Biology DNA Structure and Replication Flashcards
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Read the first 7 Biology DNA Structure and Replication flashcards as text
Which enzyme is responsible for unwinding the DNA double helix during replication?
Answer: Helicase
Helicase breaks hydrogen bonds between base pairs to unwind and separate the two DNA strands at the replication fork.
What is the term for the short RNA sequences that initiate DNA synthesis?
Answer: Primers
Primers are short RNA sequences synthesized by primase that provide a free 3'-OH end for DNA polymerase to begin adding nucleotides.
The leading strand is synthesized continuously because it grows in the same direction as:
Answer: The replication fork movement
The leading strand is synthesized continuously in the 5' to 3' direction toward the replication fork, matching its direction of movement.
Which of the following correctly describes the antiparallel nature of DNA?
Answer: One strand runs 5' to 3' while the complementary strand runs 3' to 5'
Antiparallel means the two strands of DNA run in opposite directions: one 5'→3' and its complement 3'→5'.
Chargaff's rules state that in any DNA molecule:
Answer: A + G = C + T
Chargaff's rules state that %A = %T and %G = %C, which means the total purines (A+G) equal total pyrimidines (C+T).
What does the enzyme DNA ligase do during replication?
Answer: Joins Okazaki fragments by forming phosphodiester bonds
DNA ligase seals the nicks between Okazaki fragments on the lagging strand by forming phosphodiester bonds after the RNA primers are replaced with DNA.
Which of the following is NOT a component of a DNA nucleotide?
Answer: Ribose sugar
DNA nucleotides contain deoxyribose (lacking an -OH on the 2' carbon), not ribose, which is found in RNA nucleotides.