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The Central Dogma – V2
In 1869, Friedrich Miescher isolated nuclein. Between
1900 and 1935, Phoebus Levene studied nucleic acid
and described DNA and RNA.
By the 1930’s other scientists had worked out that
amino acids peptide bonded to make proteins. They
knew that proteins made up the structures of living
organisms and were folded into many complex shapes.
For a while proteins were though be the inherited
“factors”. By the 1930’s scientists knew that DNA
was inherited, not proteins. Now they began
searching for the connection between DNA in the
nucleus, and RNA and proteins made in the cytoplasm.
Fredrick Sanger worked with the protein insulin. He
determined the amino acid sequence that made up
insulin and how the protein folded.
Next James Crick worked on the central dogma.
He asked the critical question:
“How can 4 different nucleotides code for 20 amino
acids?” or “How can A,T, G, C tell the cell to correctly
order 20 amino acids into complex proteins?”.
Answer:
1 codon of 3 RNA nucleotides  codes for 1 amino acid
(see text p. 253 fig 8.2) The genetic code always
uses “words” with exactly three “letters” or RNA
nucleotides.
RNA to Amino Acid TRANSLATION CHART
This chart is used to translate mRNA to a
polypeptide. Codons are an RNA “word” with 3 RNA
nucleotides. Each codon matches one amino acid
except the 3 stop codons. Many amino acids have more
than one codon due to redundancy.
What are the 3 RNA nitrogen bases that make up
each of the stop codons?
List the codons that code for glutamic acid:
Central Dogma
A dogma is a powerful theory with little experimental
support. Now there is proof of the dogma proposed
by Crick.
1. transcription
DNA
2. translation
RNA
3. protein
synthesis
amino acid
protein
1. transcription of DNA template strand to mRNA
DNA coding strand
DNA template strand
ATG GGA TTC
TAC CCT AAG
transcribed mRNA
AUG GGA UUC
2. translation of mRNA to amino acid sequence
mRNA
AUG GGA UUC
translated amino acid
met gly phe
Note : each amino acid has a 3 letter nickname
met – methionine, gly – glycine
Characteristics of the DNA to RNA Code
1. Continuity: The codons are read as an unbroken series of
non-overlapping three letter words.
Example: THE DOG ATE THE CAT
Mutations can add, delete or substitute a nucleotide.
Adding or deleting nucleotides causes a reading
frameshift.
2. Redundancy: 64 possible codons but only 20 amino acids,
different codons for the same amino acid. Glycine
triplets include GGU, GGC and GGA. Substitution
mutations in the last position are often neutral. This is
the “wobble hypothesis”.
3. Universality: The same RNA codons correspond to the
same amino acids in almost all organisms. This is proof of
a common ancestor and allows for genetic modification.
This is incredibly strong evidence in support of evolution.
The Central Dogma – V2
In 1869, Friedrich Miescher isolated ___________________. Between 1900 and 1935,
Phoebus Levene studied nucleic acid and described ___________________.
By the 1930’s other scientists had worked out that __________________________ to
make __________________. They knew that proteins made up the structures of living
organisms and were folded into many complex shapes.
For a while proteins were though be the inherited “factors”. By the 1930’s scientists knew
that ______________ was inherited, not proteins. Now they began searching for the
connection between DNA in the nucleus, and _________________ made in the _______.
Fredrick Sanger worked with the protein ___________. He determined the _______
______________ that made up insulin and how the protein folded.
Next James Crick worked on the _________________.
He asked the critical question:
“How can 4 different nucleotides code for 20 amino acids?” or “How can A, T, G, C tell the
cell to correctly order 20 amino acids into complex proteins?”.
Answer:
__________________________________________________________
(see text p. 253 fig 8.2) The genetic code always uses “words” with exactly three
“letters” or RNA nucleotides.
RNA to Amino Acid TRANSLATION CHART
This chart is used to translate mRNA to a polypeptide. ____________ are an RNA “word”
with 3 RNA nucleotides. Each codon _________________________ except the 3 stop
codons. Many amino acids have more than one codon due to ____________________.
What are the 3 RNA nitrogen bases that make up each of the stop codons? _________
List the codons that code for glutamic acid: ______________________
Central Dogma
A dogma is a powerful theory with little experimental support. Now there is _________
of the dogma proposed by Crick.
1.___________
DNA
3. _______
_________
2. __________
RNA
amino acid
protein
1. _________________________________________
DNA coding strand
DNA template strand
ATG GGA TTC
_____________
transcribed mRNA
_____________
2. ______________ of _______ to amino acid sequence
mRNA
_____________
translated amino acid
______________
Note : each amino acid has a 3 letter nickname met – methionine, gly – glycine
Characteristics of the DNA to RNA Code
1.
_______________: The codons are read as an _______________________
of non-overlapping three letter words.
Example: THE DOG ATE THE CAT
______________ can add, delete or substitute a nucleotide. Adding or deleting
nucleotides causes a _______________________________
2.
_________________: 64 possible codons but only 20 amino acids, ________ codons
for the _____ amino acid. Glycine triplets include GGU, GGC and GGA. Substitution
mutations in the last position are often neutral. This is the ___________________
3.
_______________: The ____________________ correspond to the __________
_______ in almost all organisms. This is proof of a ____________ and allows for
genetic modification. This is incredibly strong evidence in support of evolution.
Complete the attached worksheet.
Read text p 252 – 256. Do p 256 # 2, 4, 5, 6