A 39-year-old woman is in her sixth week of pregnancy. Due to her advanced age, she is at higher risk for having a baby with Down's syndrome than younger pregnant women. She would like to find out as early as possible whether or not her baby has Down's syndrome. Her doctor should suggest
A. amniocentesis.
B. genetic counseling.
C. chorionic villi sampling.
D. a pedigree analysis.
C. chorionic villi sampling.
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With the exception of some gram-positive cocci, what concentration of NaCl inhibits nearly
A) 2.5% B) 5% C) 7.5% D) 10%
Concerning the sex chromosomes, which of the
following is correct? a. The Y chromosome carries a greater number of genes for nonsexual traits than does the X. b. X and Y are different in size but carry nearly equal numbers of genes. c. The X chromosome carries more genes for nonsexual traits than does the Y. d. The X chromosome carries only gender-related genes. e. The X chromosome carries the SRY gene.
Two contraceptive methods that are generally irreversible and which block the gametes from moving to a site where fertilization can occur are _____
A) the male condom and female condom B) the male condom and oral contraceptives C) vasectomy and tubal ligation D) the diaphragm and subcutaneous progesterone implant
Choose the true statements about molecular clocks.
A. Ultimately, all molecular clocks depend on the rate of DNA mutation and DNA repair mechanisms. B. The rate of a molecular clock for a given DNA character might vary depending on how constrained the character is by natural selection. C. Molecular clocks can be calibrated using fossil evidence. D. All molecular clocks tick at the same rate.