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Stores and passes on genetic information from one generation to another .
Sugar: deoxyribose
DNA Deoxyribonucleic acid
DNA – Scientists who mapped its structure
Chargaff’s 1949 Observations:
The amount of adenine always equaled the amount of thymine (A = T)
The amount of cytosine always equaled the amount of guanine (C = G)
DNA – Scientists who mapped its structure
Wilkins & Franklin’s Photographs
Using x-ray diffraction, in 1952Developed high-quality photographs of strands of DNA
Suggested that DNA was a tightly coiled helix with 2 or 3 strands of nucleotides
DNA – Scientists who mapped its structure
Watson & Crick’s 3-D DNA model in 1953
“Watson & Crick, took a stick and built the DNA model.”
DNA STRUCTURE
The rungs (steps) of the ladder are pairs of nitrogen bases…
…held together with weak hydrogen bonds.
DNA STRUCTURE
1. ADENINE = A2. GUANINE = G3. CYTOSINE = C4. THYMINE = T
They are represented by their capital letter.
Base Pair Bonding Rules
ADENINE WITH THYMINE(“Stick” Family)
T & A
CYTOSINE WITH GUANINE(“Curve” Family)
C & G
DNA STRUCTURE
ACTCATGGTCATG
TGAGTACCAGTAC
This is an example of a genetic code that may be found in your body.
DNA STRUCTURE
The combinations of the nitrogen bases is the code that produces the genes for a particular trait.
DNA STRUCTURE
Because there can be so many different combinations of the bases, the code can be limitless
DNA Replication
• Replication: to make an identical copy of
Occurs during the “S” phase of the cell cycle.
(Just before mitosis)
DNA Replication
• Also known as:
Semi-Conservative Replication– semi: half–Conserve: to save or reuse–Replicate: to copy exactly
2. Free floating nitrogen bases begin to pair on each strand• Attached by the enzyme DNA
polymerase (the glue)
Semi-conservative Replication
DNA REPLICATION
FYIEach human chromosome is replicated in about 100 sections that are 100,000 nucleotides long.
An entire human chromosome can be replicated in about 8 hours!
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#
DNA Animation
View “DNA Replication Fork”