Transcript "Redundancy " & "Junk" for Codons

Mr. Gibson Biochemistry I Class
Lecture Hall - 213/Laboratory -214
Week of April 16, 2012
The "Redundancy
" & "Junk" for
Codons
Notice the amino acid.
Leucine (L)?
The "Redundancy
" & "Junk" for
Codons
Leu uses the (not only) one
set of codons within one of
our 16 code boxes that have
the same 1st two letters,
(but also) another box of
codons with another pair
of different 1st two letters –
although they are the same
within the that box, they
are different when
compared to the other box.
The "Redundancy
" & "Junk" for
Codons
GCU
GCC
GCA
GCG
Recent lab analysis has
A
shown there are
purposes for both [the]
“redundancy” & “junk”.
GCU
GCC
GCA
GCG
A
The "Redundancy
" & "Junk" for
Codons
Regarding [the] “redundancy”….
Let’s say the cell calls for the amino
acid shown here – alanine; to be
inserted at multiple points on the
polypeptide (multiple aminoacids) chain in a particular protein
…
The "Redundancy
" & "Junk" for
Codons
GCU
GCC
GCA
GCG
Regarding [the] “redundancy”….
A
The 1st two letters (nitrogenous
bases) guanine & cytosine – will
deliver a tRNA molecule with the
amino acid alanine covalently
bonded to its acceptor arm.
The "Redundancy
" & "Junk" for
Codons
GCU
GCC
GCA
GCG
Regarding [the] “junk”….
A
The 3rd letter (nitrogenous base) of
the codon makes no difference in
terms of delivering the correct
tRNA molecule with the alanine
amino acid covalently bonded to
its acceptor arm.
The "Redundancy
" & "Junk" for
Codons
GCU
GCC
GCA
GCG
Although the cell needs
(proteins) to (operate) and
A
(maintain) itself;
The "Redundancy
" & "Junk" for
Codons
GCU
GCC
GCA
GCG
The cell does not want proteins to
A
be… too many or too few for its
needed processes
OR
to hang around for too long or too
short of a time as it is being used.
The "Redundancy
" & "Junk" for
Codons
At a level of study that would be too
complex and take up too much time
for our understanding -- we can say
this:
Muliple codons with different 3rd
letters… do tell the proteins that
come out of the ribosome translation
process how long they are to hang
out in a cell once delivered…
The "Redundancy
" & "Junk" for
Codons
AND;
also tells the proteins how many
or few of them are to show up at
the cell (correct amounts) to
meet the cell’s needs.
The "Redundancy
" & "Junk" for
Codons
In fact…
If there are too many or too few
proteins
–or-
if they don’t break down (denature)
and go away thus hang around for too
short or long of a time;
a third type of disease occurs in all
living cells.
The "Redundancy
" & "Junk" for
Codons
As you may recall from your
biology class studies; there are two
types of diseases that destroy cells
(a) bacteria and (b) viruses.
The "Redundancy
" & "Junk" for
Codons
A third type of disease prion disease
all centers around the tRNA
bringing the correct amino acid
along with its correct directions in
terms of amount (expression) &
longevity (dwell time)for the
ribosome to make the protein
possessing the correct
structure/information-function [as]
dictated by the “redundant” &
“junk” codons/3rd letter.
The "Redundancy
" & "Junk" for
Codons
Prion diseases are always
debilitating and often fatal. Many,
many times it doesn’t even show up
in a living organism until much
later in its life cycle – and then, with
devastating results.
The "Redundancy
" & "Junk" for
Codons
A vivisection (cross-section) of a
human brain with areas that are
degenerating (breaking down…
getting soft or mushy);
A cow that is loosing the motor
function in its legs due to nerve
degradation (breaking down, no
longer able to carry electrical
impulses).
The "Redundancy
" & "Junk" for
Codons
We now have a glimpse into
understanding the nature, importance
and complicated directions that are
delivered by the codons as they relate to
amino acids and protein amounts/life
expectancy;
We will next look at the make up of the
“manufacturing site” – the ribosome – in
terms of its parts & functions of those
parts.