1. DNA

2. Biomolecules – Remember
Carbohydrates
Lipids
Nucleic acids – hold genetic information; code for proteins
Proteins

3. History of DNA

4. Who Discovered DNA Rosalind Franklin James Watson & Francis Crick
Took X-ray diffraction images
In 1953
James Watson & Francis Crick
Used Franklin’s image
Developed the 1st accurate model of DNA

5. Overall Importance to Organisms
Nucleic Acids
Overall Importance to Organisms
Stores and transmits genetic hereditary information
Codes for proteins
Gene- specific segment of DNA

6. Nucleic Acids DNA – double stranded genetic molecule RNA – single stranded genetic molecule

7. Basic Building Block- Nucleotide

8. Sugar part of Nucleic Acids
DNA
RNA

9. Base pairs in DNA: A – T and G – C
Hydrogen bonds

10. Held together by H bonds

11. DNA Double Helix – “ Twisted Ladder”
“Rungs” of ladder are Nitrogenous base pairs held together by weak Hydrogen bonds
Adenine with Thymine
Guanine with Cytosine
Side of ladder
Alternating Sugar and phosphate backbone

12. Antiparallel Strands Parallel Strands5’ 5’ 3’ 5’ 3’ 3’ 5’ 3’
Antiparallel Strands
Parallel Strands

13. Nucleosome

14. DNA  histones nucleosomes chromosomes Organization of DNA
In chromosomes, DNA is wound around histones A nucleosomes is a cluster of 8 histones

15. Reason for Packaging
DNA must be tightly wound in order to fit inside the nucleus or nucleoid region of a cell
Uncoiled human DNA is about 6 feet long!

16. Summary of DNA Structure
DNA is made of nucleotides as building blocks
Nucleotides consist of deoxyribose (sugar), phosphate and a base
DNA has a antiparallel double helix shape
DNA is held together by hydrogen bonds
DNA consists of two strands joined by complementary base pairs
Adenine and Thymine (A-T)
Guanine and Cytosine (G-C)
A segment of DNA is called a gene, which codes for proteins

17. DNA Replication

18. Replication Replication – copying DNA for new daughter cell
Occurs during S phase of cell cycle
S for DNA Synthesis

19. Replication – copying DNA
Replication – copying DNA to supply new cells with DNA copy DNA – instructions to make proteins and specialized cells

20. Base sequence
The sequence of bases codes for proteins Ex. The strand you see now is ACAGGACGAC which may be the gene for the protein, keratin, in your fingernails That sequence of DNA would be the gene for keratin

21. Human DNA (As Chromosomes) 23 pairs of chromosomes 25, 000 genes

22. Growth – increase # of cells
Replication is used to provide new cells with copy of DNA when new cells divide for
Healing
Replacement
Growth – increase # of cells

23. Cancer – uncontrollable growth of cells Defect in their DNA that tells them to keep growing and dividing

24. Cancer Cells under Microscope

25. DNA Replication – What do you see?

26. Terms of Replication Helicase – enzyme that unwinds DNA
DNA Polymerase – enzyme that adds nucleotides to DNA
Parent strand – original DNA double helix
Daughter DNA –DNA copies with one side from parent strand and one new side
Replication fork – where DNA is unwound and separated into 2 single strands

27. Steps of DNA Replication – S phase
Helicase carefully unwinds double helix of DNA, revealing replication fork
DNA Polymerase adds complimentary nucleotides to the two original strands of unwound DNA
Hydrogen bonds hold Adenine to Thymine, and Cytosine to Guanine
Two new strands of DNA are formed, one for original cell, and one for new cell

28. Can you label the parts?

29. Helpful Videos
eplication1.swf
Flash –DNA Replication
3D animation mechanism-of-replication-advanced.html
Overview of DNA structure and replication

30. Mutations
Actual Mutations
in fruit flies

31. What Causes Mutations? Environment: a physical or chemical cause.
Examples: UV light, radiation, drugs, and benzene.
Mutagens are often also carcinogens – anything that causes cancer
Can be natural, random events.
- mutations occur in 1/100,000 DNA replications (DNA mistakes)
Mutations do not have to be bad (evolution)

32. Mutations Mistakes made during replication
If a mutation occurs in a sex cell, the mutation will be passed to offspring
Examples: Down Syndrome
A mutation is any change in a cell’s DNA
Types of Mutations
Point Mutations
Substitutions
Frame Shift (insertion and deletion)

33. Mutations on Chromosomes