1. DNA Deoxyribonucleic acid
Lesson 2
Goal 1: to describe DNA in terms of its structure, location, and function
Goal 2: to compare purine bases and pyrimide bases

2. What is DNA
the nucleic acid that stores and passes on the genetic information from one generation to the next
the source of genetic variation
the source of diversity
Where is DNA?
• DNA is found in the nucleus of cells and does not leave!

3. What is dna composed of?
DNA is composed of units called nucleotides which are composed of three sub-molecules:
1. a 5 carbon sugar (deoxyribose)
2. a phosphate group
3. nitrogenous base (purine or pyrimidine

4. Types of bases PURINES: PYRIMIDINES have 2 rings Have a single ring
Thymine , cytosine, (also Uracil only in RNA)
Memory trick: CUT the Py
PURINES:
have 2 rings
adenine & guanine
Memory trick: 2 rings are pure silver (Ag)

6. Complimentary base pairs
DNA is composed of two complementary strands of nucleotides joined by hydrogen bonds. According to Chargaff’s rules:
Adenine with Thymine (A-T or T-A)
They join with 2 hydrogen bonds
Cytosine with Guanine (C-G or G-C)
They join with 3 hydrogen bonds
Notes: purine always pair with pyrimidine
2 apples in the tree, 3 cars in the garage

7. What does dna look like?
DNA twists into a double helix which resembles a twisted ladder
The backbone (rails of the ladder) are made of alternating
Sugars and phosphate groups
The steps (rungs) are made of the nitrogenous bases.
The two strands are anti-parallel—they run in opposite directions

8. Complete the second strand of DNA
Complete the second strand of DNA. Show the number of bonds between each.
A T G T G A T C C A C G
T A C A C T A G G T G C

9. Functions of the dna
DNA directs the machinery of a cell to make specific proteins and, therefore, DNA indirectly controls all of the functioning of all living things. Protein Synthesis = Cell Control
DNA _stores the hereditary information of an individual
DNA has the ability to mutate (change). This allows for new characteristics and abilities to appear which may help an individual to survive and reproduce (Adaptation – Survival of the Fittest_) Evolution
Self-replication: DNA has the ability to Copy itself DNA Replication & Cell Cycle

10. Cell Division
Protein Synthesis
DNA Replication

11. How do we know
James Watson and Francis Crick 1953—they determined the double helix structure
Rosalind Franklin ( )- chemist and X-ray crystallographer who made contributions to the understanding of the molecular structures of DNA, RNA
Complete the practice, check your answers, then do the quiz on classroom