Download Replication PP

Do Now 3/7
• OBJECTIVES:
– 1. Describe the structure of DNA.
– 2. Describe DNA replication, and be able to determine
the sequence of a complementary strand using basepairing rules.
• TASK:
1. HW check -
The Race to Discover DNA’s Structure
Maurice Wilkins
X-Ray diffraction image of DNA taken by
Franklin in 1951
Rosalind Franklin
James
&
The Race
toWATSON
Discover
DNA’s
Francis CRICK
Structure
Awarded
Nobel
Prize for DNA’s
Structure
1953
Compiled data from
previous scientists
to build a doublehelical model of
DNA
James Watson
Francis Crick
The Race to Discover DNA’s Structure
was Over
• DNA is made up of:
– Four nucleotides: Adenine, Thymine, Guanine
and Cytosine
– These follow the rules of base-pairing:
• Adenine bonds with Thymine
• Guanine bonds with Cytosine
– A sugar-phosphate backbone
• DNA is arranged in a double-helix
Complimentary Strands
• Complementary Sequences: Two strands of
nucleotides that stick together because they have
“opposite” sequences that form “base pairs”.
• (A-T; G-C)
Hey, nice
sequence!
Thanks! You
too!
DNA Replication
• The double helix did explain
how DNA copies itself
• We will study this process,
DNA replication, in more
detail
DNA Replication is Semi-Conservative
Each old strand provides the information to build a
new strand.
DNA Replication
The “parent” molecule has two complementary strands of DNA.
Each is base paired by hydrogen bonding with its specific partner:
A with T
G with C
DNA Replication
The first step in replication is the separation of the two strands.
DNA Replication
Each parental strand now serves as a template that determines the order of the
bases along a new complementary strand.
DNA Replication
The nucleotides are connected to form the sugar-phosphate backbones of the new
strands.
Each “daughter” DNA molecule consists of one
parental strand and one new strand.
Replication Enzymes
• DNA replication involves many enzymes.
• DNA Polymerase: Builds new strands of DNA from
nucleotides by using old strand sequence
KEY IDEAS
• DNA base-pairing rules:
A=T and G=C because of shape & charge
• DNA structure:
– Double helix with bases on the INSIDE. Sugar & Phosphate OUTSIDE
• DNA replication is semi-conservative
Each new molecule made has 1 old and 1 new strand
Replication Activity
• You will now model the process of DNA
replication with your team.
• Follow the step-by-step guide and you can’t go
wrong.