During in vitro synthesis of DNA, a researcher used 2', 3'-dideoxy cytidine triphosphate as raw nucleotide in place of $2^{\prime}$-deoxy cytidine. What would be the consequence?
Further polymerisation would not occur, as the $3^{\prime} \mathrm{OH}$ on sugar is not there to add a new nucleotide for forming ester bond.
That background information did Watson and Crick have made available for developing a model of DNA? What was their contribution?
Watson and Crick had the following informations which helped them to develop a model of DNA.
(i) Chargaff's Law suggesting $\mathrm{A}=\mathrm{T}$ and $\mathrm{C}=\mathrm{G}$
(ii) Wilkins and Rosalind Franklin's work on DNA crystal's X-ray diffraction studies about DNAs physical structure.
Watson and Crick proposed
(a) Pattern of complementary bases pair
(b) Semi-conservative replication
(c) Mutation through tautomerism
What are the functions of
(i) methylated guanine cap?
(ii) poly-A 'tail' in a mature on RNA?
(i) Methylated guanine cap helps in binding of $m$ RNA to smaller ribosomal sub-unit during initiation of translation.
(ii) Poly-A tail provides longevity to $m$ RNA's life. Tail length and longevity of $m$ RNA are positively correlated.
Do you think that the alternate splicing of exons may enable a structural gene to code for several isoproteins from one and the same gene? If yes, how? If not, why so?
Functional mRNA of structural genes need not always include all of its exons. This alternate splicing of exons is sex-specific, tissue-specific and even developmental stage-specific. By such alternate splicing of exons, a single gene may encode for several isoproteins and/ or proteins of similar class.
In absence of such a kind of splicing, there should have been new genes for every protein/isoprotein. Such an extravagancy has been avoided in natural phenomena by way of alternate splicing.
Comment on the utility of variability in number of tandem repeats during DNA fingerprinting.
Tandemness in repeats provides many copies of the sequence for finger-printing and variability in nitrogen base sequences present in them. Being individual-specific, this proves to be useful in the process of DNA fingerprinting.