatids

Imagine you found a hypothetical organism. You examine one of its gametes and you see that it contains 5 chromosomes. How many chromosomes will one of its body cells contain just before mitosis begins?

10

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16. 16 is half of 32.

In human gamete production there is an average of _____ crossover events per chromosome pair.

2-3 These crossover events increase the genetic variation among gametes.

How many chromosomes do normal human gametes carry

23

Which of these gametes contain one or more recombinant chromosomes?

B, C, F, G

Which of these cells is (are) haploid?

C and D Once meiosis I is completed, cells are haploid.

What is the point of attachment between two sister chromatids of a duplicated chromosome called?

Centromere

Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

Crossing over prevents homologous chromosomes from separating during meiosis I.

False

How are human gametes produced

Meiosis

Synapsis occurs during _____.

Prophase I

During _____ a spindle forms in a haploid cell.

Prophase II

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

Telophase I

At the end of _____ and cytokinesis there are four haploid cells.

Telophase II

Mitosis goes on continuously in most parts of the body, whereas meiosis takes place only in ___.

The Gonads

If crossing over did not occur, which of the following statements about meiosis would be true? Select all that apply.

There would be less genetic variation among gametes.

The following processes are associated with meiosis and the sexual life cycle: DNA replication before meiosis crossing over chromosome alignment in metaphase I and separation in anaphase I chromosome alignment in metaphase II and separation in anaphase II fertilization. Sort each process into "hereditary only", "genetic variation only", or "both".

They are all both

As a result of crossing over, sister chromatids are no longer identical to each other.

True

Crossing over occurs at the ends of chromosomes, rather than near the centromeres.

True

For crossing over to occur, homologous chromosomes must align precisely early in prophase I so that nonsister chromatids can exchange corresponding segments of DNA.

True

Which processes lead to most genetic variation in sexually reproducing organisms?

crossing over, random fertilization, independent assortment of chromosomes in meiosis