«DBQ on p. 58 – October 26, 2012»
1) Compare the base composition of Mycobacterium tuberculosis (a prokaryote) with
the base composition of the eukaryotes shown in the table.
Compared to the eukaryotes, the base composition of Mycobacterium
tuberculosis composed more of guanine and cytosine and less of adenine and
thymine.
2) Calculate the base ratio A+ G/T +C, for humans and for Mycobacterium tuberculosis.
Show your working.
Base ratio A+ G/T +C for humans
Adenine + Guanine : Thymine + Cytosine
31.0 + 19.1 : 31.5 + 18.4
50.1 : 49.9
Base ratio A+ G/T +C for Mycobacterium tuberculosis
Adenine + Guanine : Thymine + Cytosine
15.1 + 34.9 : 14.6 + 35.4
50.0 : 50.0
3) Evaluate the claim that in the DNA of eukaryotes and prokaryotes the amount of
adenine and thymine are equal and the amounts of guanine and cytosine are equal.
The data provided both does and does not support this claim. With the
exception of the Mycobacerium tuberculosis, the prokaryotes and eukaryotes are both
primarily composed of adenine and thymine; this supports the statement. However,
the opposite occurs in Mycobacterium tuberculosis, which is primarily composed of
guanine and cytosine (instead of adenine and thymine, like in eukaryotes).
4) Explain the ratios between the amounts of bases in eukaryotes and prokaryotes in
terms of the structure of DNA.
The ratios between the amounts of bases in eukaryotes and prokaryotes are
mostly very similar. In order for this to happen, the complementary base pairings that
occur in prokaryotes and eukaryotes must also be very similar. This means that the
structure of the DNA (in terms of the complementary base pairs) of eukaryotes and
prokaryotes are very similar.
5) Suggest reasons for the difference in the base composition of bacteriophage T2 and
the polio virus.
The reasons for the difference in the base composition of bacteriophage T2
and the polio virus could be because of ways they are structured. The genetic
information of the bacteriophage T2 is stored in double-stranded DNA, whereas the
genetic information of the polio virus is stored in single-stranded RNA.