Transcript SB2. Students will analyze how biological traits are passed on to

SB2. Students will analyze how
biological traits are passed on to
successive generations
d. Describe the relationships
between changes in DNA and
potential appearance of new traits
What are some mutagenic factors
and what effects do they have on
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LEQ#3: What are some
mutagenic factors and what
effects do they have on DNA?
What are some mutagenic factors
and what effects do they have on
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Vocabulary to Know:
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Mutagenic Factor
Mutation
Mutagen
Pesticides
Herbicides
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Radiation
X-Rays/ UV rays
Chemicals
Viruses
Phenotype
What are some mutagenic factors
and what effects do they have on
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Mutagenic Factors
• Agents in the environment that can
change DNA are called mutagenic factors
– Also called mutagens
What are some mutagenic factors
and what effects do they have on
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Mutagenic Factors
• Examples
– UV rays in sunlight (Natural factor)
– Radiation (X-rays and Nuclear)
– Industrial Chemicals
• Pesticides: Chemical substance used to against any pests.
• Herbicides: Chemical substance used to kill plants
• Cigarettes
– Biological agent
• Antimicrobial or disinfectant
• Viruses
What are some mutagenic factors
and what effects do they have on
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What are some mutagenic factors
and what effects do they have on
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Effects on DNA
• Mutagenic factors can cause mutations
– Change in the DNA that affects the sequence of
nitrogen bases in the DNA
• Changes that occur in the DNA sequence may
or may not lead to changes in an organism
What are some mutagenic factors
and what effects do they have on
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What is a mutation?
• Change in an organisms DNA is called a
mutation.
• Not uncommon
• May or may not affect the phenotype of an
organism
– Physical characteristics
• May or may not have an impact of
offspring
What are some mutagenic factors
and what effects do they have on
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Effects on organism
• Human body has DNA repair enzymes that
help find and fix mutations
• Although, sometimes these enzymes don’t
work and the mutation is not fixed
– The DNA site for the production of that
enzyme has been damaged by the mutation
• Errors or mutations can build up overtime
and eventually effect how the cell works.
– Mutations are a significant cause of aging
What are some mutagenic factors
and what effects do they have on
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Explain how mutagens can cause
genetic mutations in spite of your
body’s DNA repair enzymes.
What are some mutagenic factors
and what effects do they have on
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Answer
• Mutagens may produce so much damage
that the repair enzymes cannot keep up
with the repairs.
What are some mutagenic factors
and what effects do they have on
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LEQ#4: What are the types of
alterations that can occur
during replication?
What are some mutagenic factors
and what effects do they have on
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Vocabulary to Know:
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Point mutation
Framshift mutation
Gene mutation
Chromosomal
mutation
• Substitutions
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Deletion
Duplication
Inversion
Translocation
Nondisjunction
Trisomy
What are some mutagenic factors
and what effects do they have on
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Mutations
• Two main types:
– Gene Mutation
• Mutation that causes a change in a
single gene
– Chromosomal Mutation
• Mutation that involves the entire
chromosome
• Both can be caused by nature, random
events, or environmental factors
What are some mutagenic factors
and what effects do they have on
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Gene Mutations
• Error in the sequence of nitrogen bases in
a single gene
– Remember: Codon (sequence of 3 nitrogen
bases) corresponds to a particular amino acid
• Two types of Gene Mutations:
– Point mutation
– Frame shift mutation
What are some mutagenic factors
and what effects do they have on
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Gene Mutations
• Error in the sequence of nitrogen bases in
a single gene
– Remember: Codon (sequence of 3 nitrogen
bases) corresponds to a particular amino acid
• Two types of Gene Mutations:
– Point mutation
– Frame shift mutation
What are some mutagenic factors
and what effects do they have on
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Gene Mutation
Point Mutation
• Change in a single base is called a point mutation
• Each of these words represents different amino acid.
THE CAT ATE THE RAT
• Now what would happen if you changed one letter?
THE CAT ATE THE BAT
• Still makes sense but the meaning is different
– Effects are usually minimal if any at all
• Example: Sickle Cell
– GAG codon is changed to GTG
– Inserts wrong amino acid
What are some mutagenic factors
and what effects do they have on
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Gene Mutation
Frameshift Mutation
• Base is added/deleted is called a Frameshift
mutation
THE CAT ATE THE RAT
Deleted one base: C
THE ATA TET HER AT_
Added one base: C
THE CCA TAT ETH ERA T
• The statement makes no sense and the
meaning is completely different
– Effects much more severe than a point mutation
– Codon for different amino acid
What are some mutagenic factors
and what effects do they have on
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Wasting Syndrome
• Gene mutation that
results in the mutated
form of myostatin
protein.
• Leads to
overproduction of
muscle tissue
• Often seen in Belgian
Blue and
Piedmontese breeds
of cattle
What are some mutagenic factors
and what effects do they have on
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Explain why Frameshift
mutations have a greater effect
than do Point Mutations.
What are some mutagenic factors
and what effects do they have on
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Answer
• Point mutations typically affect only one
codon (unless they create a premature
stop codon).
• A frame shift mutation affects all the
codons in a gene that follow it.
What are some mutagenic factors
and what effects do they have on
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Chromosomal Mutations
• Changes in the number of chromosomes
or their structure
• Occur: Chromosomes fail to separate
correctly during gamete production
– Nondisjunction
• Lead to abnormalities in offspring
– Example: Cyclopia
• 3 (trisomy) chromosomes of chromosome 13-15
or 17-18
What are some mutagenic factors
and what effects do they have on
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What are some mutagenic factors
and what effects do they have on
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Cyclopia
• Two eyes within one
orbit
• Proboscis-like
appendage above the
eye
• Low-set or missing ears
• Missing facial bones
• Congenital heart
disease
• Do not survive
What are some mutagenic factors
and what effects do they have on
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Chromosomal Mutations
• 4 types of mutations
– Deletion
– Duplication
– Inversion
– Translocation
What are some mutagenic factors
and what effects do they have on
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Chromosomal Mutation
Deletion
• Occurs when part of a chromosomes
breaks off during mitosis/meiosis
• Serious mutation that often causes death
of the organism
What are some mutagenic factors
and what effects do they have on
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Chromosome Mutation
Duplication
• Occurs when a section of a chromosomes
is repeated
• May cause genes to not function properly
• Can also lead to developmental and
physical disabilities
What are some mutagenic factors
and what effects do they have on
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How could a mutated gene
produce a shorter protein than
that produced by the normal
gene?
What are some mutagenic factors
and what effects do they have on
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Answer
A frame shift or a point mutation may have
changed one of the codons to a stop
codon
What are some mutagenic factors
and what effects do they have on
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Chromosomal mutation
Inversion
• Occurs when a section of a chromosome
breaks off, changes direction, and
recombines to the same chromosome
• Usually no serious effects
• Genes are still intact and present on
correct chromosome
What are some mutagenic factors
and what effects do they have on
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Chromosomal Mutation
Translocation
• Piece of chromosome breaks off one
chromosome and combines with a
different chromosome
• Causes serious physical and
developmental disabilities
What are some mutagenic factors
and what effects do they have on
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Translocation
• Results in miscarriage of zygote usually
• Produce gametes with wrong number of
chromosomes
• Usually harmless but can cause cancers
(leukemia), and infertility
What are some mutagenic factors
and what effects do they have on
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Did you know…
• Mutations can occur in
all types of
organisms…even the
human race.
• One mutation that is
very unlikely to be
seen is multiple toes
and fingers.
• Doctors usually
remove extra digits at
birth.
What are some mutagenic factors
and what effects do they have on
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LEQ#5: What relationships
exist between mutations and
the potential appearance of
new traits?
What are some mutagenic factors
and what effects do they have on
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Vocabulary to Know:
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Germ line mutation
Somatic Mutation
Sterile
Inherited
Meiosis
Beneficial mutation
Lethal Mutation
Silent mutation
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Turners syndrome
Down syndrome
Klinefelters syndrome
Cystic fibrosis
Cancer
Gametes
Harmful mutation
Intron
What are some mutagenic factors
and what effects do they have on
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Consequences of Mutations
• Depend on the type of cell the DNA
mutation occurs in
• Can occur in two types of cells
– Somatic (body cell)
– Germ line (gametes: sperm/egg)
What are some mutagenic factors
and what effects do they have on
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Somatic Mutation
• Are NOT passed down to offspring
• Causes:
– Random natural causes
– Environmental factors: radiation, x-rays,
sunlight
– Chemical: cigarettes, cleaners, pesticides
• Often lead to cancer
What are some mutagenic factors
and what effects do they have on
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Germ Line Mutations
• Mutations can be passed down to offspring
(inherited)
• Usually occur during Meiosis
– Type of cell division the produces gametes in sexually
reproducing organisms
• Mutations in germ line affect the phenotype of
the offspring.
• Many are so severe that offspring do not
develop properly and die before they can
reproduce or are sterile
– Incapable of producing offspring
What are some mutagenic factors
and what effects do they have on
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Appearance of new traits
• Impact on phenotype of organism
– Silent mutation
– Harmful mutation
– Lethal mutation
– Beneficial mutation
• Impact on offspring
What are some mutagenic factors
and what effects do they have on
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Impact on Phenotype
• Many gene mutations do not affect an
organisms phenotype.
• Mutation that does not affect the resulting
protein is called a silent mutation.
• Mutation that occurs on the noncoding
region (intron) may not affect the encoded
protein at all.
– Segment of gene that does not code for an
amino acid
What are some mutagenic factors
and what effects do they have on
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Impact on Phenotype
• Chromosomal mutations affect a lot of
genes and tend to have a big effect on an
organism
• Mutation that alters a important protein
and affects its function is called a harmful
mutation
What are some mutagenic factors
and what effects do they have on
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Klinefelters Syndrome
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XXY (47 Chromosomes)
Extra sex chromosome
Sterile
increase breast tissue,
decrease in
testosterone
Greatly reduced male
genitalia
Some breast production
Wide curvy hips
No sperm production &
no sex drive
Sterile
What are some mutagenic factors
and what effects do they have on
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Down Syndrome
• Extra copy of
chromosome 21 (47
chromosomes)
• Broad short head
• Malformed ears
• Mental retardation
• Protruding tongue
when mouth is open
• Impairment of
cognitive and physical
development
What are some mutagenic factors
and what effects do they have on
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Turner’s syndrome
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X0 ( 45 Chromosomes)
only one female sex chromosome
Short stature
Wide-spaced
underdeveloped nipples
Webbed neck
Swelling of hands & feet
low hairline
Sterile
What are some mutagenic factors
and what effects do they have on
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Lethal Mutation
• Mutations that lead to the death of an
organism are considered to be lethal
mutations
What are some mutagenic factors
and what effects do they have on
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Patau’s Syndrome
• Trisomy
chromosomes 13-15
• Cleft lip and palate
• Bone defects on skull
• Large bulbous nose
• Congenital heart
disease
• Majority die within a
year
What are some mutagenic factors
and what effects do they have on
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Edward’s Syndrome
• Trisomy on
chromosomes 17-18
• Small head
• Ears deformed
• Cleft palate
• Severe retardation
• Majority die within a
year
What are some mutagenic factors
and what effects do they have on
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Impact on the Phenotype
• A very small percentage of all mutations actually
have a positive effect these are called beneficial
mutations.
• These mutations lead to new versions of
proteins that help an organism and its future
generations better adapt to changes in their
environment.
• Example:
– Deletion of CCR5 gene leads to HIV resistance
– Found in European descent
– Believe to be a result of survivors of the bubonic
plague or small pox
What are some mutagenic factors
and what effects do they have on
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Some genetic mutations are
associated with increased risk for a
particular disease. Tests exist for
some of these genes. What might
be the advantages and
disadvantages of being tested
What are some mutagenic factors
and what effects do they have on
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Answer
• Advantage:
– You would know what symptoms to look for
– You would be able to prepare for treatment
• Disadvantage:
– There may be no cure for the disease
– Simply having the gene may not mean that
getting the disease is inevitable
What are some mutagenic factors
and what effects do they have on
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