DNA replication Flashcards
(32 cards)
What happens in the S phase of the cell cycle?
Chromosomes duplicate, and DNA replication occurs.
What is the structure of chromosomes?
Chromosomes are made of DNA and histone proteins.
What is semi-conservative DNA replication?
each new DNA molecule consists of 1 parent strand & 1 new strand.
In which direction does DNA replication occur?
DNA replication always occurs in the 5’ to 3’ direction.
What does the 5’ to 3’ direction mean in DNA replication?
It’s the direction that DNA is built. The 5’ is one end, and the 3’ is the other end where new pieces are added
Why is DNA built in the 5’ to 3’ direction?
DNA can only be built by adding new pieces to the 3’ end of the strand.
How does DNA replication proceed in eukaryotes?
DNA replication has multiple origin sites.
What is the function of helicase in DNA replication?
Helicase unwinds and separates the two DNA strands by breaking hydrogen bonds.
What role do Single-Strand Binding proteins (SSB) play in DNA replication?
SSBs keep the DNA strands separated and untwisted.
What forms at the site where DNA strands separate during replication?
A replication fork forms, which is a Y-shaped region.
What is needed before new DNA strands can form?
RNA primers are needed to start the addition of new nucleotides.
Which enzyme synthesizes the RNA primer?
Primase synthesizes the RNA primer
What does DNA polymerase do?
DNA polymerase adds complementary nucleotides to form the new DNA strand.
What is the difference between the leading strand and the lagging strand?
The leading strand is made smoothly, while the lagging strand is made in small pieces called Okazaki fragments.
How are Okazaki fragments related to DNA replication?
Okazaki fragments are short segments on the lagging strand that are later joined together.
What is the function of SSB proteins during replication?
They prevent the two separated strands from rejoining during DNA replication.
How accurate is DNA replication?
1 in 1 billion.
What is the role of DNA proofreading?
Proofreading enzymes correct base pairing errors during DNA replication.
What happens to the parental strands during DNA replication?
The two strands of the parental molecule separate and each acts as a template for a new complementary strand.
What is excision repair in DNA?
Excision repair removes damaged DNA sections and replaces them with the correct nucleotides.
What are telomeres?
Telomeres are repeating, non-coding sequences at the ends of chromosomes, acting as protective caps.
How do telomeres affect cell division?
Telomeres limit cells to about 50 divisions; they shorten with each division.
What enzyme extends telomeres?
Telomerase extends telomeres by adding DNA bases at the 5′ end.
Where is telomerase activity high?
telomerase is highly active in stem cells and cancer cells.
