2. POINT > Define nucleotide structure and polarity
POINT > Show how nucleotides link together to form DNA and RNA strands
POINT > Distinguish between DNA and RNA nucleotides
POINT > Define the rules that govern base-pairing in double stranded DNA

3. POINT > Define nucleotide structure and polarity
We describe nucleotides as having three parts: 1. a sugar (ribose or deoxyribose) 2. a nitrogenous base (A, G, C, T or U) 3. a phosphate group
Notice that the carbon atoms on the sugar are numbered 1` to 5`

4. POINT > Distinguish between DNA and RNA nucleotides
DNA sugar RNA sugar

5. What are the three parts of a nucleotide?
WB CHECK:
What are the three parts of a nucleotide?
One difference between DNA and RNA is
a) DNA has phosphates and RNA does not
b) DNA has ribose and RNA has deoxyribose
c) DNA has deoxyribose and RNA has ribose
d) DNA has adenine and RNA has thymine

6. POINT > Distinguish between DNA and RNA nucleotides
DNA strands are made up of adenine, guanine, cytosine, and thymine nucleotides - A G C & T
DNA is double stranded
RNA strands are made up of adenine, guanine, cytosine, and uracil nucleotides - A G C & U
RNA is single stranded

7. POINT > Show how nucleotides can link together to form strands
This is a single strand with 4 nucleotides
Nucleic acids have a “sugar-phosphate backbone”

8. POINT > Show how nucleotides can link together to form strands
The sugar-phosphate backbone is composed of covalent bonds - very strong

9. WB CHECK:
What are the 4 bases in RNA?
What kind of bond holds the sugar phosphate backbone together?
What are the 4 bases in DNA?

10. POINT > Show how nucleotides can link together to form strands
Every DNA or RNA strand has a 5` phosphate (PO4-) at one end and a 3` hydroxyl (OH) at the other end

11. POINT > Show how nucleotides can link together to form strands
Read: ’ A T G C 3’

12. POINT > Define the rules that govern base-pairing in double stranded DNA
An adenine in one strand always bonds with a thymine in the other strand A-T T-A A cytosine in one strand always bonds with a guanine in the other strand C-G G-C

13. POINT > Define the rules that govern base-pairing in double stranded DNA
The bonding of A-T and G-C is called complimentary base-pairing

14. POINT > Define the rules that govern base-pairing in double stranded DNA
The bonds holding A-T and G-C together are hydrogen bonds - relatively weak, but lots of them

15. WB CHECK:
How many nucleotides are in this picture?

16. WB CHECK:
How many base pairs are in this picture?

17. WB CHECK:
How many sugar-phosphate backbones in this picture?

18. WB CHECK:
Give an example of a complimentary base pair:
What kind of bond holds complimentary base pairs together?
Which are stronger, hydrogen bonds or covalent bonds?

19. POINT > Define the rules that govern base-pairing in double stranded DNA
The two strands in a DNA molecule run in opposite 5`-3` directions- they are “anti-parallel”

20. WB CHECK:
If you have a single strand of DNA or RNA with a 3` OH (hydroxyl) at one end, what is at the other end of the strand?
What type of bonds hold the two strands of a DNA molecule to each other?

21. Homework: Read pages 344-348 Assess Page 348 #1-3 Workbook pages 55-56, 203