Download Genetics Lecture V

Genetics Lecture V
Mutations and Genetic
Modification
Biology Standards Covered
Std 4c ~ students know how mutations in the
DNA sequence of a gene may or may not
affect the expression of the gene or the
sequence of amino acids in an encoded protein
 Std 5c ~ students know how genetic
engineering (biotechnology) is used to
produce novel biochemical and agricultural
products

Mutations



Mutations are changes in
the DNA sequence that
affect genetic
information
Genetic mutations result
from changes in a single
gene
Chromosomal mutations
involve changes in whole
chromosomes
Mutations

Mutations that only affect one nucleotide are
called point mutations

Point mutations generally only affect one amino
acid in the sequence
THE DOG BIT THE CAT
THE DOG BIT THE CAR
Normal: AUG-AAG-GGC-UAA
Protein: Met - Lys - Gly - Stop
Normal: AUG-AAG-AGC-UAA
Protein: Met - Lys - Ser - Stop
Mutations

Frameshift mutations are much more
dangerous to the genetic code!
 They occur when a nucleotide is added
(inserted) or deleted
 This “shifts” the reading frame of the gene
THE DOG BIT THE CAT
** What happens if you remove the “G” in DOG
THE DOB ITT HEC AT
**The same would happen if you added a letter
Gene Mutations:
Substitution, Insertion, and
Deletion
Substitution
Insertion
Deletion
Mutations can be very dangerous
and VERY SCARY!!
Mutations

Chromosomal mutations involves the change
in the number or structure of chromosomes

There are Four Types:
Deletion – the loss of all or part of a chromosome
 Duplication – when a segment of a chromosome is
repeated
 Inversion – When part of a chromosome becomes
oriented in the reverse direction
 Translocation – when part of a chromosome breaks
off and attaches to another

Chromosomal Mutations
Deletion
Duplication
Inversion
Translocation
Selective Breeding
 selective
breeding – allowing only
desired traits or characteristics to be
passed on from one generation of
organism to the next
 This process requires time, patience, and
several generations of offspring before the
desired effect is achieved
Selective Breeding

By “selective breeding” we mean to:
 Actively “select” desired traits or
characteristics such as fruit shape, size, or
color (like in tomatoes for example)
 Through several generations, we breed for
those desired traits until the “frequency of
the allele” is increased
 This is a means to increase the “likelihood”
that these desired traits will appear
Selective Breeding
 Nearly
all domestic animals such as
horses, cats, dogs, and farm animals
as well as many crops have been
produced by selective breeding
 The “famous” scientist Luther Burbank
produced a disease resistant potato
plant that saved Ireland from the
“Potato Blight”
Selective Breeding
 One
of the
techniques that
Luther used was
hybridization –
crossing dissimilar
organisms to bring
together the best
of both organisms
Selective Breeding

Hybrids :
 Hybrids
are often
“hardier” than both
of the parents
 They are more
resistant to diseases
as well as
temperatures and
whatever they have
been selectively
bred to “resist”
Selective Breeding

Hybrids continued
In many cases
scientists have
“hybridized” a plant
with a high tolerance
for diseases with a
plant that produces
large amounts of food
 These are called
genetically modified
crops


This is a special hybrid of
extremely disease resistant
and large spinach
Selective Breeding
 Inbreeding
– mating between
closely related individuals
Selective Breeding
Inbreeding ensures
that the offspring are
homozygous for
most traits
 Inbreeding also can
increase the likelihood
of harmful recessive
traits as well

Increasing Variation
 Nature
already produces huge
“variety” known as variation
 We can see the HUGE diversity
in the human species
 “Breeders”
can increase the
variation in a population by
“inducing” mutations (making
them happen)
Increasing Variation


Breeders and scientists
use “mutations” to
increase variation in the
population
Mutation – a heritable
change in the DNA


ONLY if it can be “passed”
to the offspring
Mutations occur regularly
and are one of the
factors in evolution.
Sometimes, mutations
are negative 
Genetic Modifications

Polyploid – more
than the normal
amount of
chromosomes in an
organism
 Plants are often
engineered to be
polyploid so that
they are larger and
sometimes stronger
Manipulating and
Recombining DNA

Each living organism has it’s own specific DNA
that identifies that organism as an individual
 Think of DNA as a fingerprint
 Even each human, although we are all
“humans”, we all have slightly different DNA
 Except
clones
identical twins which are considered living
Manipulating and
Recombining DNA

What if we could
take segments of
DNA and “create”
any type of living
organism we
wanted?

TODAY – scientists
have ways of
doing just that !!
Manipulating and
Recombining DNA
Scientists are using the information they have
gathered so far about the structure of DNA to
“cut & paste” their own sections
 Scientists are able to “re-write” certain DNA
codes and alter living organisms
 Once you know the base-pairing rules you can
cut out sections of DNA and insert sections
wherever you wish

Genetic Engineering

Genetic
Engineering –
Restriction Enzymes cut DNA
making changes in
the DNA code of a
DNA
living organism

Restriction
enzymes act like
“keys” that fit into
specific sequences
of the DNA and
“cut” them
Restriction enzyme
cuts the DNA at
specific site
Sticky end
Tools of Molecular Biology
 DNA
Extraction – process by which DNA
 DNA
Cutting – this is done by the
is taken out of (extracted) from the cells
of an organism
restriction enzymes
 Separating
DNA – a process called gel
electrophoresis is used to separate DNA
into small fragments
Gel Electrophoresis


After the DNA plus restriction enzymes are
added to the gel, an electric charge is passed
through the gel
The genes separate out depending on size and
the smaller genes move “faster” through the gel
DNA plus restriction
enzyme
Power
source
Longer
fragments
Mixture of
DNA
fragments
Gel
Shorter
fragments
Cutting and Pasting
DNA

Recombinant DNA – when DNA is taken
from one organism and incorporated
into the DNA of another organism

Think of a gene that any plant or
animal would have that you would like
“spliced” into your DNA --- what gene
would you want?
Making Copies of Genes
Copies of genes need to be made so that
scientists can study them further
 The process of “copying DNA” is known
as the polymerase chain reaction


Have any idea why it is called that?
 Hint:
“Polymerase”
Cell Transformation

Cell transformation is when a
cell takes in DNA from outside
Recombinant DNA
the cell and it becomes part of
the “host” cell’s DNA
Target
 In order for you to
gene
Flanking sequences match
“recombine” DNA into
HOST
another organism you first
Recombinant DNA
have to get the gene from an
replaces target gene
organism
Host Cell DNA
 Your next step is to get it into
the cell you intend on
incorporating it into it’s DNA
Modified Host Cell DNA
Cell Transformation
 Transforming
EcoRI ~ restriction enzyme
removes the target gene
Recombined
plasmid
Bacteria

Plasmid – a small,
circular DNA molecule
 Found naturally in
most bacteria
 Plasmids are easy to
work with and can be
recombined outside
of the cell, then
placed back into the
cell
Animal cell
with Nucleus
Bacterial
chromosome
Plasmid
Bacterial
plasmid opened
by restriction
enzyme
Making Recombinant DNA in Bacterial Cells
Gene for
human growth
hormone
Human
Human
CellCell
Bacterial Cell
Sticky ends
Bacterial
chromosome
Plasmid
Recombinant
DNA
Gene for human
growth hormone
DNA
recombination
DNA
insertion
Bacterial cell for
containing gene for
human growth
hormone
Cell Transformation
 Transforming
Plant Cells
are also used to transfer DNA
into plant cells
 Some plant cells take up DNA on their
own when their cell walls are removed
 DNA can also be directly injected into
some plant cells
 The goal is to incorporate the DNA into
at least one of the chromosomes
 Plasmids
Plant Cell Transformation
Gene to be
transferred
Recombinant
plasmid
Cellular
DNA
Inside plant cell, Agrobacterium
inserts part of its DNA into host
cell chromosome
Transformed bacteria
introduce plasmids into
plant cells
Complete plant is
generated from
transformed cell
Vectors Transfer DNA
A plasmid is an
example of a vector
 A vector is any
means by which DNA
from another species
can be carried into a
host cell
 A rejoining of DNA
fragments is called

gene splicing
Gene
Splicing
Applying Genetic
Engineering

Transgenic organisms – any organism
that contains genes from another or many
other organisms
 Bacteria are primarily used to reproduce
substances important to the health
industry and to benefit humans
 They are considered transgenic
microorganisms and they are used to
grow cultures of human genes because
they reproduce rapidly and are easy to
work with
Transgenic Animals
Animals have been used to help scientists
study the effect of hormones and drugs
on the human body and also to culture
large amounts of useful human proteins
 They help us to :

 Study
genes and improve our food supply
 Study the effect of diseases in humans
 Develop drugs to resist certain diseases
 Produce proteins essential to human function
Transgenic Plants


Many of the plants and produce that you see daily in
the grocery store are genetically modified
Many “crops” contain transgenic plants that can be
resistant to disease and pests



This enables growers to spray generously without harming
the plant
Many of these chemicals stay on or in the plant as it makes
its way to your table 
Transgenic plants also have many of the dominant
traits that some of their “like” plants may contain in
different parts of the world
CLONING
A clone is an organism or sequence of
DNA that is genetically identical and
produced from a single cell
 If you were to clone yourself your clone
would look exactly like you and have your
exact and unique DNA sequence



An identical twin is an example of a clone
Cloning makes many advancements
possible in the realm of science but, the
question is should it be done?
Cloning of the First
Mammal
A donor cell is taken
from a sheep’s udder
Donor
Nucleus
These two cells are fused
using an electric shock.
Fused Cell
Egg Cell
An egg cell is taken
from an adult female
sheep.
Cloned Lamb
The nucleus of the
egg cell is removed.
Foster
Mother
Embryo
The embryo
develops normally
into a lamb—Dolly
The embryo is placed
in the uterus of a
foster mother.
The fused cell
begins dividing
normally.