Chapter 8 stuff.

The creation of genetically identical offspring by a single parent, without the participation of sperm and egg, is calledasexual reproduction.
Which of the following statements regarding sexual and asexual reproduction is true?Sexual reproduction is more likely to increase genetic variation than is asexual reproduction.
Asexual reproduction requires ________ individual(s).1
With the exception of identical twins, siblings who have the same two biological parents are likely to look similar, but not identical, to each other because they havea similar but not identical combination of genes.
Which of the following statements regarding cell division is false?Cell division is common in eukaryotes but rare in prokaryotes.
Which of the following statements regarding prokaryotes is false?Prokaryotic chromosomes are more complex than those of eukaryotes.
Eukaryotic chromosomes differ from prokaryotic chromosomes in that theyare housed in a membrane-enclosed nucleus.
Sister chromatids arejoined together at a centromere.
Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures calledsister chromatids.
Eukaryotic cells spend most of their cell cycle in which phase?interphase
Which of the following occurs during interphase?cell growth and duplication of the chromosomes
The genetic material is duplicated duringthe S phase.
Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! Then you realize that this cell isundergoing cytokinesis.
The phase of mitosis during which the mitotic spindle begins to form isprophase
During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles?metaphase
At the start of mitotic anaphase,the centromeres of each chromosome come apart.
During which phase of mitosis does the nuclear envelope re-form?telophase
Which of the following is a feature of plant cell division that distinguishes it from animal cell division?formation of a cell plate
Which of the following must occur for a plant or animal to grow and develop normally?The organism must be able to control the timing and rate of cell division in different parts of its body.
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 ofdensity-dependent inhibition.
As a patch of scraped skin heals, the cells fill in the injured area but do not grow beyond that. This is an example ofdensity-dependent inhibition.
Mature human nerve cells and muscle cellsare permanently in a state of nondivision.
Which of the following statements regarding the cell-cycle control system is false?The cell-cycle control system operates independently of the growth factors.
You are asked to culture an unidentified sample of animal tissue. You notice that the cells seem to fail to exhibit density-dependent inhibition. The source of this tissue sample is most likelya cancer.
A benign tumor differs from a malignant tumor in that a benign tumordoes not metastasize.
Which of the following shows the greatest promise as a cancer chemotherapy agent?a drug that prevents mitotic spindle from forming
Two chromosomes in a nucleus that carry genes controlling the same inHerited characteristics areHomologous chromosomes.
Which of the following statements is false?An X chromosome is an autosome.
During which stage of meiosis do synapsis and crossing over occur?prophase I
Both mitosis and meiosis are preceded byinterphase
Independent orientation of chromosomes at metaphase I results in an increase in the number ofpossible combinations of characteristics.
Karyotypingcan reveal alterations in chromosome number.
Which of the following statements regarding Down syndrome is false?Down syndrome is least likely to be seen in the infants of mothers over 40.
Nondisjunction occurs whenmembers of a chromosome pair fail to separate.
Which of the following statements about nondisjunction is false?In mammals, extra copies of the Y chromosome are typically inactivated.
If a chromosome fragment breaks off and then reattaches to the original chromosome, but in the reverse direction, the resulting chromosomal abnormality is called a(n)inversion
According to the graph, at what maternal age does the incidence of Down syndrome begin to increase substantially?about 37 or 38
Cancer is not usually inherited becausethe chromosomal changes in cancer are usually confined to somatic cells.
Which of the following variations of the sentence “Where is the cat” is most like a chromosomal deletion?Where is cat?
A karyotype is most likephotographs of every couple at a high school prom.
If these four cells resulted from cell division of a single cell with diploid chromosome number 2n = 4, what best describes what just occurred?nondisjunction
What type of cell is shown?plant cell in telophase
The process by which the cytoplasm of a eukaryotic cell divides to produce two cells is calledcytokinesis
Which of the following features likely accounts for the difference between plant and animal cell cytokinesis?Plant cells have cell walls.
Which of the following is probably the main factor responsible for the phenomenon of density-dependent inhibition?physical contact of cell-surface proteins between adjacent cells
Which of the following statements regarding the function of mitosis is false?Mitosis allows organisms to generate genetic diversity.
Which of the following statements regarding the differences between mitosis and meiosis is false?Crossing over is a phenomenon that creates genetic diversity during mitosis.
Without crossing overgenetic recombination could not occur.