How have Caesarean sections and intensive neonatal (near-birth) medical care likely affected the average birth weight of American babies?
A) Stabilizing selection for birth weight no longer has as much of an influence.
B) Average birth weights have significantly decreased.
C) Gene flow will occur in the direction of larger and smaller infants.
D) Birth weight is now subject to disruptive selection instead of stabilizing selection.
Answer: A
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The first oncogene to be discovered:
A. is a gene that contributes to uncontrolled cell division or cancer. B. was first discovered in a Rous sarcoma virus that causes cancer. C. is a protein kinase that acts as a cell division trigger. D. has a less-active normal counterpart called a proto-oncogene. E. All of these choices are correct.
Which of the following is not true of oligonucleotide-directed mutagenesis?
A. Two complementary oligonucleotides, each identical in sequence to the cloned gene, are annealed to the opposite strands of the cloned gene. B. Two complementary oligonucleotides, each with the desired base change, are annealed to the opposite strands of the cloned gene. C. After repeated cycles of PCR, the mutation containing DNA predominates in the population. D. Nonmutant template plasmid DNA can be selectively eliminated by cleavage of the methylated template strand. E. The two annealed mutant DNA strands serve as primers of DNA synthesis in both directions around the plasmid vectors.
In gene regulation and control, repression is defined as the:
a. internal change in the original nucleotide sequence of a gene or genes within an or-ganism's genome. b. mechanism of genetic control in which genes are induced only when the substrate to be degraded by enzymatic action is present. c. change of the bacterial genotypes through the exchange of DNA from one cell to another. d. mechanism of genetic control in which genes are not transcribed and therefore are not expressed in the presence of those target products in sufficient supply.
Which of the following serves as a physical barrier to prevent the sperm cell from getting to the egg cell?
A. abortion B. IUD C. condom D. spermicidal jelly