In humans, the "master sex switch" that determines whether an embryo will become a male is the
a. X chromosome.
b. locus.
c. SRY gene.
d. androgen switch.
c. SRY gene.
You might also like to view...
Researchers trying to cure a deadly virus have discovered that it can only infect cells that display specific carbohydrate chains on their exterior plasma membrane. An early drug trial incorporated an enzyme designed to digest all carbohydrates outside the cell. Researchers believed that without those carbohydrate markers, the virus would not be able to identify vulnerable cells. When tested, the drug caused massive tissue damage instead. What mistake did the researchers make?
a. They forgot that the primary component of plasma membranes is carbohydrates; the drug destroyed the cells’ membranes. b. Without their carbohydrate markers, the cells were identified by antibodies as being foreign and were destroyed. c. Carbohydrates attached to the plasma membrane also bind cells together; without them, the tissues fell apart. d. The enzymes released carbohydrates into the intercellular medium, allowing the virus to replicate faster.
As the Baby Boomer generation ages, more and more joint replacement surgeries take place each year. Hip replacement surgery is the gold standard of all joint replacement surgeries, with many patients able to walk just a few hours after surgery and return home the very next day. In contrast, knee replacement surgery usually requires hospital stays of several days, followed by weeks to months of physical therapy. What best explains why the recovery after hip replacement surgery is so much faster than after knee replacement surgery?
A. The hip only moves in one direction, and recovery of one motion is easier than recovering movement in many directions. B. The upper end of the thigh bone has less overall surface contact with the hip bone than its lower end has in the knee with bones of the lower leg. C. The knee is a type of combination joint, which are difficult to replace. D. The knee joint is stabilized by many more structures (many of which have to be cut) than the hip joint. E. The hip joint is more superficial and more accessible to surgeons than the knee joint.
Parietal cells secrete pepsinogen. Indicate whether the statement is true or false
Answer the following questions true (T) or false (F)
1. State whether the following statement is true or false, then give your reasoning. The terminating "hairpin" loop occurs in the trp operon when sufficient tryptophan is present.