BIOL Ch. 10&11

As the hamster cell replicates, what structures condense and line up on the cell's equator?

Chromosomes

Meiosis II separates sister chromatids. What might make sister chromatids differ from each other?

If sister chromatids were recombined during crossing over

Synapsis is the side-by-side alignment of

homologous chromosomes

A tetrad is made up of

two homologous chromosomes, each consisting of two chromatids

Random orientation of chromosomes during meiosis increases the amount of variation in the next generation. What other process during meiosis leads to an increase in variation in the next generation?

Crossing over between homologous chromosomes

The diagram below represents a cell from a jack jumper ant. The cell is about to undergo mitosis and the DNA has been replicated. The jack jumper ant __________.

is 2n = 2; has one pair of homologous chromosomes

A cell biologist examines a diploid cell from a barley plant during prometaphase of mitosis and determines that 28 chromatids are present. The role of meiosis in this plant is to __________. (Check all that apply.)

-Produce 4 daughter cells that are genetically identical to each other -Reduce the number of chromosomes per cell from 28 to 14.

Consider a cell that has four pairs of chromosomes. What is the number of possible chromosome orientations in that cell?

16

Which of the following describes meiosis II in humans?

1N -> 1N

Nondisjunction is the failure of homologous chromosomes to separate during meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. As a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. This produces daughter cells with an imbalance of chromosomes. If 22 pairs of homologous chromosomes segregate normally during meiosis I in humans (n = 23) but we have nondisjunction of 1 pair, then at the end of meiosis II we will have

2 cells with 24 chromosomes and 2 cells with 22.

If a homologous pair of chromosomes fails to separate during meiosis I, what will be the result?

2 gametes will have 2 of the affected chromosomes, and 2 gametes will have 0 of the affected chromosomes.

If crossing over occurs between two chromatids on a single pair of homologous chromosomes, how many gametes will have a recombinant phenotype?

2 of the 4

How many generations does it take for a single bacterial cell to become 256?

8

Which of the following statements about crossing over is true?

All of these are false statements.

The sister chromatids of a chromosome fully separate during ________ of mitosis.

Anaphase

Match each event with the appropriate stage of meiosis.

Anaphase I: -Chiasmata breakMembers of each homologous pair go to opposite poles of the cell. -Sister chromatids remain attached. -Each homologue moves to one pole, taking both -sister chromatids with it. -Chromosomes remain duplicated. Anaphase II: -Centromeres split. -Sister chromatids separate and are pulled to opposite poles of the cell. -Chromosomes change from duplicated state to unduplicated state. Neither: -Chromosomes begin to condense. -Crossing over occurs. -Spindle begins to form. -Nuclear membrane re-forms. -DNA replication occurs. Both: -Kinetochore microtubules shorten.

Which statement about mitosis and cytokinesis is TRUE?

At the end of cytokinesis there are two daughter cells with a normal complement of diploid genetic material.

Complete the sentences on the cell cycle with the correct terms.

G1 is the longest phase of the cell cycle for most cells. During synthesis the cell replicates its genome. G2 is a growth phase for the cell that happens after DNA synthesis has occurred. The process by which cellular chromosomes are divided and separated from each other is called mitosis. It is during cytokinesis that the cytoplasm divides. The resting phase of the cell cycle is called G0.

Random orientation of homologous chromosomes occurs in ________ of meiosis.

Metaphase I

Match each description with the appropriate type of cell division.

Mitosis : -Homologous chromosomes behave independently of each other. -The new cells produced are genetically identical to each other and to the original cell. -During the first nuclear division, sister chromatids separate and move to opposite poles. -DNA replication is followed by a single nuclear division. Meiosis: -There are 2 nuclear divisions with no DNA replication between them. -During the first nuclear division,homologous chromosomes separate and move to opposite poles. -Independent assortment of maternal and paternal chromosomes. -Crossing over occurs. -Synapsis occurs. -During the first nuclear division, sister kinetochores fuse and are attached to the same pole. -The chromosome number is reduced from 2 sets to 1 set. -During the first nuclear division, chromosomes line up along the equatorial plate in pairs. Neither mitosis nor meiosis: -Nuclear division occurs twice but cytokinesis occurs only once. Both mitosis and meiosis : -Chromosomes condense before they attach to the spindle.

Which of the following represents the correct order of the phases of mitosis?

Prophase → metaphase → anaphase → telophase

Which of the following is unique to meiosis?

crossing over

The division of the cytoplasm is called __________.

cytokinesis

In animals, cells that will eventually undergo meiosis to produce the gametes are set aside early in the course of development. These cells are called __________.

germ-line cells

The body cells of hamsters have 44 chromosomes. After mitosis and cell division, how many chromosomes should each hamster cell have?

44

Using the chart at the beginning of the animation and your knowledge of cells, what stage of the cell cycle do most cells spend the majority of their lives?

G1

Place the characteristic with the correct corresponding structure.

Homologous chromosomes: -These are the maternal and paternal pairs seen in the individual. They are inherited. -A karyotype consists of the chromosomes present in an individual. Chromatids are not counted. -23 pairs of chromosomes are seen in humans. Sister chromatids: -The sister chromatids are formed during the mitotic stage of interphase. -They are the replica of a chromosome where one chromosome has two chromatids. -The sister chromatids are separated during mitosis and are sent to separate cells. -The sister chromatids are attached by cohesin.

Which of the following statements about the mitotic spindle is TRUE?

Kinetochore microtubules in the mitotic spindle attempt to connect to kinetochore proteins in the centromeres of the condensed chromosomes.

Daughter cells produced in meiosis have

half the number of chromosomes as daughter cells produced in mitosis

The structure that divides the bacterial cell in two is termed the __________.

Cross septum

The success of DNA replication is assessed during the ______ phase.

G2

Crossing over is possible due to what event that occurs in meiosis I but not mitosis?

Synapsis

Arrange the following events in the proper order in which they occur during meiosis I. a. Separation of homologous chromosomes b. Synapsis c. Crossing-over d. Independent assortment

b, c, d, a

Which of the following events do not occur in prophase of mitosis?

Chromosomes are replicated

What happens immediately after the chromosomes line up on the cell's equator?

Chromosomes separate and move to opposite ends of the cell.

In a human somatic cell (normal body cell) that is in G2, what would be true about chromosome number and structure? Check all that apply.

-These cells would be considered diploid (2n). -These cells would contain homologous chromosomes. -These cells would contain sister chromatids.

A cell biologist examines a diploid cell from a kangaroo during prometaphase of mitosis and determines that 32 chromatids are present. The role of fertilization in this animal is to __________. (Check all that apply.)

-increase the number of chromosomes per cell from 8 to 16 -combine the chromosomes of 2 haploid cells into a single diploid cell

Complete the sentences on the control of the cell cycle with the correct terms.

After S phase sister chromatids appear to share a common centromere. During G1, cells undergo the major portion of their growth. During interphase, all eukaryotic cells synthesize large amounts of tubulin. During G2, chromosomes begin to undergo condensation. The kinetochore is a disk-like protein structure found at the point of constriction on the chromosome.

The generation time for the five bacterial species mentioned in the animation are shown below. Which of these bacteria would be the best organism for scientists to use to study genetics, and why?

Escherichia coli because many generations can be examined in a short period of time.

Which of the following represents the correct order of the phases of the cell cycle?

G1 → S → G2 → M

The cell cycle is regulated by checkpoints during the _______ phases.

G1, G2, and M

DNA repair enzymes will be highly active during which phase of the cell cycle?

G2

Fill in the blanks with the words provided.

In life cycles that alternate between haploid and diploid stages, meiosis acts to reduce the number of chromosomes per cell from two sets to one set. In life cycles that alternate between haploid and diploid stages, fertilization acts to double the number of chromosome per cell from one set to two sets. In life cycles that alternate between haploid and diploid stages, mitosis acts to keep the number of chromosomes per cell the same. In animals, a single diploid cell called a zygote divides by mitosis to give rise to all the cells of the adult body. During fertilization, each haploid gamete contains the entire genetic contribution from one of the two parents. Cells that have one set of chromosomes are called haploid. Cells that have two sets of chromosomes are called diploid.

Separation of ________ occurs in anaphase II of meiosis.

Sister chromatids

Why do chromosomes condense during prophase?

So that they will not be damaged when they are moved around the cell.

Identify the stages of meiosis by filling in the blanks and then rearrange the sentences to place the stages in the correct order starting with prophase I.

Synapsis of homologous chromosomes and crossing over take place during prophase I. Chromosomes line up in pairs along the metaphase plate during metaphase I. The 2 members of each homologous pair are pulled to opposite poles of the cell while sister chromatids remain attached during anaphase I. Nuclear envelopes reform around 2 separate haploid nuclei during telophase I. A new spindle apparatus begins to form in 2 separate haploid cells during prophase II. Unpaired chromosomes line up along the metaphase plate during metaphase II. Sister chromatids separate and are pulled to opposite poles of the cell during anaphase II. Nuclear envelopes reform around 4 separate haploid nuclei during telophase II.

Which of the following features are unique to meiosis?

Synapsis, homologous recombination, and reduction division

Complete the sentences on the control of the cell cycle with the correct terms.

The G1/S checkpoint is the primary point of the cell cycle that is influenced by external signals. The spindle checkpoint ensures that all of the chromosomes are attached to microtubules. The G2/M checkpoint assesses whether DNA is damaged, and also whether DNA replication has completed. Passage through checkpoints is controlled by Cdk enzymes.

A cell has a mutation that prevents cytokinesis from occurring. What is the most likely consequence of this mutation?

The nuclear material will divide but the cell will not, resulting in a cell with multiple nuclei.

In streptococci, why is new cell wall only produced in certain regions of the daughter cells?

These bacteria possess cell wall from the parent, and only need to produce a new cell wall in certain regions.

Which of the following statements about microtubules during anaphase are TRUE?

Those attached to chromosomes shorten, while those that are unattached elongate.

In germline cells, when does DNA replicate?

during S phase

At the end of meiosis II, there are

four haploid cells, with each chromosome consisting of a single chromatid.