HOW DO CHANGES IN DNA
AFFECT PROTEIN SYNTHESIS?
W H Y I S I T I M P O R T A N T T H AT
GENE EXPRESSION IS
R E G U L AT E D ?
ALL OUR DNA IS FOUND INSIDE THE NUCLEUS OF EVERY
SINGLE CELL IN OUR BODY! (MINUS YOUR REPRODUCTIVE CELLS)
The DNA inside these
blood cells is exactly
the same as the DNA
in these nerve cells!
SO, IF WE HAVE THE SAME DNA IN ALL OUR CELLS… WHY
DON’T WE HAVE ARMS GROWING OUT OF OUR HEAD?!
OR EYEBALL PROTEINS BEING
MADE IN OUR HEART??!!
GENE EXPRESSION:
the processes by which the information in a gene is put to work.
When a gene is “expressed”, it is being actively coded into mRNA
and amino acid sequences (protein synthesis).
Not all of an organism’s DNA is expressed all of the time. For example, a heart cell
does not and cannot express the DNA that an eyeball expresses. Both of these
cells have the same DNA but are expressing different parts of the DNA.
Gene expression can be compared to a light switch…
Heart proteins will NOT be created if the
DNA strand is NOT being transcribed in the
heart cells themselves!
Eyeball proteins will be created if the DNA
strand is being transcribed in the eyeball
cells!
WHAT VARIES IN OUR DNA?
Mutations occur by changing the sequence of the
nitrogen bases in DNA, resulting in different
proteins.
Differences between organisms occur because the
sequence of the nitrogen bases is different in
each organism (mixture of both parents)
DNA MUTATIONS:
Mutation - Change in a DNA sequence that affects genetic
information; error or mistake in copying DNA.
POLYDACTYL
BABY WITH MASSIVE
AMOUNTS OF MUSCLE
ANIMALS WITH PIGMENT
(COLOR) MUTATIONS
2 TYPES OF MUTATIONS:
1. Point Mutations - Mutation that only affects a single
nucleotide at one point.
Substitution – one nucleotide base is changed, or
substituted for another.
This example of a
substitution would
Original: AUGUAC → Met – Tyr
cause the amino acid
Mutated: AUGUAG → Met – Stop
chain to stop protein
production too early!
2 TYPES OF MUTATIONS:
2. Frameshift Mutations - Mutation that shifts the reading
frame of the entire genetic code by inserting or deleting
a nucleotide.
Insertions – A base is added into the DNA sequence.
Deletions - A base is removed from the DNA sequence.
Original: The fat cat ate the wee rat.
Frame Shift: The fat caa tet hew eer at.
deletion
Frameshift mutations
affect all subsequent
amino acids after the
mutation takes place!
SIGNIFICANCE OF MUTATIONS
Many mutations have little or no effect on the
expression of genes.
Mutations may be harmful and may be the cause of
many genetic disorders and cancer.
Mutations may be a source of genetic variability in a
species (may be highly beneficial for the ecosystem).