Genetic Mutations

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Genetic Mutations
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Standards

• CLE 3210.4.6 Describe the connection between
  mutations and human genetic disorders.

Objectives

• Investigate the affect of mutations on protein
  production
• Differentiate between point mutations and
  chromosomal mutations.

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What is a gene mutation?

• Mutations are changes in genetic material
  changes in DNA code which means changes in a
  gene(s)
• In gene mutations, the DNA code will have one or
  more bases missing, added, or exchanged in a
  codon.

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How common are mutations?

• Mutations occurs at a frequency of about 1 in
  every 1 billion base pairs
• Everybody has about 6 mutations in each cell in
  their body!

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Does that mean I have a chance to become a super
hero/villian?
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If I have that many mutations, why dont I look
weird?

• Mutations are not always seen. The affected gene
  may still function.
• Mutations may be harmful.
• Mutations may be beneficial.
• Mutations may have no effect on the organism.

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How do mutationsaffect a population?

• Mutations are a major source of genetic variation
  in a population increasing biodiversity.
• Some variations may help them to survive better.

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Beneficial or Harmful?
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How are mutations inherited?

• Only mutations that occur in gametes are passed
  onto offspring.
• Mutations in body cells (somatic cells) only
  affect the organism in which they occur and are
  not passed on.

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Types of Gene Mutations

• Point mutation occurs when the base sequence of a
  codon is changed. (ex. GCA is changed to GAA)
• Chromosome mutations - Changes in the number or
  structure of chromosomes

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Types of Point Mutations

• Point mutation occurs when the base sequence of a
  codon is changed. (ex. GCA is changed to GAA)
• There are 3 types

• Substitution

• Also called frameshift mutations

• Deletion

• Insertion

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Substitution Mutations

• Normal DNA CGA TGC ATC

Alanine Threonine - stop
Mutated DNA CGA TGC TTC
Alanine Threonine - Lysine
What will happen to the amino acids?
This is a substitution mutation
The adenine was replaced with thymine
What has happened to the DNA?
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Substitution Mutations

• This is a substitution mutation.
• A single nitrogen base is substituted for another
  in a codon.
• It may or may not affect the amino acid or
  protein.

Normal DNA CGA TGC ATC
Alanine Threonine - stop
Mutated DNA CGA TGC TTC
Alanine Threonine - Lysine
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TRY THIS!

• On your note paper write
• The cat ate the rat
• Change one letter in the sentence to represent a
  substitution mutation.

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Think Pair - Share

• Why are we using 3 letter words?
• Share with your partner the substitution change
  that you made
• Can you still read your sentence fairly easily?
• How damaging is a substitution mutation?

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Analogy
The cat ate the
rat. SUBSTITUTION 1 Thc cat ate the rat. May
have little effect. You can still get the
overall idea. Like a typo on a
test. SUBSTITUTION 2 The hat ate the
rat. Changes the thought of the sentence. The
effect of the mutation depends on where the
substitution happens
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Insertion Mutations

• Normal DNA CGA TGC ATC

Alanine Threonine stop
Mutated DNA CGA TAG CAT C
Alanine Isoleucine Valine
This is an insertion mutation, also a type of
frameshift mutation.
What will happen to the amino acids?
An adenine was inserted thereby pushing all the
other bases over a frame.
What has happenedto the DNA?
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Insertion Mutations

• This is an insertion mutation.
• A nitrogen base is inserted/added to the
  sequence.
• It causes the triplet frames to shift.
• It always affects the amino acids and,
  consequently, the protein.

Normal DNA CGA TGC ATC
Alanine Threonine - stop
Mutated DNA CGA TAG CAT C
Alanine Leucine - Valine
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Think pair - share

• Predict the effect an insertion mutation cause to
  our sentence
• THE CAT ATE THE RAT

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TRY THIS!

• On your notebook paper write
• The cat ate the rat.
• Insert a letter into any word above.
• Rewrite the sentence . Each word must have only
  3 letters to represent the codon.
• What were the effects of the insertion?

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Analogy The cat ate the rat. Insertion The cca
tat eth era t. Inserting the c causes a
FRAMESHIFT THE SENTENCE NO LONGER MAKES SENSE!!
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Think pair - share

• Where in the gene sequence would an insertion
  mutation cause the most damage to the DNA code?
• At the beginning of the gene sequence

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Lets examine the effect of location

• THE CAT ATE THE RAT
• INSERTION 1
• THE CAT ATE THA ERA T
• Would any of the codons code correctly?
• INSERTION 2
• TAH ECA TAT ETH ERA T
• Would any of these codons code correctly?

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Deletion Mutations

• Normal DNA CGA TGC ATC

Alanine Threonine stop
Mutated DNA CGA TCA- TC
Alanine Serine
What will happen to the amino acids?
A guanine was deleted, thereby pushing all the
bases down a frame.
This is called a deletion mutation, also a type
of frameshift mutation.
What has happenedto the DNA?
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Deletion Mutations

• This is a deletion mutation.
• A nitrogen base is deleted/removed from the
  sequence.
• It causes the triplet frames to shift.
• It always affects the amino acids and,
  consequently, the protein.

Normal DNA CGA TGC ATC
Alanine Threonine stop
Mutated DNA CGA TCA- TC
Alanine Serine
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TRY THIS!

• Write the sentence on your paper
• The cat ate the rat.
• Delete one letter from any word.
• Rewrite the sentence. Remember each word can
  only have 3 letters.

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Analogy DELETION The cat ate the rat. Thc ata tet
her at FRAMESHIFT The sentence no longer makes
sense!! Deletions can have huge effects.
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Standards

• CLE 3210.4.6 Describe the connection between
  mutations and human genetic disorders.

Objectives

• Investigate the affect of mutations on protein
  production
• Differentiate between point mutations and
  chromosomal mutations.

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Think pair - share

• Which type of mutation would have the least
  damaging affect on an organism?

• Substitution has the least affect because it
  changes only one amino acid or it may change no
  amino acid.

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• An example of a substitution mutation is sickle
  cell anemia

• Only one amino acid changes in the hemoglobin.
• The hemoglobin still functions but it folds
  differently changing the shape of the rbc.

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Think pair - share

• Which type(s) of mutation would have the most
  affect on an organism?

• Insertion and deletion mutations have the most
  effect on an organism because they affect many
  amino acids and consequently the whole protein.

Normal DNA CGA TGC ATC
Alanine Threonine stop
Mutated DNA CGA TCA- TC
Alanine Serine
Mutated DNA CGA TAG CAT C
Alanine Leucine - Valine
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An example of a frameshift mutation disorder is
Tay Sachs disease.

• Children born with this disorder cannot make an
  enzyme that is critical in breaking down fat and
  toxic substances in the brain.
• The disease is terminal. Most will die before age
  4.

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Think pair - share

• In which cells would a gene mutation have the
  greatest affect on an organism?

Egg being fertilized

• When it is inherited from the gametes or
  develops early in embryonic development (in stem
  cells or first few days).

Four cell Zygote
Embryo
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Mutagens

• What causes mutations?
• natural errors during replication
• an environmental mutagen/carcinogen
• What is a mutagen (carcinogen)?
• something that causes the DNA code to change
  (mutate) x-ray, chemicals, UV light, radiation,
  etc
• What happens to a person who has a mutation?

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Gene Mutations Activity

• Complete the worksheet

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Chromosomal Mutationsthink pair - share

• How do you think we could mutate a chromosome?
• List at least 3 ways

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Chromosomal Mutations

• Changes in the number or structure of chromosomes
• Deletions
• Duplication
• Inversion
• Translocation
• Nondisjunction

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Deletions

• removal of a gene and/or entire chromosome

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Duplication

• repeat of a gene or chromosome

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Inversion

• gene sequences are switched on the chromosome

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Translocation

• part of one chromosome breaks off and reattaches
  to a non-homologous chromosome

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Think - pair - share

• Compare and contrast translocation with crossing
  over
• How are they similar?
• How are they different?

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Non-disjunction

• A chromosome fails to separate from its homologue
  during meiosis

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Downs Syndrome

• Result of nondisjunction of the chromosomes at
  pair 21

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Homework

• Chromosome Mutation activity

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Standards

• CLE 3210.4.6 Describe the connection between
  mutations and human genetic disorders.

Objectives (DID WE)

• Investigate the affect of mutations on protein
  production
• Differentiate between point mutations and
  chromosomal mutations.

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Exit Ticket

• How do mutations affect the production of a
  protein?