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Mutations
If everyone on Earth is 99.9% identical, then how did that 0.1%
happen? How did everyone on Earth start to look different? These
differences in genetic material between members of a population can
be traced back to occurrences called MUTATIONS.
A MUTATION is a sudden change in the structure or the amount of
genetic material, namely your DNA.
Are mutations harmful?
Yes, some are, but many more are beneficial to us. Without
mutations, we would have no variation within a species.
Kinds of Mutations
Plant breeders and animal breeders have known for a while, that
while breeding, a species may suddenly be born with a trait that has
never appeared in that species before. The first individual born with
an abnormal trait is known as a MUTANT.
When talking about mutations, there are two main types…
-
CHROMOSOMAL MUTATIONS
o A chromosomal mutation is an abnormal change in the
structure of all or part of a chromosome, or a change in the
number of chromosomes an organism has.
-
GENE MUTATIONS
o A change that affects a gene on a chromosome, specifically
changing the base pairs on DNA or the order in which the
base pairs match up.
If a mutation occurs in one of these two manners, the possibility of
that mutation passing on to further generations can increase. If a
mutation only occurs in isolated cells, such as in cancer, the chances
of passing this on to the offspring are much, much less.
Causes of Mutations
Scientists have studied the possible causes of mutations within
various organisms. Mutations appear to happen naturally at a low
rate, but there are many factors that can possibly increase the chance
of a mutation occurring in the body…These factors that increase the
chances of a mutation are called MUTAGENS.
Possible Mutagens…
Radiation (UV Rays, X-Rays, etc)
Chemicals
o CARCINOGENS
High Heat
Chromosomal Mutations
Permanent changes in chromosome structure sometimes take place
during cell division. Chromosomes may become tangled or
rearranged in several ways which cause the chromosome to be
misread. The following are a few types of chromosomal mutations…
Normal Chromosome
TRANSLOCATION
The accidental attachment of a portion of another
chromosome to the original.
INVERSION
The accidental reversal of portions of the chromosome
ADDITION
The accidental repetition of a portion of the chromosome
DELETION
Part of the chromosome accidentally breaks off, leaving a
partial chromosome.
Gene Mutations
Genes, which are within a chromosome are composed of the
thousands of nitrogen bases which make up the DNA strand. Any
change in this sequence, will change the message given to the mRNA,
which will in turn, change the amino acids that will be called on to
assemble a particular protein. One small change in this order can
change the entire protein, or at least make the protein malfunction.
POINT MUTATION
A point mutation is a gene mutation in which only a single
letter accidentally changed.
THE BOG DOG ATE THE MAD CAT
o If a single letter is changed, the meaning of the sentence
changes…
THE BOG FOG ATE THE MAD CAT
-
ATC GAT TAC ATG CCT GAT
o (DNA)“GAT”  (RNA)“CUA”  (Am.Acid) Leucine
-
ATC CAT TAC ATG CCT GAT
o (DNA)“CAT”  (RNA)“GUA”  (Am.Acid) Valine
FRAMESHIFT MUTATION
In a frameshift mutation, an entire nitrogen base is
accidentally added or subtracted, causing the entire strand of
DNA to be shifted up one letter, or be shifted down one letter,
causing the codons to be misread, entirely changing the whole
protein instructions.
-
-
THE BOG DOG ATE THE MAD CAT
o A letter is added…
THE GBO GDO GAT ETH EMA DCA T
o The codon sequence no longer makes any sense.
THE BOG DOG ATE THE MAD CAT
o A letter is left out…
THE OGD OGA TET HEM ADC AT
ATC GAT TAC ATG CCT GAT
o A letter is added…
ATC TGA TTA CAT GCC TGA T
-
ATC GAT TAC ATG CCT GAT
o A letter is left out…
ATC ATT ACA TGC CTG AT