Question

question 6
at the end of dna replication, two dna molecules are produced, each one consisting of a parental dna strand and a new dna strand. known as ______ replication.
○ a. conservative
● b. semiconservative
○ c. complementary
○ d. dispersive

question 7
if a sequence of one strand of dna is 5-agctgctga-3, what is the complementary strand?
○ a. 5-tcgacgact-3
○ b. 5-agctgctga-3
○ c. 3-tcgacgact-5
○ d. 3-agctgctga-5

Explanation:

• Question 6:
• Conservative replication: The parental double - helix would remain intact, and a completely new double - helix would be formed. But the question states that each new DNA molecule has a parental strand, so A is incorrect.
• Semiconservative replication: Meselson and Stahl's experiment proved that DNA replicates in a semiconservative manner. Each new DNA molecule consists of one parental strand and one newly synthesized strand. This matches the description in the question.
• Complementary: This is a property of base - pairing (A - T, G - C) rather than a replication model. So C is incorrect.
• Dispersive replication: The parental DNA would be fragmented, and the fragments would be incorporated into newly synthesized DNA in a dispersed way. But the question does not mention fragmentation, so D is incorrect.
• Question 7:
• DNA strands are anti - parallel. The 5' end of one strand pairs with the 3' end of the complementary strand.
• For base - pairing: A pairs with T, and G pairs with C.
• Given the strand \(5' - AGCTGCTGA - 3'\), the complementary bases (in the reverse orientation) are \(3' - TCGACGACT - 5'\)

Answer:

• Question 6: B. semiconservative
• Question 7: C. \(3' - TCGACGACT - 5'\)