Which of the following best describes the nature of the cells of mature, functioning xylem?
A) dead, thick-walled tubes
B) living cells that have lost their nucleus
C) dead cells that retain some organelles and some maintenance functions
D) living, thick-walled tubes
Answer: A
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Chemical messengers produced by endocrine glands are called
a. agonists b. neurotransmitters c. hormones d. enzymes
Which of the following is NOT a part of the MAP kinase pathway? (Select all correct choices.)
A. A receptor kinase is activated by binding to a growth factor and phosphorylates receptor cytoplasmic domains. B. The activated receptor kinase dimer activates the RAS protein to bind to a GTP. C. The activated RAS protein activates protein kinases in the signal-transduction pathway. D. A series of protein kinases amplify the signal to the nucleus where genes responsible for cell division are switched on. E. A pyrophosphatase enzyme terminates the cellular response.
Genetic counselors are typically medical doctors who specialize in treating infertile couples
a. True b. False Indicate whether the statement is true or false
The FBI currently determines an individual's DNA profile using:a
DNA sequencing. b. mitochondrial DNA variations. c. RFLPs. d. DNA ligation. e. 13 STR markers.