Transcript The Nobel Prize in Medicine

A presentation on…
The Nobel Prize in
Medicine - 1968
By,
Anusha Teegala
Nobel Prizes 1968
The beginning of Genetics as a Science
Exactly 100 years back since 1968….
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1866 - Gregor Mendel – Discovers from very simple
experiments with peas that our inheritance is packaged into
many independent genes.
1868 - Friedrich Miescher (Father of genetics) - isolated
nucleic acid from cell nuclei.
1944 - Avery - Link established – Genes contain nucleic
acids.
Nucleic acids - composed of nucleotide chains that convey
genetic information.
Genes – Has a sequence of codons which inturn specify the
amino-acid sequence of the encoded protein.
Genetic Code of Life
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What is Genetic Code?
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Set of rules by which information encoded in genetic material
(DNA or RNA sequences) is translated into proteins (amino
acid sequences) by living cells.
Why is it called the code of Life?
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These rules describes all our inherited traits.
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The genetic code is the dictionary that translates the
nucleic alphabets to corresponding protein alphabets
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Aim: To crack the code – Our three musketeers to the
rescue….
Marshall W. Nirenberg
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Devises a translation-machine
 Feed this machine with nucleic acid
alphabets and it returns corresponding
alphabets in protiens.
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Synthesized a very simple nucleic acid,
composed of a chain of only a single repeating
letter. Using this nucleic acid the system
produced a protein which also contained a
single letter, now written in the protein
alphabet.
Nirenberg’s Research Approach
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Various combinations of mRNA were passed through a filter which
contained ribosomes.
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Unique triplets promoted the binding of specific tRNAs to the
ribosome.
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By associating the tRNA with its specific amino acid, it was
possible to determine the triplet mRNA sequence that coded for
each amino acid.
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He got the wheel rolling… In less than five years, along with
Khorana, establishes the Genetic Code.
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Presently –involved in investigation of various aspects of
neurobiology.
Har Gobind Khorana
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Systematically devises methods which led to the
synthesis of well defined nucleic acids, giant
molecules with every building block in its exact
position.
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His synthetic nucleic acids were a pre-requisite
for the final solution of the genetic code.
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Currently: At MIT, Works on molecular
mechanisms of visual transduction in the
vertebrate photoreceptor cells.
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Trivia - Khorana, US Citizen.
Khorana’s Research Approach
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(RNA) with two repeating units (UCUCUCU → UCU CUC
UCU) produced two alternating amino acids. This, combined
with the Nirenberg and Leder experiment, showed that UCU
codes for Serine and CUC codes for Leucine.
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RNAs with three repeating units (UACUACUA → UAC UAC
UAC, or ACU ACU ACU, or CUA CUA CUA) produced three
different strings of amino acids.
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RNAs with four repeating units including UAG, UAA, or UGA,
produced only dipeptides and tripeptides thus revealing
that UAG, UAA and UGA are stop codons.
Invention of Khorana
- Oligonucleotides
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Oligonucleotides – Short strings of nucleotides, custom built
artificial genes.
Oligonucleotides are often used as probes for detecting
complementary DNA or RNA because they bind readily to their
complements
widely used in biology labs for sequencing, cloning and
engineering new plants and animals.
Composed of DNA, are often used in the polymerase chain
reaction (PCR), a procedure that can be employed to amplify
almost any piece of DNA.
This invention of Dr. Khorana has become automated and
commercialized so that anyone now can order a synthetic gene
from any of a number of companies-- one merely needs to fax the
genetic sequence to one of the companies to receive an
oligonucleotide with the desired sequence.
Further reference can be found at:
http://www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2003/Holmberg/olig
onucleotide_synthesis.htm
Robert W. Holley
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What is the mechanism for the translation of the
code within the cell?
He is one of the discoverers of a special type of nucleic
acid which has been called transfer-RNA.
tRNA - has the capacity to read off the genetic code and
to transform it to the protein alphabet.
After many years of work Holley succeeds in preparing a
tRNA in pure form, in 1965, established its exact
chemical structure.
Holley's work represents the first determination of the
complete chemical structure of a biologically active
nucleic acid.
Holley’s Research Approach
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Holley's team of researchers determined the tRNA's
structure by using two ribonucleases to split the tRNA
molecule into pieces. Each enzyme split the molecule at
location points for specific nucleotides.
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By a process of "puzzling out" the structure of the pieces
split by the two different enzymes, then comparing the
pieces from both enzyme splits, the team eventually
determined the entire structure of the molecule.
Trivia…
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1958 Nobel Laureate, Edward Tatum (discovered that the
genes control production of enzymes) predicted that it
might take a lifetime to crack the code. But these three
scientists take the bio-community by surprise, they crack
the code in less than three years.
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Part of chapter 2 is all thanks to them.
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How far have we come since 1968?
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Conviction based on DNA Finger printing
Genetically engineered food
Dolly – First adult animal clone
Thank you!
Questions?
References,
Nobelprize.org
Wikipedia.org