1. Structure of DNA (Most slides should be a review you NEED to have the underlined text in notes along with drawings that I say put in notes )

2. DNA is found in the nucleus of a cell.
DNA is wrapped tightly to form chromosomes.
DNA is made up of repeating units called nucleotides.
Nucleotides = sugar & phosphate backbone, & nitrogenous bases pairs (A,T,G,C).

3. DNA Info...... Each cell has about 2 m of DNA
The average human has 75 trillion cells
The average human has enough DNA to go from the earth to the sun more than 400 times
DNA has a diameter of only m

4. Function of DNA…… Storage of genetic information
Self-duplication & inheritance
Expression of the genetic message
DNA’s major function is to code for proteins
Information is encoded in the order of the nitrogenous bases

5. Structure of DNA……
DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix
A molecule of DNA is made up of millions of tiny subunits called Nucleotides
Each Nucleotide consists of:
Phosphate group
Pentose sugar
Nitrogenous base

6. Nucleotides……
Phosphate
Nitrogenous
Base
( A, T, G, C )
Pentose
Sugar

7. The phosphate and sugar form the backbone of the DNA molecule, whereas the nitrogenous bases form the “rungs”
There are four types of nitrogenous bases:
A, T, G, C

8. A
Adenine T
Thymine C
Cytosine G
Guanine

9. Nitrogenous Bases…… Double ring PURINES Adenine (A) Guanine (G)
Single ring PYRIMIDINES
Thymine (T)
Cytosine (C) G A . T C

10. Base Pairing Rules: Purines only pair with Pyrimidines
Hydrogen bonds are extremely weak but the millions of H-bonds together represent an extremely strong force that keeps the two DNA strands together C G
3 H-bonds T A
2 H-bonds

11. Sugar / Phosphate backbone
Nitrogenous Bases P P S S S S S T A P P P
Hydrogen bonds S S S S S S C G P P P P S S S S S S G C P P P P S S S S S S S A T
Nucleotide

12. All the pieces of DNA…… P P S – A ~ T – S P P S – G ~ C – S
S – T ~ A – S
S – C ~ G –S
~ = Hydrogen
bonds
Double helix (twisted ladder)
Backbone = Phosphate (P)
Sugar (S)
Rungs = nitrogenous bases (A,G,T,C)
Purines = Adenine & Guanine
Pyrimidines = Thymine & Cytosine
Base pairing rule =
A – T or T – A
G – C or C - G

14. DNA Replication

15. Cell Division and DNA Replication…
Cells divide for: .
Growth, Repair, Replacement
Before cells divide they have to double cell structures, organelles and their genetic information

16. DNA Replication: A – T and G – C OR T – A and C – G
DNA must be copied before a cell divides
The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:
A – T and G – C OR
T – A and C – G
Each strand of the original DNA serves as a template (or pattern) for the new strand

17. Replication Basics:
DNA is unwound and is unzipped by helicase = enzyme
2 new complementary strands are made; DNA polymerase = enzyme that copies DNA
The original strand is the template for the new strands made

18. 1) Unzipping… Begins at Origins of Replication
Two strands open forming Replication Forks (Y-shaped region)
New strands grow at the forks
Replication
Fork
Parental DNA Molecule 3’ 5’

19. As the 2 DNA strands open at the origin, Replication Bubbles form:

20. More Unzipping…
The enzyme Helicase unzips and separates the 2 DNA strands by breaking the weak hydrogen bonds

21. .
2) DNA Polymerase…
DNA polymerase binds to the strand of the DNA and begins adding nucleotides using the original DNA strand as a template

22. 3) Original → New DNA DNA Template Parental DNA New DNA New DNA
DRAW THIS IN YOUR NOTES
DNA Template
New DNA
Parental DNA
New DNA
DNA Template

23. A ~ T C ~ G T ~ A A T C G T A A ~ T T ~ A
ALSO DRAW THIS IN YOUR NOTES
Unzips
(by helicase)
A ~ T
C ~ G
T ~ A
New Strand
(by DNA polymerase)

25. A C T G G A T
Because of the complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand C

26. DNA → Genetic Code A G G – C T C – A A G – T C C – T A G
To crack the genetic code found in DNA we need to look at the sequence of the nitrogenous bases
The bases are arranged in triplets called codons
Parent Strand
A G G – C T C – A A G – T C C – T A G
T C C – G A G – T T C – A G G – A T C
New Strand codon

27. Gene → trait… A gene is a section of DNA that codes for a protein
Each unique gene has a unique sequence of nitrogenous bases
This unique sequence of bases will code for the production of a unique protein
It is these proteins and combination of proteins that give us our unique traits

28. Gene
Protein
Trait

29. Central Dogma…
DNA
RNA
Amino Acids
Protein
Traits