Multiple Choice
Why is DNA replication referred to as semiconservative?
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14. DNA Synthesis
Introduction to DNA Replication
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Why does a DNA strand grow only in the 5' to 3' direction during replication?
A
Because the 5' end of the DNA strand is chemically reactive.
B
Because DNA polymerase can only add nucleotides to the 3' end of the growing strand.
C
Because the 3' end of the DNA strand is chemically inert.
D
Because DNA polymerase can only add nucleotides to the 5' end of the growing strand.
Verified step by step guidance1
Understand the structure of a DNA strand: DNA strands have a directionality, with one end labeled 5' (five prime) and the other 3' (three prime). This refers to the carbon numbers in the DNA's sugar backbone.
Recognize the role of DNA polymerase: DNA polymerase is the enzyme responsible for adding nucleotides to a growing DNA strand during replication.
Identify the directionality of DNA polymerase activity: DNA polymerase can only add new nucleotides to the 3' end of the growing DNA strand. This is because the enzyme requires a free hydroxyl group (-OH) at the 3' carbon to form a phosphodiester bond with the incoming nucleotide.
Understand the chemical reaction involved: The addition of a nucleotide involves the formation of a phosphodiester bond between the 3' hydroxyl group of the last nucleotide in the chain and the 5' phosphate group of the incoming nucleotide.
Conclude why DNA synthesis occurs in the 5' to 3' direction: Since DNA polymerase can only add nucleotides to the 3' end, the DNA strand grows in the 5' to 3' direction, ensuring the correct and efficient replication of DNA.
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