Mastering biology chapter 13

How many double-helical DNA molecules will be present in the sperm and egg cells of dogs that are diploid animals that contain 78 replicated chromosomes in each cell that enters meiosis?

39

For the duration of meiosis I, each chromosome _____.

Consists of two sister chromatids joined by a centromere

Which of the following happens at the conclusion of meiosis I?

Homologous chromosomes of a pair are separated from each other.

Crossing over normally takes place during which of the following processes?

Meiosis I

Homologous pairs of chromosomes align opposite to each other at the equator of a cell during ________.

Metaphase I of meiosis

Which of the following occurs in meiosis but not in mitosis?

Synapsis of chromosomes

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

After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.

Haploid, and the chromosomes are each composed of two chromatids

Independent assortment of chromosomes occurs during _____.

Meiosis I only

Which of the following statements about meiosis and mitosis is true?

Meiosis II is similar to mitosis in that sister chromatids of each chromosome separate.

What is the ploidy of this cell model?

2n = 6

What proportion of chromosomes in a man's skin cell are maternal chromosomes?

1/2

If a cell has 24 chromosomes, how many chromosomes would each of its four daughter cells have after meiosis?

12

Homologous chromosomes migrate to opposite poles during _____.

Anaphase I

In meiosis, homologous chromosomes are separated during ________.

Anaphase I

What phase of meiosis is seen in the accompanying figure?

Anaphase I

Centromeres split and sister chromatids migrate to opposite poles in ________ of meiosis.

Anaphase II

During _____ sister chromatids separate.

Anaphase II

The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid. 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.

An advantage of asexual reproduction is that it _____.

Enables the species to rapidly colonize habitats that are favorable to that species

What is the ploidy of organisms that have two sets of chromosomes?

2n

Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?

38

What is the ploidy of this cell model?

Haploid (one set)

Which of the following statements about the meiosis are correct? Select all that apply.

-A chiasma forms between two of the four molecules of double-stranded DNADNA on duplicated homologous chromosomes. -Non-sister chromatids are found on two different homologs.

Which processes lead to most genetic variation in sexually reproducing organisms? Select all that apply.

-Random fertilization -Independent assortment of chromosomes in meiosis -Crossing over

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?

2

The chromosome number of hexaploid wheat, Triticum aestivum, can be represented as _____.

6n

The egg of a fruit fly has 4 individual chromosomes. How many chromosomes are in a somatic (body) cell of a fruit fly?

8

Which of the following stages of meiosis is correctly matched to chromosome composition at that stage?

Anaphase I−−two sister chromatids

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?

At the end of meiosis I

Which of these gametes contains one or more recombinant chromosomes?

B and C

Sexual reproduction _____.

Can produce diverse phenotypes that may enhance survival of a population in a changing environment

Homologous chromosomes _____.

Carry information for the same traits

Which structure is directly correlated with the production of genetic variability in the daughter cells produced during meiosis?

Chiasma

What are homologous chromosomes?

Chromosomes that are similar in their size, shape, and gene content

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____.

Half the number of chromosomes and one-fourth the amount of DNA.

True or false? A haploid organism has one pair of homologous chromosomes.

False

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

Four ... Haploid

The somatic cells of a privet shrub each contain 46 chromosomes. How do privet chromosomes differ from the chromosomes of humans, who also have 46?

Genes of privet chromosomes are significantly different from those in humans.

What makes sexually reproduced offspring genetically different from their parents?

Genetic recombination during meiosis

Which statement about the difference between homologous chromosomes and sister chromatids is correct?

Homologous chromosomes contain the same genes but often different alleles. Sister chromatids contain the same genes and the same alleles.

A key difference between mitosis and meiosis is

Homologs pair up and crossing over happens during meiosis I but does not happen in mitosis

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

Length, centromere position, staining pattern, and traits coded for by their genes

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

Metaphase II

Sister chromatids separate from each other during _____.

Mitosis and meiosis II

When does DNA replication take place regarding meiosis? DNA replication _____.

Occurs before meiosis I begins

What is the composition of a tetrad at the beginning of prophase I?

One pair of homologous chromosomes

Synapsis occurs during _____.

Prophase I

When we first see chiasmata under a microscope, we know that _____.

Prophase I is occurring

During _____ a spindle forms in a haploid cell.

Prophase II

What is a major difference between mitosis and meiosis I in a diploid organism?

Sister chromatids separate in mitosis; homologous pairs of chromosomes separate in meiosis I.

Review the checklist of tips for drawing chromosomes during independent assortment. Four of the tips were followed, but one was not. Which one?

Start with replicated chromosomes.

What information can not be obtained from an individual's karyotype?

The sequence of bases of a particular gene

Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis.

There would be less genetic variation among gametes.

What is the ploidy of this cell model?

Triploid

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

Two...Haploid

What is the ploidy of this cell model?

n = 6