The “Gurdon” experiment :
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Transcript of The “Gurdon” experiment :
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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.