Short Answer TypeThe 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.
(i) The base sequence of the complementary strand will be - ATCGTACTA.
(ii) The base pairs in the DNA molecules are held together by hydrogen bonds. There are two hydrogen bonds between adenine and thymine and three hydrogen bonds between guanine and cytosine.
(iii) Base Complementarity Rule: A purine always pairs with a pyrimidine in a DNA molecule i.e.
A will pair with T and G will pair with C.
The ratio of A and T or C and G will always be 1.
Erwin Chargaff framed the base complementarity rule.
Long Answer TypeDescribe how the lac operon operates, both in the presence and absence of an inducer in E.coli.
Short Answer Type(a) Draw a neat labelled diagram of a nucleosome.
(b) Mention what enables histones to acquire a positive charge.Long Answer TypeDescribe Frederick Griffith’s experiment on Streptococcus pneumonia. Discuss the conclusion he arrived at.
Short Answer TypeFollowing are the features of genetic codes. What does each one indicate ? [2]
Stop codon; Unambiguous codon; Degenerate codon; Universal codon.
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