Question

Consider these sentences regarding the structure and nature of DNA.

I. DNA has two pyrimidine bases that contain single ring structure.
II. In DNA, composition of bases should be $\frac{A+T}{G+C}=1$.
III. Each base pair of DNA is $3.4\stackrel{o}{A}$ apart from other base pairs.
IV. The nucleosome model DNA packaging was proposed by Kornberg and Thomas.

Choose the correct statements from the given options.

• A. I and III
• B. I, II and III
• C. II, III and IV
• D. I, III and IV

Answer 1

The correct option is D I, III and IV

Erwin Chargaff$\left(1950\right)$ made a quantitative analysis of DNA and showed that the composition of DNA molecules varies in complex ways depending upon the source of DNA. He proposed Base Equivalence rule or Chargaff's rule, which states that, for double-stranded DNA, the proportion of adenine always equals the thymine and the proportion of guanine always equal to that of cytosine, i.e., $A=T$ and $G=C$.
It follows that an equal proportion of purines and pyrimidines is always seen in a double-stranded DNA, i.e.,
$A+G=T+C$ or $\frac{A+G}{T+C}=1$.
The pyrimidine bases like thymine and cytosine have a single nitrogen ring.
The total length of the DNA strand 340angstrom and the number ofbase pairs in each turn is 10 base pairs. So, each base pair of DNA is 3.4angstromapart.
The nucleosome model DNA packaging was proposed by Kornberg and Thomas.
So, the correct answer is option D.