xBookUtils.showAnswers['phelan3e-ch6-THMCQ-1'] = "
Telomeres are sections of DNA at the tips of each chromosome. They shorten with each division, and when they get too short the cell can die.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-2'] = "Prokaryotes have a single circular chromosome that is attached at one site to the cell membrane, whereas eukaryotic cells have free-floating linear chromosomes within a cell nucleus. The eukaryotic chromosome is made up of chromatin, a linear DNA strand that is bound to and wrapped around histones, which are proteins that keep DNA from getting tangled and enable it to be packed inside the nucleus in an orderly way.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-3'] = "The division of a cell involves both mitosis and cytokinesis. Mitosis is a process in which the nucleus of the parent cell duplicates, while cytokinesis is a process during which the remainder of the cell duplicates.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-4'] = "The two strands of a double-stranded DNA molecule unzip, and a new DNA strand is produced opposite each of these two separated strands.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-5'] = "As organisms get bigger, growth happens in part through the creation of new cells through mitosis. Mitosis is also responsible for the replacement of cells when they die.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-6'] = "First, chromosomes condense. Then, chromosomes line up in the middle of the cell. Next, duplicate versions of chromosomes separate. Finally, each set of chromosomes is surrounded by a new nuclear membrane.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-7'] = "At the beginning of interphase, each chromosome contains one long double-stranded DNA molecule. During interphase, DNA replication occurs, and each chromosome then contains two long double-stranded DNA molecules. These paired structures are called sister chromatids, and are eventually separated during anaphase of mitosis to form two separate but identical chromosomes.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-8'] = "Normal cells divide only a finite number of times, but cancer cells can divide indefinitely. Cancer cells also lose their \"contact inhibition,\" which would normally suppress growth once cells bump up against other cells. The membranes of cancer cells have reduced adhesiveness, causing them to stick to one another less than non-cancerous cells.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-9'] = "Offspring produced by sexual reproduction receive chromosomes from two, separate individuals; therefore, these two, separate individuals must be able to produce cells that have half as many chromosomes as the rest of their cells. When these cells, called gametes, combine during fertilization, the full number of chromosomes is restored.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-10'] = "During metaphase I, homologous pairs of chromosomes move toward the center of the cell (referred to as the metaphase plate) and line up. In anaphase I, the homologues separate and are pulled to opposite poles of the cell. The sister chromatid pairs are pulled to the ends of the cell at random, resulting in a mix of maternal and paternal genetic material. In metaphase II, sister chromatid pairs line up at the center of the cell. Then, sister chromatids are pulled apart by spindle fibers toward opposite poles of the cell in anaphase II.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-11'] = "During the formation of male and female gametes (sperm and egg, respectively), the segregation of chromosomes is similar, but the division of the cytoplasm is not. Cytoplasm is divided equally into four gametes during sperm production; however, in egg production, nearly all of the cytoplasm is concentrated into a single egg.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-12'] = "Crossing over between homologous chromosomes increases genetic variation not by producing new traits, but by producing new combinations of traits.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-13'] = "Asexual reproduction is fast and easy, and the resulting offspring carry all of the genes of the parent. Sexual reproduction increases genetic variation in a population, which allows populations to better adapt to a changing environment.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-14'] = "Females possess two X chromosomes, while males possess one X chromosome and one Y chromosome.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-15'] = "In both birds and humans, one gender has two identical sex chromosomes, and one gender has two nonidentical sex chromosomes. However, the gender with nonidentical sex chromosomes is males in humans (XY) and females in birds (WZ).
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-16'] = "Species with temperature-dependent sex determination could be negatively impacted by an increase of even a few degrees, as this could result in no male offspring being produced.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-17'] = "Nondisjunction is the unequal distribution of chromosomes during meiosis, and can occur at two different points; homologous chromosomes can fail to separate during anaphase I, or sister chromatids can fail to separate during anaphase II. In either case, some or all of the gametes produced will have an inappropriate number of chromosomes.
"; xBookUtils.showAnswers['phelan3e-ch6-THMCQ-18'] = "XYY individuals have normal fertility, while X_, XXY, and XXX individuals are generally sterile.
";