DNA

DNA is the Secret of Life!

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 and Function

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

Adenine + ThymineDouble H+ Bond

Guanine + CytosineTriple H+ Bonds

Complementary Base Pairing

Discovering the structure of DNA

Rosalind Franklin’s DNA image

“Chargoff’s rule”A = T & C = G

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.

C, A, T and G are

A.  SugarsB.  Nitrogen BasesC.  PhosphatesD. Proteins

B.  Nitrogen Bases

How many nucleotides in a codon?

a.  1b.  3c.  6d.  Nucleotides don't make up a codon.

B.  3

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

If a strand of DNA  readAATGCC

What would the complementary strand read?

A. CCGATTB.TTAGATC.TTACGGD.CCATGG

B.TTAGAT