DNA DNA is the Secret of Life!
Dec 14, 2015
Student goals
The student will• explain the functions of DNA• identify the components of a DNA molecule• summarize the events of DNA replication
DNA
• Functionso1. Storage of genetic informationo2. Self-duplication & inheritanceo3. Expression of the genetic message.oDNA’s major function is to code for
proteins.Information is encoded in the order of the nitrogenous bases.
Discovering the structure of DNA
• Structure was discovered in 1953 by James Watson and Francis Crick
DNA Structure
One 'unit' in the structure of DNA is:
A Phosphate (molecule made with phosphorus)A Sugar (the sugar's name is ribose)A Nitrogen base A- Adenine T-Thymine G-Guanine C-Cytosine
Types of Nucleotides
• A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen.
Adenine (A) Guanine (G) Cytosine (C ) Thymine (T)
The Uprights of the DNA – Phosphate group – Sugar (deoxyribose)
The Rungs of the DNA– Nitrogen Bases(A,G,T,C)
Complimentary BasePairing:– A pairs with T– G pairs with C
DNA is held together by:
Sides - Strong Covalent Bonds
Rungs – WeakHydrogen Bonds
DNA Structure
The middle of the DNA structure is the Nitrogen base of the nucleotide BONDED to the Nitrogen base of the nucleotide on the other side.
A bond with TC bonds with G
This is called complimentary "base pairing"
Important concept
TripletCodon
Amino Acid A
TripletCodon
Amino Acid B
TripletCodon
Amino Acid C
TripletCodon
Amino Acid D
TripletCodon
Amino Acid E
Makes a PROTEIN
HOW IT WORKSDNA CODES FOR PROTEINS TO BE MADE
DNA codes for proteins
• Every 3 nucleotides makes a codon.
• Each codon is the code for an amino acid.
• A chain of amino acids is a protein.
• Your body runs on proteins!
An Analogy for better perspective…
• A Nucleotide (1 sugar, posphate & base) = 1 letter “t”
• 3 nucleotides = a codon = 1 word the• A gene is a long string of codons = 1
paragraph• DNA is a long string of genes = 1 chapter• A chromosome is a VERY long string of DNA
wrapped and bundled with proteins = 1 Book• A genome is all the chromosomes in an
organisme = 1 Entire Library
Quiz Yourself
1. Which one is NOT a function of DNA
A. Stores Genetic information B. Codes for Proteins C. Is the energy of the cell D. Duplicates it's self.
C. DNA is not the energy of the cell.
What is the shape of a DNA molecule?
A. RectangleB. SphereC. Flat ChainD. Double Helix
D. Double Helix
What is true about complimentary base pairs?
A. A bonds with TB. G bonds with AC. C bonds with TD. C bonds with G
A & D