chapter 12.2 dna replication
TRANSCRIPT
12.2 Replication of DNA
Semiconservative Replication Semiconservative Replication- When
the parental strands of DNA separate (serving as templates) and produce DNA molecules that have 1 strand of parental DNA and 1 strand of new DNA
DNA replication occurs during Interphase of Mitosis and Meiosis.
Why it is important Makes duplicate copies of DNA to pass along all
genetic info Without replication, species could not survive During replication, each strand serves as a pattern
to make a new DNA molecule
3 Stages of Semiconservative replication: Unwinding, Base Pairing, and Joining.Step 1: UnwindingAn enzyme (DNA helicase) unwinds and
unzips the double helix. Hydrogen bonds are broken, leaving a leading strand and a lagging strand.
Single-stranded binding proteins keep the strands separated during replication.
RNA primase adds a short segment of RNA (RNA primer) on each strand
Leading strand- moves in the same direction as the replication fork. It replicates continuously. Lagging strand- moves in the opposite direction. It does NOT replicate continuously.
Step 2: Base PairingAn enzyme (DNA polymerase) aids in adding new DNA
nucleotides to the chainSince A binds to T and C binds to G, an identical copy is
made.Okazaki fragments- Short segments of DNA which will later
be connected by DNA ligase. (Lagging strand only)
Step 3: JoiningDNA polymerase comes to a RNA primer
on the DNA, removes the primer, and fills in the place with DNA nucleotides. Once replaced, DNA ligase links (or zips up) the 2 sections.
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/micro04.swf::DNA%20Replication%20Fork
DNA replication animation
The importance of nucleotide sequence
The sequence of nucleotides form the unique genetic information of an organism.
The more closely related two organisms are, the more alike the sequence of nucleotides in the DNA will be.
Ex: Gel Electrophoresis
Gel Electrophoresis