DNA Replication

Replication Process by which DNA makes an exact copy of itself Results in 2 identical DNA molecules

Discussion Question Turn to someone next to you and come up with an answer to the following question. Why would an organism want two identical molecules of DNA?

Why replication?? Allow new cells to have exactly the same genetic info as old cells This is how traits are passed on Can be used to make new cells

Sites of Replication DNA Replication starts at the Origin of Replication There can be many origins of replication along same DNA strand Speeds up the process

How does replication work? Step 1:An enzyme called DNA helicase unwinds the DNA by breaking the hydrogen bonds between the nitrogen bases Forms a replication fork

How Replication Works Step 2: Single Stranded Binding Proteins keep the DNA strands apart

How Replication Works Step 3: RNA Primase adds a short strand of complimentary nucleotides at the Origin of Replication

How Replication Works Step 4: DNA polymerase matches up complementary DNA nucleotides with the nucleotides on the old DNA strand continuously in a 5’ to 3’ direction. This is called the leading strand

How Replication Works Step 5: The other DNA strand, the lagging strand, still has nucleotides added to it by DNA polymerase, but they have to add in short strands called Okazaki fragments since the lagging strand goes in the 3’ to 5’ direction

How Replication Works Step 6: DNA ligase connects the Okazaki fragments together

How Replication Works Step 7: DNA polymerase then bonds the sugar and the phosphate from each nucleotide together forming a complete strand of DNA

How Replication Works Results: Each new DNA strand contains ½ of the original strand and ½ new nucleotides This is known as semiconservative because each strand has half the old strand.

Crash Course Video https://www.youtube.com/watch?v=8kK2zwjRV0M