) When animal cells are grown in a petri dish, they typically stop dividing once they have formed a single,
unbroken layer on the bottom of the dish. This arrest of division is an example of
A) density-dependent inhibition.
B) cell division repression.
C) growth factor desensitization.
E) cell constraint.
Tissue-cultured skin cells will stop dividing when which of the following occurs?
A) The cells run out of growth factors due to the crowding of neighboring cells.
B) The toxic waste products from other cells in the culture cause significant changes in the pH.
C) The cells reach the end of their reproductive life.
D) Neighboring cells release cell division repressor factors.
E) A clearing occurs that inhibits all cells in the culture.
You are asked to culture an unidentified sample of animal tissue. You notice that the cells seem not to exhibit density-dependent inhibition. Which of the following choices would be the most likely source for this tissue sample?
A) the sperm-producing tissue of the testis
B) a cancer
C) the skin
D) the fetal liver
E) a scar
If the S phase was eliminated from the cell cycle, the daughter cells would
A) be genetically identical.
B) have half the genetic material found in the parental cell.
C) synthesize the missing genetic material on their own.
D) be genetically identical to the parental cell.
E) None of the choices are correct.
Which of the following is a difference between mitosis and meiosis?
A) In meiosis four daughter cells are produced, whereas in mitosis two daughter cells are produced.
B) All of the choices are correct.
C) In mitosis cytokinesis occurs once, whereas in meiosis cytokinesis occurs twice.
D) Cells produced by mitosis are diploid; cells produced by meiosis are haploid.
Which of the following is a consequence of a reproduction system that is based on the union of haploid gametes?
A) the prevention of sexual reproduction
B) offspring that have enhanced genetic diversity and a diploid chromosome complement that is the same size as their parents'
C) offspring that have enhanced genetic diversity and a diploid chromosome complement that is twice the size of their parents'
D) offspring with enhanced homozygosity
E) a reduction in the number of offspring with undesirable traits
Which one of the following does not occur during mitotic anaphase?
A) The centromeres of each chromosome divide.
B) Daughter chromosomes begin to move toward opposite poles of the cell.
C) The chromatid DNA replicates.
D) Sister chromatids separate.
E) All of the choices occur during mitotic anaphase.
Cancer is not usually inherited because
A) the causes of cancer are not usually genetic.
B) people with cancer usually die before reproducing.
C) the chromosomal changes in cancer are usually confined to somatic cells.
D) cancer typically causes disruptions of meiosis.
E) the cancerous cells usually interfere with the ability to produce gametes.
cells that do not respond normally to the cell cycle control system; they divide excessively and can invade other tissues of the body
cancers that originate in the external or internal covering of the body, such as the skin or lining of the intestine
an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell into two cells
cell cycle control system
a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.
Which one of the following is a difference between sexual and asexual reproduction?
A) Sexual reproduction includes the development of unfertilized eggs.
B) Sexual reproduction produces more offspring.
C) Regeneration is exclusive to sexual reproduction.
D) Sexual reproduction is more likely to increase genetic variation than is asexual reproduction.
E) Asexual reproduction always increases the number of sets of chromosomes in the offspring; sexual reproduction decreases the number of sets of chromosomes in the offspring.
Virchow's simple and profound principle, stated formally in 1858, was that
A) photosynthesis is the center of all life.
B) animals must always reproduce.
C) animals must develop.
D) all cells come from cells.
E) all life evolves.
Which of the following occurs during interphase?
A) growth of the aster
B) duplication of the chromosomes
C) cell growth
D) cell growth and duplication of the chromosomes
E) None of the choices are correct.
You are the director of research for a drug company. The following list of candidate drugs is brought to you. Which is the most likely to be worth developing as a cancer chemotherapy agent? A drug that
A) prevents tetrad formation.
B) causes cells to divide at a right angle from their usual orientation.
C) prevents crossing over.
D) prevents sister chromatids from separating at anaphase. E) interferes with cellular respiration.
Which of the following is probably the main factor responsible for the phenomenon of density-dependent
A) a local accumulation of growth-inhibiting factors
B) cells' innate "sense" of knowing when the organ of which they are a part has no need for additional cells
C) a local deficiency of nutrients
D) the absence of growth factors E) None of the choices are correct.
Independent orientation results in an increase in the number of
A) homologous chromosomes.
C) sex chromosomes.
D) possible combinations of characteristics.
E) points of crossing over.
if a fragment from one chromosome joins to a sister chromatid or homologous chromosome it will produce a:
Which of the following is likely to account for the difference between plant and animal cell cytokinesis?
A) Plant cells have two sets of chromosomes; animal cells have one set of chromosomes.
B) Plant and animal cells do not have a common ancestor.
C) Animal cells lack chloroplasts.
D) Plant cells lack the microfilaments required for forming a cleavage furrow.
E) Plant cell division must maintain the integrity of the cell wall.
the production of gene combinations different from those carried by the original chromosomes
two chromosomes composing a pair that carry genes controlling the same inherited characteristics
a growing phase in which the cell roughly doubles everything in its cytoplasm and precisely duplicates its chromosomal DNA and the actual cell division
an ordered display of magnified images of an individual's chromosomes arranged in pairs, starting with the longest
leukemia and lymphoma
cancers of blood forming tissues, such as bone marrow, spleen, and lymph nodes (two answers)
development, from a fertilized egg to a new adult organism, is one phase of multi-cellular organisms.
at this phase, the mitotic spindle is fully formed, with its poles at opposite ends of the cell. The chromosomes convene on the metaphase plate, an imaginay plane equidistant between the two poles of the spinfle. The centromeres of all the chromosomes are lines up on the metaphase plate. For each chromosome, the the kinetichores of the two sister chromatids face opposite poles of the spindle. The mocrotubules attached to a particular chromatid all come from one pole of the spindle, and those attached to its sister chromatid come from the opposite end.
stage in which doubled chromosomes move to the equator of the spindle and chromatids are attached by centromeres to a separate spindle fiber
in this stage, the nucleus and its ontents, including the duplicated chromosomes, divide and are evenly distributed to form two daughter cells.
a football shaped structure of microtubules that guides the separation of two sets of daughter chromosomes
stage in which duplicated chromosomes condense from chromatin, and the mitotic spindle forms and begins moving the chromosomes toward the center of the cell.
during this phase, changes occur in both the nucleus and cytoplasm. Within the nucleus, the chromatin fibers become more tightly coiled and folded, forming discrete chromosomes that can be seen with the light microscope. The light nucleoli disappear. Each duplicated chromosome appears as two identical sister chromatids joined together, with a narrow "waist" at the centromere. In the cytoplasm, the mitotic spindle begins to form as microtubules rapidly grow out from the centrosomes, which begin to move away from each other.
stage in which the chromosomes reach the spindle poles, nuclear envelopes form around each set of daughter chromosomes, and the nucleoli reappear