30431
Introduktion til Bioinormatik
Introduction
to Bioinformatics
DNA
Structures and Information
David
Ussery
8
September, 1998
Gene Expression
& Regulation
Brief Outline
1. DNA
is the Genetic Material
2.
The flow of Genetic Information
3.
Synthesizing Proteins from the Instructions of DNA
4.
The Genetic Code
5.
RNA: Intermediary in Protein Synthesis
6.
Protein Synthesis
7.
Mutations in DNA and Their Effects
8.
Gene Regulation
1.
DNA is the gentic material
The First demonstration of bacterial transformation.
Experiments done by Frederick Griffith (in London) in 1928 found there
were two different types of the bacterium Streptococcus pneumoniae:
An "S" or SMOOTH coat strain, which is lethal to mice.
An "R" or rough strain, which will not hurt the mouse.
Griffith found that he could heat inactivate the smooth strain.
However, if he were to take a mixture of the heat-inactivated S
strain,
mixed with the R strain, the bacteria would die. Thus there
was some
Material in the heat-killed S strain that was responsible for "transforming"
the R strain into a lethal form.
Fred Griffith (and a lab co-worker) was killed in their laboratory in 1940
from a German bomb. However, their work continued on in the U.S.,
and in 1944, Oswald Avery, C.M. MacLeod, and M. McCarty carefully demonstrated
that the ONLY material that was responsible for the transformation was
DNA - thus, DNA was the "Genetic material" - however, many scientists were
still not sure that it was REALLY DNA (and not proteins) that was the genetic
material.
In 1952, Alfred Hershey and Martha Chase (she was an UNDERGRADUATE at
the time!) demonstrated clearly that DNA must be the genetic material,
using bacteriophage T2.
2.
The flow of Genetic Information:
DNA
->
RNA ->
protein
This is known as:
The Central
Dogma of Molecular Biology
The Relationship
between Genes and Proteins
-
Most genes encode
the information for the synthesis of a protein
-
The sequence of
bases in DNA codes for the sequence of amino acids in proteins
Shown below is an Illustration
of the transcription of DNA to RNA to protein which forms the backbone
of molecular biology.
LEGEND
-
DNA codes for the production
of RNA.
-
RNA codes for the production
of protein.
-
Protein does not code for
the production of protein, RNA or DNA.
-
The end.
Or in the words of Francis
Crick:
Once
information has passed into protein, it cannot get out again.
This was taken from Genetech's homepage:
However,
the "Central Dogma" has had to be revised a bit. It turns out that
you CAN go back from RNA to DNA, and that RNA can also make copies of itself.
It is still not possible to go from Proteins back to RNA or DNA, and no
known mechanism has yet been demonstrated for proteins making copies of
themselves.
Try it for youself on the "DNA
Workshop" (from PBS).
Click
HERE for a link to nice historical review of The Central Dogma.
3.
Synthesizing Proteins from the Instructions of DNA
-
Genetic information flows in a
cell from:
-
DNA
->RNA->
Protein
-
-
-
4.
The Genetic Code
-
-
The Genetic Code uses three bases
to specify each amino acid
5.
RNA: Intermediary in Protein Synthesis
-
Transcription produces RNA molecules
that are complimentary copies of one strand of DNA
-
Three types of RNA cooperate in
protein synthesis
6.
Protein Synthesis
Click "Reload" to see the animation
Proteins are made from the "N" (amino) side to the "C" terminus (carboxyl
end).
7.
Mutations in DNA and Their Effects
-
Point mutations are changes in
a single base
-
Insertion and deletion mutations
result from addition or removal of nucleotides
-
Mutations differ in their effects
on protein structure and function
-
Mutations provide the raw material
for evolution
-
8a.
Gene Regulation in Prokaryotes (bacteria)
-
-
-
8b. Gene Regulation
in Eukaryotes
-
Eukaryotic genes consist of DNA
segments that code for the amino acid sequence of proteins interrupted
by noncoding DNA segments
-
Eukaryotic cells may regulate
the transcription of individual genes, large parts of chromosomes, or entire
chromosomes
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