Read the given passage and answer the following questions:
The Matthew Meselson and Franklin Stahl experiment was to prove that DNA replicates semiconservatively. It was shown first in Escherichia coli and subsequently in higher organisms, such as plants and human cells. The scheme suggested that the two strands would separate and act as a template for the synthesis of new complementary strands. After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand. This scheme was termed as semiconservative DNA replication. Very similar experiments involving use of radioactive thymidine to detect distribution of newly synthesised DNA in the chromosomes was performed on Vicia faba (faba beans) by Taylor and colleagues in 1958. The experiments proved that the DNA in chromosomes also replicate semiconservatively.
The main enzyme of DNA replication uses a DNA template to catalyse the polymerisation of deoxynucleotides. What is it called?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → DNA-dependent DNA polymerase
DNA replication needs a set of enzymes. The main enzyme builds the new strand by joining deoxynucleotides, and it reads an existing DNA strand as the template. Because its template is DNA and its product is DNA, it is called DNA-dependent DNA polymerase. It works very fast and with high accuracy.
NCERT Extract:
The Machinery and the Enzymes – “In living cells, such as E. coli, the process of replication requires a set of catalysts (enzymes). The main enzyme is referred to as DNA-dependent DNA polymerase, since it uses a DNA template to catalyse the polymerisation of deoxynucleotides. These enzymes are highly efficient enzymes as they have to catalyse polymerisation of a large number of nucleotides in a very short time.”