DNADNA DNA is often

called the blueprint of life.

In simple terms, DNA contains the instructions for making proteins within the cell.

Why do we study Why do we study DNADNA??We study DNA for We study DNA for

many reasons:many reasons: its central its central

importance to importance to all life on Earthall life on Earth

medical benefits medical benefits such as cures such as cures for diseasesfor diseases

better food better food crops.crops.

Chromosomes and Chromosomes and DNADNA

Chromosomes Chromosomes are made up of are made up of genes.genes.

Genes are Genes are made up of a made up of a chemical called chemical called DNA.DNA.

The Shape of the The Shape of the MoleculeMolecule

DNA is a very DNA is a very long molecule.long molecule.

The basic shape The basic shape is like a twisted is like a twisted ladder or zipper.ladder or zipper.

This is called a This is called a double helix.double helix.

OneOne Strand of DNAStrand of DNA

The backbone of The backbone of the molecule is the molecule is alternating alternating phosphatephosphate and and deoxyribosedeoxyribose, a , a sugar, parts.sugar, parts.

The teeth are The teeth are nitrogenousnitrogenous basesbases..

phosphate

deoxyribose

bases

The Double Helix The Double Helix MoleculeMolecule

The DNA double The DNA double helix has two helix has two strands twisted strands twisted together.together.

(In the rest of (In the rest of this unit we will this unit we will look at the look at the structure of one structure of one strand.)strand.)

The Nucleus

DNA is located in the nucleus

DNAdeoxyribonucleic acid

The code of life

One deoxyribose together with its phosphate and base make

a nucleotide.

C C

C

OPhosphate

O

CC

O -P OO

O

O -P OO

O

O -P OO

O

Nitrogenous base

Deoxyribose

The Basics

Each side of the ladder is made up of nucleic acids.

The backbone is a phosphate and a sugar

The rung of the ladder is the nitrogen base.

Hydrogen BondsHydrogen Bonds When making When making

hydrogen bonds, hydrogen bonds, cytosine always cytosine always pairs up with pairs up with guanine, guanine,

And adenine And adenine always pairs up always pairs up with thymine.with thymine.

C

C

CC

N

N

N

N

N

C

C

C

C

C

N

N

OO

OO

C

FourFour nitrogenous nitrogenous basesbases

Cytosine Cytosine C C Thymine Thymine TT

Adenine Adenine AA Guanine Guanine GG

DNA has four different bases:DNA has four different bases:

Two Stranded DNATwo Stranded DNA Remember, DNA Remember, DNA

has two strands has two strands that fit together that fit together something like a something like a zipper.zipper.

The teeth are The teeth are the nitrogenous the nitrogenous bases but why bases but why do they stick do they stick together?together?

• Adenine and Adenine and Thymine always join Thymine always join

togethertogether

A -- TA -- T• Cytosine and Cytosine and

Guanine always join Guanine always join togethertogether

C -- GC -- G

Copying DNA Step 1- DNA unwinds and

unzips Step 2- Once the molecule

is separated it copies itself. The new strand of DNA has

bases identical to the original

DNA by the DNA by the numbersnumbers Each cell has about Each cell has about

2 m of DNA.2 m of DNA. The average human The average human

has 75 trillion cells.has 75 trillion cells. The average human The average human

has enough DNA to has enough DNA to go from the earth go from the earth to the sun more to the sun more than 400 times.than 400 times.

DNA has a DNA has a diameter of only diameter of only 0.000000002 m.0.000000002 m.

The earth is 150 billion mThe earth is 150 billion mor 93 million miles from or 93 million miles from the sun.the sun.

What’s the main difference between DNA and RNA

RNA In RNA Thymine is

replaced by Uracil A-U (RNA) not A-T (DNA)

Quiz Time

IF the DNA strand is GTACCAGATTAGC

What would the RNA strand be?