DNA Structure and Function
What are the four nitrogenous bases in DNA, and how do they pair?
A pairs with T and G pairs with C
What enzyme unwinds the DNA double helix at the start of replication?
Helicase
Who are the two scientists credited with discovering the structure of DNA?
James Watson and Francis Crick
What enzyme proofreads newly synthesized DNA for errors?
DNA polymerase
Where does DNA replication occur in eukaryotic cells?
Nucleus
What type of bond holds the nitrogenous bases together in the DNA double helix?
Hydrogen bonds
What is the name of the enzyme that synthesizes the new DNA strand by adding nucleotides?
DNA polymerase
What experiment by Avery, MacLeod, and McCarty proved that DNA, not proteins, was the hereditary material?
The transformation experiment with pneumococcal bacteria.
What is a mutation?
A change in the DNA sequence.
During what phase of the cell cycle does DNA replication occur?
S phase (Synthesis phase)
What is the term for the structure of DNA that allows it to store genetic information and be copied?
A double helix
What is the purpose of RNA primers in DNA replication?
They provide a starting point for DNA polymerase to begin replication.
What was the key piece of evidence (photo) that helped Watson and Crick determine DNA's structure?
Photo 51
How does DNA polymerase ensure accuracy during DNA replication?
It has a proofreading function that detects and corrects mismatched nucleotides.
What is the function of topoisomerase in DNA replication?
It prevents the DNA from becoming too tightly coiled by cutting and rejoining strands.
Who used X-ray crystallography to determine the helical structure of DNA?
Rosalind Franklin
Why does DNA replication have a leading and lagging strand?
DNA polymerase can only add nucleotides in the 5' to 3' direction, causing discontinuous replication on the lagging strand.
What rule states that the amount of A in DNA always equals the amount of T, and the amount of G always equals the amount of C?
Chargaff's rule
What happens if an error in DNA replication is not corrected?
It can become a permanent change in the DNA sequence, which may affect protein production.
What is the term for the point where DNA replication begins?
Origin of replication
Why is DNA considered antiparallel?
The two strands run in opposite directions, with one strand in a 5' to 3' direction and the other in a 3' to 5' direction.
What are the short fragments called that are synthesized on the lagging strand?
Okazaki fragments
What was the key conclusion from the Hershey-Chase experiment?
What is the role of mismatch repair enzymes in DNA replication?
They detect and correct errors that escape DNA polymerase’s proofreading process.
What is the difference between prokaryotic and eukaryotic DNA replication?
Prokaryotic replication occurs at a single origin, while eukaryotic replication occurs at multiple origins.