Post on 16-Dec-2015
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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.
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.
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!
If I have that many mutations, why don’t 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.
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.
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.
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
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:
Also called frameshift mutations
•Substitution
•Deletion
•Insertion
What will happen to the amino acids?
Substitution Mutations
Normal DNA: CGA – TGC – ATC
Mutated DNA: CGA – TGC – TTC
Alanine – Threonine - stop
Alanine – Threonine - Lysine
This is a substitution mutation
The adenine was replaced with thymineWhat has happened to
the DNA?
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.
Mutated DNA: CGA – TGC – TTC
Alanine – Threonine - Lysine
Normal DNA: CGA – TGC – ATC
Alanine – Threonine - stop
TRY THIS!
• On your note paper write:The cat ate the rat
• Change one letter in the sentence to represent a substitution mutation.
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?
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
This is an insertion mutation, also a type of
frameshift mutation.
Insertion Mutations
Normal DNA: CGA – TGC – ATC
Mutated DNA: CGA – TAG – CAT – C
Alanine – Threonine – stop
Alanine – Isoleucine – Valine
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?
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.
Mutated DNA: CGA – TAG – CAT – CAlanine – Leucine - Valine
Normal DNA: CGA – TGC – ATC Alanine – Threonine - stop
Think – pair - share
• Predict the effect an insertion mutation cause to our sentence:
THE CAT ATE THE RAT
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?
AnalogyThe cat ate the rat.
Insertion
The cca tat eth era t.
Inserting the c causes a
FRAMESHIFT
THE SENTENCE NO LONGER MAKES SENSE!!
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
Let’s examine the effect of locationTHE 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?
What will happen to the amino acids?
Mutated DNA: CGA – TCA- TC
A guanine was deleted, thereby pushing all the bases down a frame.
Alanine – Threonine – stop
Alanine – Serine
Deletion Mutations
Normal DNA: CGA – TGC – ATC
This is called a deletion mutation, also a type of
frameshift mutation.
What has happenedto the DNA?
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.
Mutated DNA: CGA – TCA- TCAlanine – Threonine – stop
Alanine – Serine
Normal DNA: CGA – TGC – ATC
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.
AnalogyDELETION
The cat ate the rat.
Thc ata tet her at
FRAMESHIFT
The sentence no longer makes sense!! Deletions can have huge
effects.
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.
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.
Mutated DNA: CGA – TGC – ATTAlanine – Threonine - stop
Normal DNA: CGA – TGC – ATC Alanine – Threonine - stop
Mutated DNA: CGA – TGC – ATGAlanine – Threonine - Tyrosine
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.
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.
Mutated DNA: CGA – TCA- TCAlanine – Threonine – stop
Alanine – Serine
Normal DNA: CGA – TGC – ATC
Mutated DNA: CGA – TAG – CAT – CAlanine – Leucine - Valine
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.
Think – pair - share
• In which cells would a gene mutation have the greatest affect on an organism?
• When it is inherited from the gametes or develops early in embryonic development (in stem cells or first few days). Four cell Zygote
Embryo
Egg being fertilized
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?
Chromosomal Mutationsthink – pair - share
• How do you think we could mutate a chromosome?
• List at least 3 ways
Chromosomal Mutations• Changes in the
number or structure of chromosomes
• Deletions
• Duplication
• Inversion
• Translocation
• Nondisjunction
Think - pair - share
• Compare and contrast translocation with crossing – over–How are they similar?–How are they different?
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.