Which is true concerning cell division?
A. During meiosis I, sister chromatids pair up and then are separated
B. An asexually reproducing organism needs mitosis to produce a genetically diverse set of daughter cells in order to maintain genetic diversity
C. When comparing the parent and daughter cells, meiosis differs in both the ploidy level and ploidy number, whereas mitosis differs in neither
D. During crossing over, an allele for brown eyes may be switched with an allele for brown hair
Ans: A. During meiosis I, sister chromatids pair up and then are separated
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The ELISA test has been used as the most common, rapid screening test for HIV infection. Its sensitivity is very high but its specificity is rather low (for an important identification test). Which statement describes this accurately?
A. A false positive test result may develop due to the test antigens capturing normal antibodies. B. The patient's specimen has to be handled in a certain way to maintain the integrity of the viral DNA. C. The test can identify the patient's antibody to HIV only when it is large quantities. D. Only certain kinds of instruments can be used to pick up the small amounts of fluorescence given off in the ELISA.
Why is surface area to volume ratio important
for all cells?
a. a cell must be small enough to absorb small molecules and atoms b. if a cell has too small a surface area, the surface to volume ratio will be too large c. if a cell has too large a surface area to volume ratio, the plasma membrane is not sufficient to deal with the increased amount of cytoplasm d. surface area to volume ratios are only important for small cells, like bacteria e. more than one of these is correct
A fibrocartilage callus is formed in the process of bone repair.
a. true b. false
During a human pregnancy, implantation occurs at which stage?
a. zygote b. early cleavage c. blastocyst d. gastrula e. morula