Lecture Seven: DNA & Transcription Flashcards
(Step One: Strand separation) When the helicase binds to a replication origin, what begins to happen?
it begins to unwind the two strands of DNA by breaking the hydrogen bonds between complementary base pairs
(Step One: Strand separation) As the strands separate, what happens next?
they form a y-shaped structure (the replication fork)
(Step One: Strand separation) A class of enzymes is called?
Topoisomerases
(Step One: Strand separation) what do Topoisomerase help relieve? and how do they do this?
The tension in the DNA strands, they do this by cutting one or two of the strands near the replication fork
(Step One: Strand separation) What happens after the strands are separated?
the strands want to rejoin (b/c they are complementary)
(Step One: Strand separation) What prevents the strands from re-joining?
Single-strand binding proteins prevent this by attaching to the DNA strands to stabilize them and keep them separated
(Step One: Strand separation) What is added soon after the separation?
new complementary nucleotides are added to the naked strand
(Step One: Strand separation) How are the two identical daughter strands formed?
They are formed by the separation in DNA (in both directions) which forms replication bubbles. the bubbles will then expand along the length of the molecule until they meet/merge with another bubble, creating separation
(Step Two: building complementary strands) what do DNA polymerase add?
they add nucleotides to the 3’ end of a new developing strand while moving along and reading the template strand 3’ to 5’ direction
(Step Two: building complementary strands) What can polymerase add?
They can only add nucleotides to the 3’ end of the existing DNA
(Step Two: building complementary strands) How is the new strand assembled?
5’-3’ direction
(Step Two: building complementary strands) What does the DNA polymerase use to build a new strand of the DNA?
Nucleoside triphosphate
(Step Two: building complementary strands) What is required to build a new strand?
energy
(Step Two: building complementary strands) How is the energy required?
comes from the phosphate groups attached to the nucleolus molecule
(Step Two: building complementary strands) What is produced?
2 phosphates
