This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “The Experimental Proof of Replication of DNA”.
1. When the process of replication is over, each DNA molecule will end up with one parental and one newly synthesised strand.
Explanation: The double helical structure of the DNA molecule possesses two strands. It is separated during the process of replication. The separate strands will act as templates for the synthesis of complementary strands. So, when the process of replication comes to an end, every DNA molecule has a parental and newly synthesised strand.
2. Which process is termed as “semiconservative DNA replication”?
a) Presence of only newly synthesised strands in DNA
b) Presence of only parental strands in DNA
c) Presence of both parental and newly synthesised strands in DNA
d) Presence of a hybrid variety of strands
Explanation: The term semiconservative DNA replication means that the DNA molecule has both a parental and newly synthesised strand by the process of replication. During replication, the template strand of the DNA (the separated strand from the double helical structure) will help in the synthesis of complementary strands.
3. In which organism was the “Semiconservative theory of DNA replication” first observed?
a) Treponema pallidum
b) Vibrio cholerae
c) Staphylococcus pneumoniae
d) Escherichia coli
Explanation: It was proved by Watson and Crick that the DNA replicates semi-conservatively. This was first observed in Escherichia coli. Later, the same concept was observed in plants and human cells too.
4. Which of the following is the heavy isotope of nitrogen?
Explanation: Mathew Meselson and Franklin Stahl grew Escherichia coli in a medium containing 15NH4Cl as the only source of nitrogen for many years together. The isotope of nitrogen in this compound is 15N. It is said to be the heavy isotope of nitrogen.
5. Which organism was used to detect the presence of thymidine on the newly formed DNA in 1958?
a) Vivrio cholerae
b) Treponema pallidum
c) Vicia faba
d) Escherichia coli
Explanation: Taylor and his colleagues conducted an experiment on Vicia fabain 1958. They used radioactive thymidine to detect the distribution of newly synthesised DNA in the chromosomes of the cells. They proved that the DNA which is present inside the chromosomes replicate semi conservatively.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
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