Transcript The Secret Code of Life:

The Secret Code of Life:
“The Cellville Cipher”
Genome British Columbia, 2004
www.genomicseducation.ca
Codes and Ciphers:
• The Pigpen code will work to
encode secret messages only
if the other person receiving
the message knows the key
• Codes were made as a means
of sending information easily
such as the Morse code, or to
send secret information – short
and secret
• A code replaces words,
phrases or sentences with
numbers or letters while a
cipher rearranges the letters to
further disguise the message
Can you decipher this? Can you
decode this message?
• There are no secrets
better kept than the
secrets that everybody
guesses."
• This is the pigpen cipher,
an original French cipher,
that was used by groups
such as Napolean’s spies
to send secret messages
Why does the human body need a
code?
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The nucleus has an amazing
design of sending information
quickly to the rest of the cell
(function is to control the cells
functions)
The nucleus houses the DNA
which owns the genetic code.
The stored information in the DNA
needs to transfer it’s information
quickly and reliably into a product.
The information is stored in
packets or “files” called genes.
Genes are places or locations on
a chromosome that contain a
specific piece of information for
the creation of a protein. The
transfer of this information is
called PROTEIN SYNTHESIS.
The Central Dogma
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The central dogma or “idea” of the
transmission of information in the cell is:
Transcription
Translation
• DNA  RNA  PROTEIN
• Where, DNA is read and transfers the
information of the blueprint of the protein
to RNA, and RNA transfers this
information to be created in the
cytoplasm
• Transcription + Translation = Protein
Synthesis
• On your worksheets, which represents
the RNA? Which represents the
protein?
The Genetic Code
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The DNA has a triplet code using only
the 4 nucleotides, A,C,G and T. Only 3
nucleotides form a triplet which, when in
a gene, codes for a part of a protein.
There are 34 total different triplets that
can be created but only 20 different
amino acids. (Would a doublet code work
just as well?? i.e. only 2 nucleotides to
represent 20 amino acids. Why are there
a lot of codes that mean the same amino
acid?)
Many triplets in a specific order will
generate a specific protein (this is based
on the order of the bases in the DNA)
The bottom line is that the genes we
have in our DNA create PROTEINS
which we need.
These proteins are made up of amino
acids joined together in a specific
manner to create the protein needed.
There are 3 stop codons which tell the
machinery not to continue the protein
synthesis process.
Example
• TAC GCT TAA CGG ACT TTA
• ATG CGA ATT GCC TGA AAT
• DNA
STRANDS
• AUG CGA AUU GCC UGA
• mRNA
• Met – Arg – Ile – Ala – stop
• Protein
MUTATIONS – When the code is
changed!
• A mutation is a change in the DNA from its
original form (mutatio = change, alteration
in Latin)
• When just one base is changed in the
DNA, it is considered a mutation. It would
also create a new allele for the gene. Not
all mutations are harmful.
Types of Mutations
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A. Chromosomal Mutations
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Aneuploidy or a loss or gain of a whole chromosome:
occurs when mitosis or meiosis doesn’t function correctly
and causes a cell to have 46 +/or- 1 or 2 chromosomes e.g.
X0 = Turner’s syndrome
Polyploidy or a loss or gain of a whole set of
chromosomes: instead of having 46 chromosomes, an
additional 23 chromosomes are added or 23 are lost! (not
found in humans but can occur in plants!!)
Loss of a part of an arm of a chromosome = translocation.
This occurs when the arm of one chromosome is attached to
a different chromosome. (Could be reciprocal where both
arms are attached to the other recipient chromosome)
Inversions: where a portion of a chromosome rearranges
the order of the DNA inside the arm
Deletions: a large piece of DNA is taken out of the
chromosome
Duplication: a large segment of DNA is copied and inserted
beside its original sequence.
Insertion: a large piece of DNA coming from one
chromosome and put into another
Types of Mutations
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B. Point Mutations
– i) Insertion: 1 or 2 bases are added to
DNA at one place (not in multiples of 3 –
why is that?)
• These mutations can cause serious
effects if it occurs within a gene as
the triplet sequence will be
disrupted
– ii) Deletion: 1 or 2 bases are added to
DNA at one place (not in multiples of 3 –
why is that?)
• These mutations can cause serious
effects as well if it occurs within a
gene as the triplet sequence is
disrupted
– Iii) Substitution: of 1 base for another
base e.g. A  T or G  C
• These mutations may or may not be
harmful depending on where the
change in the gene occurs and the
effect of this change on the
resulting amino acid that it is
changed to.
i)TAC GCT AGG ATG
TAC GGC TAG GAT G
ii) TAC GCT AGG ATG
TAC CTA GGA TG
iii)TAC GCT AGG ATG
TAC ACT AGG ATG
Effects of mutations on Proteins
• Positive – causes the protein
to be have an even better
function/ does its job better
(this will allow for natural
selection and evolution)
• Negative – causes the protein
to have little or no function OR
disrupts another protein’s
function e.g. Sickle cell
anemia
• Neutral – causes the protein to
have no significant change in
function (many are in this
category such that we never
see disease from these
mutations)
Effects of DNA changes on
Proteins
A. Normal protein
B. Neutral mutation
No change in
the active site
C. Negative mutation
No
active
sites
D. Positive mutation
2 active sites
now, more
effective
protein
Bibliography and Credits
http://www.nationalarchives.gov.uk/online/spies/codema
ster/default.asp
http://www.accessexcellence.org/AB/GG/mutation2.html
http://www.people.virginia.edu/~rjh9u/code.html
http://www.nationalarchives.gov.uk/online/spies/codema
ster/default.asp
http://www.accessexcellence.org/AB/GG/dna2.html
http://www.accessexcellence.org/AB/GG/mRNA.html
Genome British Columbia, 2004
www.genomicseducation.ca