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

The Shape of the The Shape of the MoleculeMolecule

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

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

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

OneOne Strand of DNAStrand of DNA

• The backbone The backbone of the molecule of the molecule is alternating is 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

NucleotidesNucleotides

C C

C

OPhosphate

O

CC

O -P OO

O

O -P OO

O

O -P OO

O One deoxyribose together with its phosphate and base make

a nucleotide.

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.

• (Adenine and (Adenine and thymine are shown thymine are shown here.)here.)

C

C

CC

N

N

N

N

N

C

C

C

C

C

N

N

OO

OO

C

FourFour nitrogenous basesnitrogenous bases

• 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?

ImportantImportant

• 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

Types of nitrogen bases

• A= adenine• G= guanine• C= cytosine• T= thymine

Do Now!

• Where is DNA located?

• What does it look like?

• What are its bases?• Why do you think

DNA is located there?

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 diameter DNA has a diameter of only 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)

• IF the DNA strand is GTACCAGATTAGC

• What would the RNA strand be?

Transcription

• When a secretary transcribes a speech, the language remains the same. However, the form of the message changes from spoken to written

Transcription

• Transcription- RNA is made from a DNA template in the nucleus.

• This type of RNA is called messenger RNA or mRNA

Transcription

• DNA is protected inside the nucleus.

• mRNA carries the message of DNA into the cytoplasm to the ribosome's

Translation

• To translate English into Chinese requires an interpreter.

• Some person must recognize the worlds of one language and covert them into the other.

tRNA Transfer RNA

• The cells interpreter • tRNA translated the

three-letter codons of mRNA to the amino acids that make up protein.

Translation

• Genetic translation converts nucleic acid language into amino acid language.

Codon

• The flow of information from gene to protein is based on codons.

• A codon is a three-base word that codes for one amino acid

• The flow of information from gene to protein is based on codons.

Information Flow: DNA to RNA to Protein