Download Genetic Changes Chapter 11.3

Genetic Changes
Chapter 11.3
Any change in the DNA
sequence is called a
mutation.
Genetic changes
•
Mutations affect the reproductive
cells of an organism by changing
the sequence of nucleotides within a
gene in a sperm or an egg cell.
If Fertilization occurs

If fertilization occurs, the mutated
gene would be duplicated in the new
individual.
 This
mutation could result in several
different things:
 it could produce a new trait
 it could produce a defective protein
 it could cause structural or functional
problems in cells and organism.
 it could be so severe that the
embryo does not survive.
All living creatures have
genes, made up of DNA.
Without DNA mutations,
life on Earth could not
have evolved. Mutations
can affect the way a
gene works, which may
in turn cause changes in
an animal's appearance,
or behavior
. Sometimes, a new gene
variant may mean the
animal is better adapted
to its surroundings,
improving its chances of
survival. So this animal is
more likely to have
offspring, which will
inherit the beneficial
gene variant. This
process is called natural
selection.
Positive mutations
Some
rare mutations have
positive effects like increasing
or decreasing the speed of
certain reactions in the body.
 mutations that benefit a
species plays an important
role is the evolution of that
species.
Tortoises have evolved protective shells to retract
into when faced by predators.
Non reproductive cell mutation

If a mutation occurs in a nonreproductive cell, like a body cell,
the mutation will not be passed on
to the offspring.




It will affect or cause damage to the
organism.
It may impair the function of the cell.
Some mutations affect cell division,
like cancerous cells
They result in rapid cell division.
DNA Muscles

(AP) Somewhere in
Germany is an
extremely strong
toddler: born in Berlin
with bulging arm and
leg muscles. Not yet
5, he can hold sevenpound weights with
arms extended,
something many
adults cannot do. The
boy - whose name is
being withheld to
protect his privacy - is
reported to have
muscles twice the size
of other kids his age
and half their body
fat. Medical
researches say DNA
tests show the
reason: he has a
genetic mutation that
boosts muscle
growth.
Types of DNA mutations

There are three major types:
1. Point mutation
2. Frameshift mutation
3. Chromosomal mutations
Point mutation
 This
is a result
of an incorrect
base being
inserted into
the DNA
sequence.
 ex: TACCTC
could change
to TACCTT
resulting in a
new amino
acid.
point mutation



A point mutation is a simple change
in one base of the gene sequence.
This is equivalent to changing one
letter in a sentence, such as this
example, where we change the 'c' in
cat to an 'h':
Original
The fat cat ate
the wee rat.
Point Mutation
The fat hat ate
the wee rat.
Point mutation 2.
This
can cause the
wrong amino acid
to be produced,
resulting in the
wrong protein,
which could have
various affects on
the cell or
organism.
Point mutation and Sickle Cell


There is a certain
genetic disorder
known as Sickle Cell
Anemia. It causes a
warping of the blood
cells, so you get cells
like the one in the
bottom left:
This genetic trait will
cause less oxygen to
be delivered thought
the blood, causing
weakness and pain. It
differs from a normal
blood cell gene by
one, single point
mutation.
Frameshift mutation
When
a base is added or
deleted from the DNA
sequence:
 ex: TACCTC could mutate
into TACACTC or TACTC



An example of a frame-shift
mutation using our sample sentence
is when the 't' from cat is removed,
but we keep the original letter
spacing:
Original
The fat cat ate the wee
rat.
Frame Shift The fat caa tet hew
eer at.
Frameshift mutation 2.

This will shift the reading of the
codons. Therefore, resulting in an
incorrect amino acid chain.
Chromosomal mutations
These
are mutations in the
formation of the chromosome
where:
 parts of the chromosome
may break off and become
lost in the cell during
mitosis or meiosis
 chromosomes may rejoin
incorrectly
Chromosomal mutations 2.
These
types of mutations are
more common in plants.
Few of these mutations are
passed on to offspring
because more than likely the
zygote does not survive.
Causes of Mutations


Mistakes in base pairing can occur
during DNA transcription or
replication
Mutations are also caused by
environmental factors.


A mutagen is any agent that can cause
a change in DNA.
They include things such as chemicals,
high energy radiation and high
temperatures.
Mutations 2

Mutations in cells are sometimes
fixed by the body’s own self-check
system.

There are proof-reading enzymes inside
the cell that check the DNA after
replication or transcription that insert
or delete incorrect base pairs.
Mutations 3


Like most living things, it is not a
perfect process, but works
extremely well… just like a spell
check on your computer fixes
most things, it still skips over
things that seem to make sense,
but don’t.
Ex: if you meant to write the word dye,
but put die instead… spell check probably
won’t catch it.
Aging is said to be a possible genetic mutation