Module 5

A cell is dividing by binary fission. What can you conclude?

The cell is prokaryotic.

Which of the following are surrounded by fibrils that make up the pericentriolar material?

Centrioles

What evolutionary advantage is provided by sexual reproduction?

Increased genetic diversity

What is the function of kinetochores?

Kinetochores attach to microtubules during mitosis.

____ contain identical DNA sequences and are held together by ____ during mitosis.

Sister chromatids; cohesin proteins

Homologous pairs of chromosomes separate during meiosis I.

True

Cytokinesis in animal cells involves contraction of a ring of ____ microfilaments.

actin plus myosin

Cytokinesis in plant cells occurs via the formation of a(n)

cell plate.

Eukaryotic chromosomes are composed of

chromatin

A bacterial chromosome consists of a

circular DNA molecule many times larger than the cell.

A cell in the G2 phase

has twice the amount of DNA present in a telophase nucleus.

Eukaryotic chromosomes consist of

linear DNA molecules complexed with positively charged histone proteins.

The process occurring at arrow 3 in the accompanying figure is

meiosis

Gametophyte plants produce gametes using

mitosis

The M phase of the cell cycle involves two main processes:

mitosis and cytokinesis.

In fungi and protists, gametes produced by ____ of haploid cells fuse to form a ____ zygote, which then undergoes ____ to restore the haploid chromosome number.

mitosis, diploid, meiosis

The ____ is responsible for the separation of the chromosomes during the ____ of mitosis.

mitotic spindle; anaphase

Cytokinesis generally begins.

telophase

An animal with a diploid number of 36 chromosomes will have ____ chromosomes in its gametes and ____ chromosomes in its somatic cells.

18; 36

In a human cell at prophase I, there are ____ tetrads.

23

In the accompanying figure, which combination of letters accurately represents two sister chromatids?

A and C

During which stage of meiosis do the sister chromatids separate?

Anaphase II

Sister chromatids separate and chromosomes move to opposite poles.

Anaphase II

Which event occurs in prophase II?

Condensation of the chromatin into chromosomes

Nuclear envelope forms around single-stranded chromosomes.

Telophase II

What would happen if meiosis did not occur in sexually reproducing organisms?

The chromosome number would double in each generation.

When is a cell in metaphase?

The chromosomes are aligned at the midplane of the cell.

The nuclear envelope fragments during the prometaphase stage.

True

To prevent disastrous consequences, the eukaryotic cell cycle is controlled by

a series of cell cycle checkpoints.

During prophase I, each chiasma represents

a site of crossing-over.

Sister chromatids separate at their centromeres.

anaphase

Plant hormones known as ____ stimulate mitosis.

cytokinins

Nucleosomes are best described as

eukaryotic DNA associated with histone proteins.

The cell cycle of a typical somatic cell consists of the ____ and M phases.

interphase

Chromosomes align at the cell's midplane.

metaphase

At the completion of oogenesis, ____ are produced.

one egg cell and three polar bodies

Homologous chromosomes undergo synapsis during

prophase I

In unwound chromatin, nucleosomes are organized into large coiled loops held together by

scaffolding proteins.

Chromosomes decondense.

telophase

During prophase I of meiosis, homologous chromosomes lie side by side. This phenomenon is known as

tetrad formation.

In the accompanying figure, which combination of letters accurately represents two homologous chromosomes?

A and D

Homologous chromosomes separate and move to opposite poles.

Anaphase I

Which of the following is produced by meiosis?

Animal gametes

Microtubules of the mitotic spindle attach directly to each chromosome at the centromere.

False

Once nerve cells become mature, they do not typically undergo cell division. Based on your knowledge of the cell cycle, you might predict that mature nerve cells become arrested in the ____ of the cell cycle.

G0 phase

____ ______________organized on chromosomes carry the information that controls the functions of the cell.

Genes

Tetrads line up at the cell equator.

Metaphase I

Spindle microtubules attach to kinetochores.

Prometaphase

Crossing-over occurs.

Prophase I

Homologous chromosomes undergo synapsis.

Prophase I

Which phase of cell division is depicted in the accompanying figure?

Prophase I of meiosis

Chromosomes are duplicated during the ____ of the cell cycle.

S phase

Cell-cycle checkpoints temporarily block key events from being initiated during the cell cycle.

True

Enzymes required for DNA replication are synthesized during the G1 phase.

True

Duplicated centrioles move to opposite poles of a dividing ____ cell during the ____ of the cell cycle.

animal; prophase

During prophase, ____ is(are) compacted into visible chromosomes.

chromatin

To control the cell cycle,

cyclins fluctuate during the cell cycle.

The mitotic spindle is made of

microtubules

The function of nucleosomes is to

prevent DNA strands from tangling.

Nuclear envelope fragments.

prometaphase

Chromatin condenses.

prophase

Homologous chromosomes can be identified and/or characterized by

their similar and characteristic staining patterns.

A nucleosome consists of DNA wrapped around scaffolding proteins.

False

A pair of centrioles is found at the center of the microtubule-organizing center in plant cells.

False

An animal zygote is a haploid cell.

False

Bacteria divide asexually by mitosis.

False

For each animal cell that begins oogenesis, the number of ova produced is four.

False

In animal cells, cytokinesis occurs via the formation of a cell plate.

False

In the cell cycle, DNA is replicated during the G2 phase.

False

Mitotic spindle forms.

prophase

What is not a hallmark of prophase?

Spindle fibers pull chromosomes to opposite sides of the cell.