Chapter 13 Prelecture

A species has ten distinct types of chromosomes. A haploid cell of this species contains how many chromosomes? 5 It is impossible to determine based on the information given. 20 10

10 Haploid cells only contain one copy of each chromosome.

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes. 32 8 64 30 16

16 16 is half of 32.

Normal human gametes carry _____ chromosomes. 46 5 23 23 pairs of 46 pairs of

23 This is the number of chromosomes in a single set of human chromosomes.

Which statement is correct concerning the relationship between chromosomes and chromatids? A replicated chromosome contains a single chromatid. An unreplicated chromosome contains two sister chromatids. An unreplicated chromosome contains a single chromatid. A replicated chromosome contains two sister chromatids.

A replicated chromosome contains two sister chromatids. A replicated chromosome contains two identical DNA double helices that correspond to each sister chromatid.

asexual reproduction

A single individual is reproducing.

telophase I and cytokinesis

At the end of telophase I and cytokinesis there are two haploid cells.

Which of the following is true? Down syndrome is caused by an extra copy of chromosome 21. Mistakes in meiosis are not usually a problem. Gametes with an abnormal chromosome complement are said to be haploid. Mistakes in meiosis in humans are rare.

Down syndrome is caused by an extra copy of chromosome 21. Down syndrome is characterized by trisomy 21

anaphase I

During anaphase I homologous chromosomes, consisting of sister chromatids, migrate to opposite poles

anaphase II

During anaphase II sister chromatids separate and migrate to opposite poles.

interphase

During interphase the centrosome duplicates and the chromosomes are not condensed.

metaphase I

During metaphase I tetrads align along the metaphase plate.

telophase II and cytokinesis

Four haploid cells are present at the end of telophase II and cytokinesis.

Which statement is FALSE concerning gametes produced by meiosis? Gametes contain half as many chromosomes as the parent cell. Gametes contain nonrandom combinations of maternal and paternal chromosomes. Gametes contain a random assortment of maternal and paternal chromosomes. Gametes contain a random assortment of maternal and paternal alleles.

Gametes contain nonrandom combinations of maternal and paternal chromosomes. This statement is false. Gametes receive a random assortment of maternal and paternal chromosomes when homologs separate in meiosis I.

How would genetic variation be affected if, during meiosis I, maternal chromosomes always lined up together on one side of the metaphase plate and paternal chromosomes always lined up on the other side (ignoring the effects of crossing over)? Gametes would contain either maternal chromosomes only or paternal chromosomes only. Gametes would contain paternal chromosomes only. Gametes would contain maternal chromosomes only. Gametes would contain different combinations of maternal and paternal chromosomes

Gametes would contain either maternal chromosomes only or paternal chromosomes only. All maternal chromosomes would go to one daughter cell and all paternal chromosomes to the other, so different combinations would not be produced in gametes.

prophase I

Homologous chromosomes pair during prophase I.

metaphase II

Metaphase II is essentially the same as mitotic metaphase except that the cells are haploid.

Which of the following is a difference between mitosis and meiosis? Sister chromatids only separate during meiosis. Genetic variation is only produced during mitosis. Chromosomes only replicate prior to the start of mitosis. Only in meiosis do homologous chromosomes pair up.

Only in meiosis do homologous chromosomes pair up. In prophase I of meiosis homologs pair, and then separate to form haploid daughter cells.

prophase II

The events of prophase II are essentially the same as those of mitotic prophase except that prophase II cells are haploid.

Homologous chromosomes migrate to opposite poles during _____. metaphase I telophase II and cytokinesis prophase II metaphase II anaphase I

anaphase I During anaphase I sister chromatids remain attached at their centromeres, and homologous chromosomes move to opposite poles.

During _____ sister chromatids separate. metaphase I prophase I anaphase II interphase prophase II

anaphase II Anaphase II is essentially the same as mitotic anaphase except that the cell is haploid.

Which of the following creates new combinations of alleles along one chromosome? mitosis independent assortment crossing over nondisjunction

crossing over During crossing over recombination occurs, leading to new combinations of alleles on a chromosome.

Meiosis II typically produces _____ cells, each of which is _____. Meiosis II typically produces _____ cells, each of which is _____. four ... identical to the other two ... haploid four ... diploid four ... haploid two... diploid

four ... haploid At the end of meiosis II there are typically 4 haploid cells.

Human gametes are produced by _____. asexual reproduction meiosis fertilization mitosis the cell cycle

meiosis Meiosis produces haploid gametes from a diploid parental cell.

During _____ chromosomes align single file along the equator of a haploid cell. metaphase II prophase I anaphase I metaphase I telophase I and cytokinesis

metaphase II Metaphase II is essentially the same as mitotic metaphase except that the cell is haploid.

Synapsis occurs during _____. anaphase II telophase I and cytogenesis prophase I metaphase II prophase II

prophase I Synapsis, the pairing of homologous chromosomes, occurs during prophase I.

During _____ a spindle forms in a haploid cell. metaphase II telophase I and cytokinesis anaphase II prophase I prophase II

prophase II Prophase II is essentially the same as mitotic prophase except that the cells are haploid.

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids. telophase I telophase telophase II metaphase II interphase

telophase I At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of two sister chromatids each.

At the end of _____ and cytokinesis there are four haploid cells. prophase I prophase II interphase anaphase I telophase II

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

Meiosis I produces _____ cells, each of which is _____. two... identical to the other two ... haploid four ... haploid four ... diploid two... diploid

two ... haploid At the end of meiosis I there are two haploid cells.