DNA replication

Question 1

What does semi conservative mean?

Answer 1

Two parental strands separate and each serves as a template for a new progeny strand
(Half the strand is saved)
(Meselson and stahl)

Question 2

What are the 3 stages of DNA replication?

Answer 2

Initiation
Elongation
Quality control

Question 3

Initiation

Answer 3

HELICASE enzyme breaks hydrogen bonds b/w base pairs- unzips strand

SSB’s bind to exposed strands, preventing them from re joining (annealing)

REPLICATION FORKS (where DNA is still joined and enzymes are bound) increase speed of replication, replicating bubbles form and meet creating 2 daughter DNA molecules

PRIMING
DNA POLYMERASE 3 adds complimentary nucleotides in the 5’ to 3’ direction using RNA PRIMERS as a starting point … PRIMASE is the enzyme requires to add RNA PRIMERS

Question 4

Elongation

Answer 4

Direction of replication occurs in 5’ to 3’ direction

BIDIRECTIONAL- replication occurs toward fork in one strand and away from fork on the other

LEADING STRAND- is built continuously toward fork in 5’ to 3’ direction

LAGGING STRAND- is discontinuously, in short OKAZAKI FRAGMENTS away from fork

DNA POLYMERASE 1 removes RNA PRIMERS and replaces w/ correct nucleotide

DNA LIGASE (glue) joins OKAZAKI FRAGMENTS together by making a PHOSPHODIESTER BOND

Question 5

Quality control

Answer 5

DNA POLYMERASE 1&3 are proof readers of new daughter DNA
When they encounter a mistake- act as EXONUCLEASE (scissors) and cut out the wrong nucleotide and replace it

This process happens immediately to prevent repeating the error again

Question 6

What is DNA replication?

Answer 6

The process by which DNA makes a copy of itself