A type of horizontal gene transfer in prokaryotes, in which a cell takes up naked DNA without cell-to-cell contact, is
A. transduction. B. fixation.
C. conjugation.
D. transformation.
E. replication.
D. transformation.
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You're a famous eye surgeon, specializing in corneal transplants. Give your choice, would you rather have a cornea for transplantation from a 20 year old individual, or a 60 year old individual (assuming there are no optical defects due to age), and why?
A. The 60 year old-clearly, if the individual has gone 60 years with no optical defects, this is a very good organ for transplantation. The 20 year old cornea may have defects that simply haven't become apparent yet. B. The 20 year old cornea-younger is always better when dealing with tissue transplants. You want to give the transplant the longest possible time for survival in the recipient. C. The 20 year old cornea-while extremely rare, it may be possible to transmit prions through corneal transplants. It's less likely that a 20 year old would have encountered and become contaminated by prions than the 60 year old. D. The 20 year old cornea-never mind prions, there are a variety of agents that can hide in corneal tissues and that might cause disease. It's far more likely that the 60 year old would be harboring one or more of these pathogens than the 20 year old.
The rotation of Earth on its axis is the driving force behind the water cycle
Indicate whether the statement is true or false
Which cell plays a central role in all adaptive immune responses?
A. Dendritic cell B. Mast cell C. Basophils D. NK cell E. T cell
Which of the following does not act to increase the amount of calcium in the blood?
A. kidneys B. intestines C. calcitonin D. bones E. parathyroid hormone