MUTATIONS!
Part One
MUTATIONS:
WHAT ARE THEY ?
MUTATIONS:

are changes in the genetic material
of the cell.

can occur at the level of an
individual DNA strand (a point
mutation) or to an entire
chromosome (a chromosomal
mutation)
MUTATIONS:

usually lead to a decrease, rather
than an increase, of information.

A loss of information in the cell
leads to a loss of some function.
Information is lost….
Information is lost….
Information is lost….
Information is lost….
The loss of information
means that most
mutations are
either harmful
or have no effect.
The loss of information
means that most
mutations are
either harmful
or have no effect.
The loss of information
means that most
mutations are
either harmful
or have no effect.
The loss of information
means that most
mutations are
either harmful
or have no effect.
.
Now and then a mutation will
offer a benefit to an organism.
.
However, the idea that a single mutation would lead
to a huge, dramatic change in a single generation
(like the X-Men characters) is just wrong.
TYPES OF MUTATIONS:

Point mutations are caused by
random errors in the copying
process (during transcription)
TYPES OF MUTATIONS:

Chromosomal mutations occur
when chromosomes fail to properly
separate during meiosis
Chromosomal
Mutations:
chromosome
nucleosome
DNA
double
helix
coils
supercoils
histones
Chromosomal
Mutations:
• changes in the number
or structure of chromosomes
Chromosomal
Mutations:
•
changes in the number
or structure of chromosomes
•
typically harmful in humans
Chromosomal
Mutations:
• can occur in four different ways:
deletion, duplication, inversion
and translocation
Chromosomal
Mutations:
DELETION
Chromosomal
Mutations:
DELETION
DUPLICATION
Chromosomal
Mutations:
DELETION
DUPLICATION
INVERSION
Chromosomal
Mutations:
DELETION
DUPLICATION
INVERSION
TRANSLOCATION
Non-Disjunction:
•
is the failure of the chromosomes
to properly separate during
meiosis
Meiosis II:
Meiosis I: non-disjunction
homologous chromosomes
fail to separate
Non-Disjunction:
•
leads to organisms with the
wrong number of chromosomes
•
causes birth defects like Down’s
Syndrome (trisomy-21)
POINT
Mutations:
chromosome
nucleosome
DNA
double
helix
coils
supercoils
histones
POINT
Mutations:
• are changes in single base pairs of DNA
•
can lead to production of faulty
(misshapen) proteins, or no
protein at all
POINT
Mutations:
• often have no
effect: UCC
codes for
serine, for
example, but so
does UCU, UCA
or UCG
• that change the last letter in a DNA
triplet may lead to the same amino acid
POINT
Mutations:
• that do this are called sense or
silent mutations
POINT
Mutations:
• which lead to
a different
amino acid,
however, are
called missense
mutations
• Depending on the amino acid,
these can be good, bad or neutral
POINT
Mutations:
• which lead to
a stop codon
(UAA, UAG or
UGA) are called
nonsense
mutations
•
These lead to loss of function
and are usually bad
POINT
Mutations:
• Sense, missense and nonsense
mutations are typically caused
by substitution of one nucleotide
for another, changing the
meaning of only one codon.
•
Deletion or insertion of an entire
nucleotide leads to frameshift !
Frameshift Mutations
alter everything that follows:
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THE HOG ATE THE RAT MAN
THE DOG ATE HER ATM AN…
THE OGA TEH ERA TMA N…