BIO 150 Meisosis

Sexual reproduction results in an increase in genetic diversity because:

- during prophase I, genes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes. - during fertilization, the gametes that fuse are random so that a large number of chromosomal combinations are possible in the new organism. - during metaphase I, the bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes.

Sexual reproduction results:

- in a new generation that is not genetically identical to its parents - from combining genetic material from two gametes. - in a new generation with the same number of chromosomes as each parent. - in offspring that are not genetically identical.

The epithelial cells in the skin of an animal have 24 chromosomes. How many chromosomes are present in the gametes of this animal?

12

Cell cycle checkpoints: - provide opportunities to check if the cell has carried out steps necessary for cell division. - All of these choices are correct. - act as a brake on cell division if something is not right. - can involve the protein p53.

All of these choices are correct.

Cell division is regulated by: - signals that indicate that the cell has reached a sufficient size. - All of these choices are correct. - signals about the nutritional status of the cell. - signals that indicate that DNA has been replicated. - growth factor signals.

All of these choices are correct.

How would the loss of p53 activity affect a cell? - All of these choices are correct. - The G1/S checkpoint would not be functional. - CDK activity would not be appropriately regulated. - DNA damage could accumulate.

All of these choices are correct.

Which of the following statements regarding the cell cycle is TRUE? - It is regulated by cyclins and CDKs. - It has many major cell cycle checkpoints. - All of these choices are correct. - It can be "paused" by the action of p53. - Different levels of cyclins are observed at different cell cycle stages.

All of these choices are correct.

Which of these events does NOT include a checkpoint in the cell cycle? - the transition from G1 to S phase - All of these events include a checkpoint in the cell cycle. - the transition from G2 to M phase - the beginning of M phase

All of these events include a checkpoint in the cell cycle.

Which of the following is NOT a characteristic of meiotic cell division: - Cell division requires two rounds of nuclear division. - Daughter cells are genetically identical. - Cell division results in the formation of four daughter cells. - Cell division results in the production of gametes.

Daughter cells are genetically identical.

During meiosis, two rounds of DNA synthesis are required to form four gametes from one parent cell.

False

Which major checkpoint delays the cell cycle when DNA replication is incomplete?

G2 checkpoint

What would happen if crossing over occurred between sister chromatids?

Nothing would happen because sister chromatids are genetically identical or nearly identical.

A researcher is evaluating the expression of p53 in cells she is culturing in the laboratory. She notices that in a small group of cells, high levels of phosphorylated p53 occur in the nuclei. What can she deduce about these cells?

These cells likely contain damaged DNA.

Which of the following is NOT true about gametes?

They are genetically identical to other gametes formed during meiosis.

How do new cyclin proteins appear in the cytoplasm?

They are made through protein synthesis.

Most of the significant changes in activities and functions that accompany passage through a cell cycle checkpoint are regulated by the:

activation of kinase enzymes.

When do sister chromatids separate in meiosis?

anaphase II

Another name for non-sister chromatids is:

homologous chromosomes

In meiosis, recombination occurs:

only during prophase I and involves exchange between chromatids of homologous chromosomes.

Many of the specific functions that are triggered when a cell passes one of the cell cycle checkpoints result from activation of enzymes and other proteins. A common mechanism for this activation is:

phosphorylation of specific proteins.

During meiosis II:

sister chromatids are separated

Synapsis is best described as the:

the pairing of homologous chromosomes in prophase I

A cell in prophase I of meiosis has _____ as many chromosomes as each of the daughter cells following cytokinesis of meiosis II.

twice