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

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`

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

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

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

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”

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

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?

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

POINT > Show how nucleotides can link together to form strands Read: 5’ A T G C 3’

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

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

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

WB CHECK: How many nucleotides are in this picture?

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

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

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?

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”

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?

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