Question

The base sequence in one of the strands of DNA is TAGCATGAT 

(i) Give the base sequence of its complementary strand. 

(ii) How are these base pairs held together in a DNA molecule ? 

(iii) Explain the base complementarity rules. Name the scientist who framed this rule.

Answer 1

(i) ATCGTACTA 

(ii) Through Hydrogen bonds, between A and T and C and G on the two strands. 

(iii) A = T and C = G, Watson and Crick/ Chargaff.

Detailed Answer: 

(i) ATCGTACTA. 

(ii) The base pairs are held together in a DNA molecule by hydrogen bond in such a way that Adenine (A) pairs with Thymine (T) by two Hydrogen bonds (A = T) and Guanine pairs with Cytosine (C) by three Hydrogen bonds (C = G). 

(iii) The base complementarity rule is that the ratios between adenine-thymine and guanine-cytosine are constant and equal to one. The scientists who framed this rule are Erwin Chargaff and Watson and Crick.