Genetics and Society

PowerPoint revised from: hum.utah.edu/~bbenham/251

0%20Spring%2008/class%203%20central%20dogma.ppt

OutlineWhat is a gene?

Central dogmaReplication (DNA makes DNA)Transcription (DNA makes RNA)Translation (RNA makes Protein)

5' 3'

“Watson”

“Crick”

5' 3'

?

http://giant-panda.com/

5' 3'

“Watson”

“Crick”

5' 3'

genes

http://giant-panda.com/

What is a gene?

http://cmgm.stanford.edu/biochem201/Slides/Chromatin%20Structure/01%20Human%20Chromosome.JPG

A gene is a section of DNA(usually several 10,000’s of base pairs long)

A gene is a section of DNA

chromosome gene

What is a gene?

http://cmgm.stanford.edu/biochem201/Slides/Chromatin%20Structure/01%20Human%20Chromosome.JPG

A gene is a section of DNA(usually several 10,000’s of base pairs long)

A gene makes a protein.

Proteins do things

EnzymesEnzymes are a type of protein (or RNA molecule) that speed up metabolic reactions in plants and animals.

They are not permanently changed or destroyed when they do so.

A gene “makes” a protein.

How?

The Central Dogma

The Central DogmaI called this idea the central dogma, for two reasons, I suspect. I had already used the obvious word hypothesis in the sequence hypothesis, and in addition I wanted to suggest that this new assumption was more central and more powerful. ... As it turned out, the use of the word dogma caused almost more trouble than it was worth.... Many years later Jacques Monod pointed out to me that I did not appear to understand the correct use of the word dogma, which is a belief that cannot be doubted. I did apprehend this in a vague sort of way but since I thought that all religious beliefs were without foundation, I used the word the way I myself thought about it, not as most of the world does, and simply applied it to a grand hypothesis that, however plausible, had little direct experimental support.

-Francis Crick

Complementarity is the secret of life

A T

G C

Central Dogma:

DNA

RNA

Protein

Complementarity

Central Dogma

DNA

RNA

Protein

Replication

DNA is the long-term storage medium

DNA is copied when cells divide

"It has not escaped our notice that the specific pairing that we have postulated immediately suggests a possible copying mechanism for the genetic material"

Complementarity allows DNA to be copied exactly

Replication

AGC TAG C A C TAC T GA A G T G C G C CTCG ATC G T G ATG A CT T C A C G C G G

AGC TAG C A C TAC T GA A G T G C G C C

TCG ATC G T G ATG A CT T C A C G C G G

TCG ATC G T G ATG A CT T C A C G C G G

AGC TAG C A C TAC T GA A G T G C G C C

Central Dogma

DNA

RNA

Protein

Replication

Transcription

RNA is a temporary copy of the DNA information

DNA RNA

RNA is copied from 1 DNA strand

TranscriptionAGC TAG C A C TAC T GA A G T G C G C CTCG ATC G T G ATG A CT T C A C G C G G

AGC TAG C A C TAC T GA A G T G C G C C

TCG ATC G T G ATG A CT T C A C G C G G

DNA

AGC UAG C A C UAC U GA A G U G C G C C RNA

(Complementarity again)

RNA is copied from 1 DNA strand

TranscriptionAGC TAG C A C TAC T GA A G T G C G C CTCG ATC G T G ATG A CT T C A C G C G G

AGC TAG C A C TAC T GA A G T G C G C CTCG ATC G T G ATG A CT T C A C G C G G

DNA

AGC UAG C A C UAC U GA A G U G C G C C RNA

(mRNA- messenger)

RNA vs. DNA

http://www.mun.ca/biology/scarr/Ribose_sugar.html

RNA uses U in place of T

About 1/10,000,000 C bases decompose to U per day.

Because DNA uses T, not U, the cell automatically assumes that U is the result of a C gone bad and removes all U bases from DNA.

C U T

Central Dogma

DNA

RNA

Protein

Replication

Transcription

Translation

Protein is the final product of the information

mRNA ProteinTranslation

Proteins are made of 20 different amino acids

Amino acids can be linked together

Proteins are long chains of amino acids

Protein(a real protein would have hundreds of amino acids)

Proteins are long chains of amino acids

Hemoglobin

Protein chains fold into complex shapes that depend on the sequence of amino acids

Protein

An RNA “adapter” is used to convert RNA to Protein

U A C

tRNA

Amino Acid

Complementarity is used to convert the information in RNA

into protein

mRNAUCU AUC G U G AUA C CU U C A C G C

Amino Acids

tRNAAGA UAG C A C UAU G GA A G U G C G U G A

Complementarity is used to convert the information in RNA

into protein

U A CCU U

UCC

UC GAU U G A A

C G C

Protein

mRNAAGA UAG C A C UAU G GA A G U G C G U G A

AUG is the translation startUAA UAG or UGA are stop

U A CCU U

UCC

UC GAU U G A A

C G C

Protein

mRNAAGA UAG C A C UAU G GA A G U G C G U G A

START STOP

Where do these events occur in the cell?

Replication

Transcription TranslationmRNA mRNA

Protein

Nucleus

Not all of the DNA gets copied into RNA

DNA

A gene is a piece of DNA that

makes a protein

RNA

Not all of the DNA gets copied into RNA

DNA

RNA

•Some of the DNA encodes when, where and how much of the RNA to make. This is called the promoter.

promoter

A gene is a piece of DNA that

makes a protein

Different cells copy different parts of the DNA into RNA

Hemoglobin

Insulin

Different cells copy different parts of the DNA into RNA

Hemoglobin

Insulin

Blood cell

mRNA hemoglobin

Different cells copy different parts of the DNA into RNA

Hemoglobin

Insulin

Pancreas cell

mRNA insulin

Genes in some well known organisms

<10 m12 M base pairs6,300 genes

~1 mm97 M base pairs19,100 genes

http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize

http://elegans.swmed.edu/http://www.genomenewsnetwork.org/articles/12_03/yeast_screen.shtml

Genes in some well known organisms

~1 cm180 M base pairs13,600 genes

~10 cm 125 M base pairs 25,500 genes

http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize

http://www.rhone-alpes-genopole.com/index.php?pageID=52&tabNum=2http://www.cofc.edu/~bernardoj/Genetics%20Lab/212Lhome.htm

Genes in some well known organisms

2,500 M base pairs~30,00 genes

2,900 M (~3 billion) base pairs~30,000 genes

http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize

http://www.bcgsc.ca/gc/mouse/http://www.thatsweird.net/picture32.shtml

The exact types and amounts of protein made by our DNA

make us what we are.

5' 3'

“Watson”

“Crick”

5' 3'

http://giant-panda.com/

DNA

RNA

Protein

Identical twins share the same DNA

Lech and Jaroslaw Kaczynski, president and prime minister of Poland

http://english.pravda.ru/news/world/10-07-2006/83163-poland-0

Genes provide possibilities

•Hemoglobin genes make it possible to have normal blood

•A large number of genes make it possible to have a properly wired brain.

Genes provide possibilities

Can you name other examples of things that are possible or not possible because of genes?

Genes provide probabilities

•A particular set of genes will make it probable that someone will be tall.

•DNA repair genes make it probable that a person will not get cancer.

Environment will affect the odds

Genes provide probabilities

Can you name other traits that are affected by both genes and the environment?

Genes for…

Right:

A gene for hemoglobinA gene for insulin

Wrong:

A gene for mathA gene for alcoholismA gene for loyalty

Genes affect traits, but still a gene makes a protein, not a trait

What is a gene?

What is the central dogma?

What is the central dogma?

How does complementarity fit into the central dogma?

DNA

RNA

Protein

A T

G C

Postscript: Central Dogma Exceptions

DNA

RNA

Protein

RNA viruses (RNA > Protein, no DNA)Retroviruses (RNA > DNA)Prions (Protein > Protein)Catalytic RNA (DNA > RNA, no Protein)RNAi (RNA > RNA, no DNA or Protein)