R

r

R

rR

r

R

rR

r

R

rR

r

The “Gurdon” experiment:

Does every cell in an organismcontain all the genetic informationto make a complete individual?

Unfertilizedegg

Ultravioletradiationof egg todestroynucleus

Enucleatedegg

Host egg

Host egg Donor nucleus

Host egg Donor nucleus

How is genetic information copied every time a cell divides?

The two strands separate andeach strand is used as atemplate for the synthesis of a new strand.

How is genetic information copied every time a cell divides?

DNA polymerase is the enzyme(protein) that carries out DNAreplication.

Bacteria have about 5 million basepairs of DNA.

Bacteria can divide every 20 minutes.

DNA polymerase replicates bacterial DNAat a rate of 4200 basepairs/second.

What is a gene?

Genes are the basic units of inheritance.

Genes are information to make proteins.

one gene one protein

Most higher organisms have 15,000 - 35,000 different genes

These organisms have the information(DNA) to make 15,000 - 35,000

different proteins

How is genetic information stored in DNA?

As a sequence of bases(ATGCATTCGCAATT…)

the sequence of aminoacids in a protein.

the 3-D shape of the protein.

the function of the protein.

The sequence of bases in DNAdetermines

The sequence of amino acids in aprotein determines

The 3-D shape of the protein determines

Hemoglobin

DNA Polymerase

DNA cutting enzyme

Receptor protein

Genes are arranged on chromosomes like beads on a string

Gene 1 Gene 2 Gene 3 Gene 4 Gene 5

DNA

A typical chromosome has thousands of genes

Humans have 23 pairs of chromosomes (46 total)

Fruit Flies have 4 pairs of chromosomes (8 total)

Arabidopsis has 5 pairs of chromosomes (10 total)

Gene 1 Gene 2 Gene 3 Gene 4 Gene 5

Chromosome

Genes code for proteins

Gene 1 Gene 2 Gene 3 Gene 4 Gene 5

chromosome

Protein 1 Protein 2 Protein 3 Protein 4 Protein 5

Central Dogma of Biology

DNA

RNA

cytoplasmnucleus

Transcription: DNA RNA

DNA

RNA

RNA

cytoplasm

RNA is transported to cytoplasm

nucleus

DNA

protein

RNA

cytoplasm

Translation: RNA protein

nucleus

DNA

RNA

protein

RNA

cytoplasm

DNA RNA protein

nucleus

Properties of DNA

• Double stranded

• Deoxyribonucleic acid

• Bases: A, G, C and T

Properties of RNA

• Single stranded

• Ribonucleic acid

• Bases: A, G, C and U (U = uracil)

… GGC TGT GGC TAG… CCG ACA CCG ATC

… GGC UGU GGC UAG

DNA(bases)

RNA(bases)

Central Dogma of BiologyDNA RNA protein

transcription transcription

The code in RNA is read three bases ata time

translationtranscription

… GGC TGT GGC TAG… CCG ACA CCG ATC

… GGC UGU GGC UAG

… Gly

DNA(bases)

RNA(bases)

Protein(amino acids)

Central Dogma of BiologyDNA RNA protein

transcription transcription

translation translation

… GGC TGT GGC TAG… CCG ACA CCG ATC

… GGC UGU GGC UAG

… Gly - Cys

DNA(bases)

RNA(bases)

Protein(amino acids)

Central Dogma of BiologyDNA RNA protein

transcription transcription

translation translation

… GGC TGT GGC TAG… CCG ACA CCG ATC

… GGC UGU GGC UAG

… Gly - Cys - Gly

DNA(bases)

RNA(bases)

Protein(amino acids)

Central Dogma of BiologyDNA RNA protein

transcription transcription

translation translation

… GGC TGT GGC TAG… CCG ACA CCG ATC

… GGC UGU GGC UAG

… Gly - Cys - Gly Stop

DNA(bases)

RNA(bases)

Protein(amino acids)

Central Dogma of BiologyDNA RNA protein

transcription transcription

translation translation

The Genetic Code is Universal

AUG codes for the amino acid methioninein all organisms (bacteria, fungi, plants,and animals)

GGC codes for the amino acid glycinein all organisms (bacteria, fungi, plants,and animals)

The Genetic Code is Universal

This fact proves one of Darwin’s most remarkable predictions:

All life forms evolved from a common ancestor.

What is a mutation?

A mutation is a change in the basesequence in DNA that results in achange in the amino acid sequenceof a protein.

… GGC TGT GGC TAG… CCG ACA CCG ATC

DNA

… GGC TAT GGC TAG… CCG ATA CCG ATC

normal mutant

RNA … GGC UAU GGC UAG

transcription

… GGC UGU GGC UAG

transcription

… Gly - … Gly -Protein

translation translation

Cys - Gly Stop Tyr - Gly Stop

ON

OFF

regulatoryregion

(on/off switch)

coding region(codes for amino acids)

A gene is composed of two parts:

Transcription factors turn genes on and off.

Transcription factors are proteins that bind to a specific base sequence in DNA.

…AGCCTACCAAAAAAGGTTCCACG……TCGGATGGTTTTTTCCAAGGTGC…

regulatoryregion

(on/off switch)

coding region(codes for amino acids)

- Some transcription factors are activators:They turn genes ON.

regulatoryregion

(on/off switch)

coding region(codes for amino acids)

- Some transcription factors are activators:They turn genes ON.

- Some transcription factors are repressors:They turn genes OFF.