What is the genetic function of restriction enzyme?
A. adds new nucleotides to the growing strand of DNA
B. joins nucleotides during replication
C. repairs breaks in sugar-phosphate backbones
D. joins nucleotides during transcription
E. cleaves nucleic acids at specific sites
Ans: E. cleaves nucleic acids at specific sites
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Which term did Mendel use when referring to traits that disappeared in the F 1 generation?
a. recessive b. discontinuous c. reciprocal d. continuous
In a biology lab exercise, you are asked to examine cells of a growing onion root tip that has been sectioned to show many cells. In most of the cells, you easily see the circular or oval nucleus as a uniformly filled space in a membrane outline. In a small percentage of cells, you see chromosomes as distinct strands just as cell division begins, and as it progresses, because the chromatin
A. becomes less tightly wound, to facilitate cell division.
B. increases in length, as replication adds DNA sections to the original.
C. becomes more tightly folded, increasing their visible length.
D. becomes less tightly folded, increasing their visible length.
E. becomes more tightly wound, to protect DNA, and to more easily manage cell division.
The steep increase in human population at point “C” indicates the beginning of the ____
a. Bubonic plague b. domestication of plants and animals c. industrial and scientific revolutions d. discovery of America e. emergence of agriculturally based urban societies
The Ogallala aquifer provides what percentage of groundwater used for irrigation in the United States?
a. 10 percent b. 25 percent c. 30 percent d. 50 percent e. 75 percent