1. Which of the following are characteristics of theWatson-Crick
DNA double helix? (there are more than one answer)
a. The two polynucleotide chains are coiled about a common
axis.
b. Hydrogen bonds between A and C and between G and T hold
the two chains together.
c. The purines and pyrimidines are on the inside of the
helix and the phosphodiester backbones are on the
outside.
d. Base composition analyses of DNA duplexes isolated from
many organisms have shown that the amounts of A and T are
equal as are the amounts of G and C.
e. The sequence in one strand of the helix varies
independently of that in the order strand.
2. Which of the following statements about reversetranscriptase
are correct (there are more than one answer,5 points)
a. Reverse transcriptase uses DNA as a template tosynthesize
DNA.
b. Reverse transcriptase uses RNA as a template tosynthesize
RNA.
c. Reverse transcriptase uses DNA as a template tosynthesize
RNA.
d. Reverse transcriptase is found in the virions of all RNA
tumor viruses.
e. Reverse transcriptase hydrolyzes RNA in DNA-RNA hybrid
duplexes.
3. Several dozen oncogenes are known to code for receptortyrosine
kinases. Many of these oncogenes produce mutant receptors,
whose tyrosine kinase activity is permenantly activated,this
is called,(5 points)
a. Autophosphorylation
b. Constitutively active
c. Growth factor dependency
d. a,b,c
e. None of the above
