Download Genetic Mutations - Velma Jackson High

Genetic Mutations
“The Tale of the Incorrect Code”
What are Mutations?
 Mutations are mistakes in the DNA sequencing
 Can be acquired during an individuals life or passed from
parent to child.
 Mistakes affect genetic information that is passed to
offspring
 Some mistakes are so small they are never noticed, others
cause severe problems
o Remember: amino acids make up polypeptide
chains. Polypeptide chains make up proteins.
Proteins are a vital component of living materials
and carry out vital cellular processes.
Mutations During Mitosis
 MOST mutations occur when DNA is being copied
 Cells have processes to help it catch mistakes
 When mistakes aren’t repaired, it can lead to cellular
malfunctions
 Affects the cell that produced the mistake
 Mistakes in somatic cells affect the individual ONLY
Mutations During Meiosis
 Mutations can be passed on to offspring
 Becomes a part of the offspring’s DNA in almost every
cell
 Can be passed on to the next generation
External Causes of Mutations
 Mutagen:
 External things that can change DNA, such as radiation, xrays, or chemicals (tobacco, asbestos, benzene, etc.)
 Common result is cancer
 Ultraviolet radiation can “switch around” base pairs in DNA and
cause skin cancer.
 Carcinogen:
 a mutagen that is directly involved in causing cancer
Let’s Practice
1. Which of these would be LEAST likely to cause a gene
mutation?
A. Exposure to x-ray radiation
B. Exposure to ultraviolet radiation
C. Exposure to tobacco smoke
D. Exposure to loud noises
2. A harmful chemical is inhaled into the lungs and causes a
mutation in a lung cell. Which of the following is NOT likely
to occur?
A. The mutation results in lung cancer
B. The mutation causes the lung cell to function improperly
C. The mutation causes the lung cell to die
D. The mutation is passed on to a son or daughter
Examine the Effects of a Mutation
 Normal DNA: TAC ACA CGA
 RNA: __ __ __
__ __ __
__ __ __
 PROTEIN: ____ ____ ____
 Mutated DNA: TAC ACT CGA
 RNA: __ __ __
__ __ __ __ __ __
 PROTEIN: ____ ____ ____
Did you get it?
Types of mutations
 Gene Mutations: mutation that changes one gene
 Chromosomal Mutations: mutation caused when a
chromosome or part of a chromosome is duplicated,
deleted, or attached incorrectly
Gene Mutations
Point Mutation
Frameshift Mutation
 Gene mutation that
occurs if a nucleotide is
added, deleted, or
substituted in the
nucleotide sequence
 Another name for when a
single nucleotide is
added or deleted
Substitution
 Switch 1 nucleotide for another
Addition/Deletion = Frameshift
 Addition: add a new nucleotide
 Deletion: remove a nucleotide
 Both result in a frame shift to the reading frame
Common Inherited Gene Mutation
Disorders
Autosomal Recessive Disorders (defective gene from both parents)
 Sickle Cell Anemia: single substitution
 Tay-Sachs disease: Frameshift
 Cystic Fibrosis
Sex-linked Disorders
 Red-Green Colorblindness
 Hemophilia
Chromosomal Mutations
 The structure or numbers of chromosomes change.
 Structure changes if part of a chromosome is broken off or
lost during mitosis or meiosis.
Can pass on defective chromosomes, or can cause too many/few
chromosomes to be passed on.
 Duplication
 Deletion
 Inversion
 translocation
Common Chromosome Mutation
Disorder
Down’s Syndrome (trisomy 21)
 Caused by nondisjunction of chromosome 21, causing
the individual to have 3 copies of chromosome 21
instead of 2
 NONDISJUNCTION: chromosomes do not separate correctly
during meiotic division causing gamete to have an extra or
missing chromosome.
Fertilization results in some form of genetic disorder
Chromosomal Mutations
1.
Duplication: make and extra copy of the gene
2.
Deletion: remove a gene
3.
Translocation: a gene moves another chromosome
4.
Inversion: the genes reattach backward
1.
Paracentric: occurs on same side of the centromere
2.
Pericentric: occurs across the centromere
Self Check!
Karyotype
 Map of chromosomes
that can be used to see if
one or more
chromosomes are
misshapen.
 Chromosomes are
easier to see if stained
during metaphase
Future Doctors of the World
Sickle Cell Anemia
 1 in 12 African Americans suffer from this disease
 A substitution point mutation occurred in the DNA. Results in the
addition of Valine instead of Glutamic Acid in the amino acid
sequence. This causes the Hemoglobin protein to be misshaped.
Sickle Cell Anemia
 Hemoglobin is located in your red blood cells
 It carries oxygen to all of the cells of your body
Sickle Cell Anemia
 The misshaped protein causes the round, red blood cells to
become sickled in shape
 They cannot carry as much oxygen and they break very easily,
clogging the arteries
Tay-Sachs
 Enzyme needed to break down a certain type of fat is
defective
 progressively destroys nerve cells (neurons) in the brain
and spinal cord.
 infants lose motor skills such as turning over, sitting, and
crawling.
 They also develop an exaggerated startle reaction to loud
noises. As the disease progresses, children with Tay-Sachs
disease experience seizures, vision and hearing loss,
intellectual disability, and paralysis. An eye abnormality
called a cherry-red spot, which can be identified with an eye
examination, is characteristic of this disorder. Children with
this severe infantile form of Tay-Sachs disease usually live
only into early childhood.
Cystic Fibrosis
 CF is most common
among people of Central
and Northern European
ancestry
 abnormal transport of
chloride and sodium
across an epithelium,
leading to thick, viscous
secretions
Down’s Syndrome
 typically associated with
physical growth delays, a
particular set of facial
characteristics and a
severe degree of
intellectual disability.
 The average full-scale
IQ of young adults with
Down syndrome is
around 50
 (70 and below is
defined as the cut-off
for intellectual
disability), whereas
young adult controls
have an average IQ of
100
Let’s Practice
DNA Technology
 Due to improvements in
technology a new branch
of science, Molecular
genetics, has been
created.
 Molecular Genetics is the
study of DNA
DNA Extraction and Gel
Electrophoresis
 DNA extraction is the
process used to separate
DNA from the rest of the
cell.
 DNA must then be cut
into smaller pieces to
make them easier to
study
 DNA is cut by using
restriction enzymes and
separated by gel
electrophoresis
Restriction Enzymes
 Cut DNA into smaller pieces
Gel Electrophoresis
 After DNA is cut, it is separated by length in a gel
 DNA is attracted to positive side of the battery
 Smaller fragments move faster
DNA fingerprinting
 Each person’s DNA will separate differently with gel
electrophoresis
 Can be used to determine the father of an individual
It’s the Maury Show!!!
When it
comes to
the puppy in
question,
Dog #
_______
you ARE the
father!!!
Recombinant DNA
 Made by taking short pieces of DNA from one organisn
and joining it it the DNA of a completely different
organism.
 Once it is made, it is placed back into a living cell in a
process called transformation.
 Transformation is useful in medicine because scientist can
transform bacteria to have human DNA in them.
 i.e. used to produce insulin
Recombinant DNA
 Taking DNA from 2 different organisms and re-combining them
together
 Gene splicing
Transformation
 Recombinant DNA is put into cells (usually bacteria) to make human
hormones
 Insulin
How Does it Work?
 Bacterial cells contain a plasmid (small circular pieces of
DNA).
 The gene for human insulin is curt from DNA with the
same restriction enzyme used to cut bacterial plasmids
 The human DNA piece is placed in the bacterial plasmid
and placed back into the bacteria cell
 Bacteria reproduce rapidly, making multiple copies of the
insulin producing gene
 The gene is extracted and used to make medicine
Transgenic Organisms
Organism that contains genes from another organism
Benefits
Disadvantages
 Transgenic cows grow
larger, faster, and with less
fatty beef
 Cross pollination with
wild plants could result in
uncontrollable growth
 Transgenic plants are more
resistant to pests, disease,
insecticides
 Could cause allergies or
other medical problems
in people who eat it
Cloning
 Transferring genetic material of a donor cell into an egg
cell that has had it’s nucleus removed
 The egg is then stimulated by chemicals or electricity to
cause it to divide
 Next, it is implanted into the uterus of a female until further
development until birth
 The cloned organism is genetically identical to the original
or parent organism
 May be used to save endangered species.
Cloning
 Putting DNA into an egg cell
 The egg cell splits by mitosis to make an identical copy