Chapter 3.3 - DNA Structure Enables DNA Replication ✓ Flashcards
(13 cards)
What does DNA contain that determines the structure and function of living things?
DNA contains genetic code.
What phase of the cell cycle does DNA replication occur?
It occurs during interphase during the S phase
What is the purpose of DNA replication?
The purpose of DNA replication is to produce an identical copy of DNA, ensuring that each daughter cell has the same genetic information during cell division.
Why is DNA replication referred to semi-conservative replication?
It is because one of the two strands is conserved (or retained) from one generation to the next, while the other strand is new.
How does DNA replication start and how?
It starts with an enzyme called helicase unwinding the DNA strand by breaking the weak hydrogen bond between the complementary bases.
Where does helicase start on the DNA strand?
It starts at a certain point called the origin.
What stops the DNA strand from coiling up when unwinding?
single stranded binding proteins (SSBP)
What happens after helicase has unwound the DNA strand?
Another enzyme called RNA primase comes in and makes RNA primers on both strands to show DNA polymerase where to start adding nucleotides
What happens after RNA primase has primed?
DNA polymerase comes in a start building complementary bases on both strands, reading from a 5’ to 3’ strand.
What are the two strands called?
The leading strand is the newly synthesised DNA strand that is built in a 5’ to 3’ direction.
The lagging strand is the newly synthesised DNA strand that is built in a 3’ to 5’ direction.
What happens when DNA polymerase builds complementary bases on the lagging strand?
Since DNA polymerase naturally synthesises DNA in a 5’ to 3’ direction, it builds the leading strand continuously. However, the lagging strand runs in a 3’ to 5’ direction, so DNA polymerase synthesises it in short, discontinuous segments called Okazaki fragments.
What enzyme fills in the gaps between the Okazaki fragments?
DNA ligase
