Biotest 11-13

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?

92 -Mitosis follows the duplication of the cell's DNA.

Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?

cleavage -In animal cells, the cleavage furrow forms when a ring of microfilaments contracts, causing the parent cell to be pinched in two.

Which of the following is found in binary fission but not in mitosis? Replicated strands of DNA separate. Following the process, a membrane separates the 2 copies. Replication of DNA begins at an origin. Duplicated chromosomes attach to the plasma membrane. The result produces 2 nuclei.

Duplicated chromosomes attach to the plasma membrane. -This is not true of mitosis.

Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?

G1 -In mammalian cells, this checkpoint is termed the restriction point.

Which of the following correctly matches a phase of the cell cycle with its description? M: duplication of DNA G2: cell division G1: follows cell division S: immediately precedes cell division All of the above are correctly matched

G1: follows cell division -After mitosis and cytokinesis, the newly formed daughter cells enter the G1 phase.

Which of the following is true of kinetochores? They interdigitate at the cell's equator and then move apart, causing the cell to elongate. They attach to the ring of actin along the cytoplasmic surface of the plasma membrane, causing the actin to contract to form the cleavage furrow. They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers. They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. They are sites at which microtubules attach to chromosomes.

They are sites at which microtubules attach to chromosomes. -As the spindle depolymerizes, the kinetochores appear to move along the spindle fiber, dragging the attached chromosomes with them.

Why is it difficult to observe individual chromosomes with a light microscope during interphase?

They have uncoiled to form long, thin strands. -Except during the M phase, the DNA is extended, allowing its genes to be transcribed for protein synthesis.

Which of the following is true of benign tumors, but not malignant tumors? They migrate from the initial site of transformation to other organs or tissues. They can divide indefinitely if an adequate supply of nutrients is available. They are the result of the transformation of normal cells. They remain confined to their original site They have an unusual number of chromosomes.

They remain confined to their original site -Benign tumors can often be surgically removed because their boundaries are well defined, whereas some malignant tumors go on to metastasize.

In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?

large cells containing many nuclei