Download UNIT 4 PART 2 APPLIED GENETICS

UNIT 4 PART 2: APPLIED GENETICS
• 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.
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MUTATIONS
• 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.
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CHROMOSOMAL MUTATIONS
• A change in the structure of a chromosome.
• Normal order of genes: ABCDEFG
– Translocation
– A piece from another
chromosome attaches
• ABCDEFGXYZ
– Inversion
– Part of chromosome is
turned around
• ABEDCFG
– Addition
– Adding on a piece
from the homologue
• ABCABCDEFG
– Deletion
– Part of chromosome is
missing
• ABCFG
Missing a
piece
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NONDISJUNCTION
• 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.
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GENE MUTATIONS- POINT MUTATIONS
•
•
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)
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GENE MUTATIONS- FRAMESHIFT
MUTATIONS
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
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PEDIGREE CHART
• 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.
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GENETIC SCREENING
• 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.
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PHENYLKETONURIA - PKU
• 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.
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KARYOTYPE
• 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.
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AMNIOCENTISIS
• 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.
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CHORIONIC VILLUS SAMPLING
• 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.
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Genetics can be used to produce organisms
with desired traits.
• 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.
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GENETIC ENGINEERING
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
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STEP ONE: ISOLATING DNA
Restriction Enzymes
• 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
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the red arrow.
STEP TWO: RECOMBINING DNA
•
•
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 a new
The recombinant cell follows
organism.
the instructions from the new
DNA
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STEP THREE: INSERTING THE
DNA
•
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
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Recombinant Genetics: Insulin
• 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.
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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
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fingerprinting.
PCR
Polymerase Chain
Reaction
• 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
billion-fold amplification
in less than an hour.
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Use of PCR in
Forensic Science
1. DNA Evidence is
multiplied using PCR.
2. Then it is separated
using gel
electrophoresis.
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Cloning
• 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.
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