Download Mutations

A cell begins to
produce a new type
of protein. This is
most likely due to an
alteration of the
(1) structure of the cell
membrane
(2) sequence of bases
in a section of a
chromosome
(3) chemical makeup
of the cytoplasm
(4) shape of the
antibodies produced

1
Why
is variation
important?
How does variation
come about?
2
Sexual reproduction brings about variation.
 The offspring are genetically different from
either parent.
 Genetic variation allows a species to adapt
to a changing environment. This can lead to
evolution of the species.
 Most variation is the result of segregation
and crossing over during meiosis and
recombination during fertilization.
 Another way to get variations is through
mutations.

3






A mutation is a sudden change in the genetic
material.
Gene mutations occur randomly and can
occur in any cell.
Mutations can happen accidentally or can
be caused by radiation or toxic chemicals.
A mutation in a single body cell does not
pose any real threat.
For a mutation to be inherited it must occur in
a sex cell or gamete.
At the time of fertilization, the mutated
gamete passes on the mutation to all the cells
of the offspring.
4
5
6
• A change in the structure of a chromosome.
• Normal order of genes: ABCDEFG
› Translocation
› Inversion
› A piece from another
› Part of chromosome is
chromosome
attaches
 ABCDEFGXYZ
› Addition
› Adding on a piece
from the homologue
 ABCABCDEFG
turned around
 ABEDCFG
› Deletion
› Part of chromosome is
missing
 ABCFG
Missing a
piece
7
8
What
is
nondisjunction?
9
Nondisjunction – the addition or loss of a
whole chromosome. It is caused when
chromosomes fail to separate during
meiosis.
 Down,
 Patau,
 Turner,
 Edward’s
syndromes.

10
11
The substitution of
one nucleotide for
another.
ATG-CGT-TAA
ATG-GGT-TAA


›
›
changing one base
might result in a
defective protein
Sickle Cell Anemia
has a Valine instead
of Glutamic Acid
(Glutamate)
12
When nucleotides
are added or
deleted all the
codons beyond
that point are
changed.
Example:


ATCGCGGTAACA
ATCGGTAACA…..
THE DOG ATE THE CAT THE DOG GOT SIC
THE GAT ETH ECA TTH EDO GGO TSI C
13
14
15
A
normal sequence of DNA bases in a
single human skin cell is CATGGC. If
this sequence replicates in this cell and
becomes GATGGC, this alteration will
most likely be passed to
› (1) every cell that develops from it
› (2) all human body cells
› (3) offspring of the human
› (4) all skin cells of this person
16

A pedigree chart
allows geneticist to
trace a condition
through a family
and predict where it
may occur in the
future:
›
›
›
›
›
Squares = Males
Circles = Females
Filled = Has condition
Empty = Normal
Half = Carrier
A typical X-linked recessive trait
that is found mainly in males,
but females are carriers, and
often skips a generation.
17
18



Some genetic
disorders may be
detected before
birth.
Biochemical tests
may be done to
look for a chemical
disorder such as
PKU.
Ultrasound may be
used to detect
physical disorder.
19
20
21



PKU is caused by a
defective gene on
an autosome for an
enzyme that breaks
down phenylalanine.
Without the enzyme
phenylalanine builds
up and damages
the baby’s brain.
A simple blood test
can detect PKU &
diet can control it.
22
A karyotype can be
used to detect
chromosomal
disorders caused by
nondisjunction.
 It is made by
photographing the
chromosomes from a
human cell and
arranging them in
pairs.
 A geneticist may then
look for any
abnormal pairs.

23



Testing of the amniotic
fluid that surrounds the
baby in the uterus is
called amniocentesis.
It is performed
between the 13th and
18th week of
pregnancy.
The purpose of the test
is to count and
analyze the number of
chromosomes present.
24


Chorionic villus
sampling (CVS) is a
prenatal test that
involves taking a
sample of some of the
placental tissue.
This tissue contains the
same genetic material
as the fetus and can
be tested for
chromosomal
abnormalities and
some other genetic
problems.
25
Why
might humans
selectively breed an
organism?
26

Selective breeding
› Individuals showing
the desired traits are
purposely chosen
for mating.

Inbreeding
› The mating of
closely related
individuals to obtain
desired
characteristics.
› Used to produce
purebred domestic
animals.
Foxes become dog-like with
selective breeding.
27
A
sudden change in
the DNA of cells
developing in which
organ could be passed
to future generations?
(1) A
(2) B
(3) C
(4) D
We can identify and locate individual
genes, which means genes can be
Removed, put together, and recombined:
1. Cut out the desired DNA of the gene
2. Combine that DNA with that of the
recipient
3. Insert it into the new organism
33
Restriction enzymes
recognize specific
sequences of DNA
bases and split each
DNA strand at a
specific site within
that sequence.
 This one recognizes
the base sequence
"G-A-A T-T-C" and cuts
each strand between
the "G" and the "A" as
shown by the red
arrow.

36
Pieces of DNA from
one organism can
be spliced (glued)
into DNA of another
organism using an
enzyme.
 The recombinant
DNA is then put into
The recombinant cell follows
a new organism.

the instructions from the new
DNA
37

Vectors (Carriers)
•
•
carry pieces of DNA from one location to
another
Types of Vectors:

bacterial plasmids
• small circular pieces of DNA
• they have the ability to replicate in another
cell

viruses
• DNA can be added to the virus’ DNA
• virus infects a host cell & inserts its DNA
38
A bacterial plasmid
(chromosome) is cut
open with a restriction
enzyme.
 The same enzyme is
used to cut out the
human gene for insulin.
 These cut pieces of DNA
are put together and
their “sticky” ends
attach to each other.
 The recombinant
plasmid is now placed
inside of a bacterium to
produce insulin.

39
Gel
Electrophoresis




Proteins and Nucleic
Acids are separated
by running them
through an electrified
gel.
Restriction Enzymes
are used to cut the
DNA into different size
pieces.
The large pieces
move slowly, while
the small pieces
move quickly.
This is sometimes
called DNA
fingerprinting.
45
The Polymerase Chain
Reaction (PCR) can
make billions of copies
of DNA in a short time.
 The DNA is doubled at
each cycle and at the
end of 32 cycles it has
been amplified 1 billion
times.
 A cycle can be done
in as little as 17
seconds, so it is
possible to get a billionfold amplification in
less than an hour.

46
1. DNA
Evidence is
multiplied
using PCR.
2. Then it is
separated
using gel
electrophore
sis.
47
The nucleus is removed
from an unfertilized egg.
 The nucleus from a
donor cell is transferred
into the egg.
 The diploid (2n) egg is
then implanted into a
foster mother to grow.
 The lamb is identical to
the donor.

51