34. In Sanger's method of DNA sequencing, the growing DNA chains are terminated
because :
(A) DNA polymerase is not very processive
(B) A radioactive nucleotide is incorporated
(C) The substrates become limiting
(D) A phosphodiester bond cannot be made
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Answers
(A) Most DNA polymerases are intrinsically low- processivity enzymes despite some noticeable exceptions, such as the phage Φ29 DNA polymerase. Processivity is defined as the ability of DNA polymerase to carry out continuous DNA synthesis on a template DNA without frequent dissociation
(B) The three parts of the nucleotide building block of DNA are the sugar, the base and the phosphate. The complex of the sugar with the base is called a nucleoside. Darshan Senthil. Feb 19, 2015. So radioactive DNA probes are basically single strands of DNA or RNA with a radioactive tag. Their sequence is usually the complementary of a single sequence of DNA that researchers want to find in an array of other DNA (such as a gene). So they tag this probe, and release it.
(C) A nutrient used in the growth of micro organims in a concentration that restricts or limits the rate of growth. Where another nutrient is the limiting substrate, other undesirable bioproducts may result or there may be a poor growth of cells.
(D) A phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. An example is found in the linking of two pentose (5 carbon sugar) rings to a phosphate group by strong, covalent ester bonds.
Answer:
D
Explanation:
S phosphodiaster bond can not be made