Question

The DNA from two different species can often be distinguished by a difference in the

(a) ratio of A + T to G + C.
b) ratio of A + G to C + T.
(c) ratio of sugar to phosphate.
(d) presence of bases other than A, G, C, and T. (e) number of strands in the helix.

Answer 1

DNA from different species can be distinguished by the ratio of A+T to G+C, reflecting Chargaff's rule of base pairing where adenine pairs with thymine, and cytosine pairs with guanine. The strands are anti-parallel within the DNA helix structure.

Step-by-step explanation:

The DNA from two different species can often be distinguished by a difference in the ratio of A + T to G + C. This reflects Chargaff's rule, which states that the amount of adenine (A) is approximately equal to the amount of thymine (T), and the amount of guanine (G) is approximately equal to the amount of cytosine (C), maintaining a consistent A+T/G+C ratio within any given species. DNA is made up of two strands forming a helix with the bases adenine, thymine, cytosine, and guanine.

Adenine pairs with thymine through two hydrogen bonds, and cytosine pairs with guanine through three hydrogen bonds, establishing base pairing. The two strands of the DNA helix are anti-parallel, meaning the 3' end of one strand faces the 5' end of the opposite strand.