3C3 Lesson - Gene Mutations

3C3 Lesson - Gene Mutations

​	​Transcription	​Translation
​Location	​1	3​
Product​	​2	4​

​DNA Sequence	​TAC	​GAT	​ACT
mRNA Sequence​	​5	6​	7​
Amino Acid Sequence​	​8	9​	10​

​3C Review

​	​Transcription	​Translation
​Location	nucleus	ribosome
Product​	​mRNA	protein

​DNA Sequence	​TAC	​GAT	​ACT
mRNA Sequence​	AUG	CUA	UGA
Amino Acid Sequence​	Met	Leu	Stop

​3C Review

Mutations are mistakes in DNA sequencing
Gene Mutations

• Mistakes in DNA sequencing during DNA replication

  • DNA replication - when when most gene mutations occur

  • main source of genetic variation

• Somatic mutations - acquired mutations that occur to body cells

  • may lead to cancer

• Germ-line mutations - inheritable mutations that occur to gametes

  • in ovaries (egg) or testes (sperm) - meiosis

  • These mutations can be passed to the next generation.

  • These mutations become a part of the all of offspring’s DNA in almost every cell.

• Sickle cell anemia - red blood cells are rigid and crescent-shaped, leading to blockages in blood flow and causing pain and organ damage

• Tay-Sachs - accumulation of fat in the brain - death by age of 5

• Cystic fibrosis - causes thick, sticky mucus to build up in the lungs and digestive system, leading to breathing and digestive problems

• Hemophilia - impairs blood clotting, resulting in prolonged bleeding

• Muscular Dystrophy- progressive muscle degeneration and weakness

• PKU - phenylalanine buildup in brain causing brain damage

​Examples of Gene Mutations

• DNA is the genetic material of a cell

• DNA contains the instructions to make proteins in the order of nucleotides (Gene)

• DNA has the instructions to make proteins

• Change the order, change the protein

• The order of nucleotides in DNA determines the order of amino acids in a protein.

• Changing the order of amino acids will change the shape of the protein that is made.

• So, a change in the DNA sequence (mutation) could change the protein that is made.

• The protein may not do its job correctly.

​A proteins shape determines its function.

Multiple Choice

Cystic fibrosis is most commonly caused when a gene on chromosome 7 is missing three base pairs (nucleotides / letters) that code for one amino acid in a protein.

How would you expect this missing amino acid to affect the protein?

• The protein would be abnormally shaped

• The protein would be too long

• The protein would be more easily broken down by enzymes

• The protein would be produced in smaller amounts

Extra, missing, or exchanged nucleotides

Point Mutation

• only kind is substitution

• changes only ONE amino acid in a sequence

Frameshift Mutations

• Deletion

• Insertion

• changes ALL of the amino acids after the mutation

Substitution

• one nucleotide replaces another

Insertion

• a nucleotide is added

Deletion

• a nucleotide is removed

​

​

​

Match

Match the following

• one nucleotide replaces another

• a nucleotide is added to the sequence

• a nucleotide is removed from the sequence

substitution

insertion

deletion

• substitution

• insertion

• deletion

Substitution

• one nucleotide replaces another

• Point Mutation

• TTT-AAA-CCC

• TAT-AAA-CCC

• Sickle Cell Anemia

Insertion

• a nucleotide is added

• Frameshift mutation

• shifts frame to the right

• TTT-AAA-CCC

• TAT-TAA-ACC-C

• Tay-Sachs

Deletion

• a nucleotide is removed

• Frameshift mutation

• shifts frame to the left

• TTT-AAA-CCC

• TTA-AAC-CC

• Cystic Fibrosis

​

​

​

Multiple Choice

wildtype DNA segment is: TTA-CGC-AAG

mutated DNA segment is: TTA-CGC-AAC.

This is an example of ___ mutation.

<COUNT!>

• Substitution

• Insertion

• Inversion

Multiple Choice

wildtype DNA: CAT-GAT-CCA

mutated DNA: CAT-TGA-TCC-A

What mutation occurred?

<COUNT!>

• deletion

• substitution

• insertion

Multiple Choice

wildtype DNA segment : TTA-CGC-AAG

mutated DNA segment: TTC-GCA-AG.

What kind of mutation has occurred?

<COUNT!>

• Substitution

• Deletion

• Insertion

3C3 Effects of Mutations

• Mild - not noticeable

• Severe - causes disease and death

• Beneficial - leads to an adaptation that helps an organism survive a changing environment

  • Main source of genetic variation

Match

Match the following

• amino acid sequence does not change

• a new amino acid is added to the sequence

• a STOP codon is added to the sequence

silent

missense

nonsense

• silent

• missense

• nonsense

Silent Point Mutation

• does not change the amino acid sequence - does not change protein

Missense

• adds one or more amino acids to the sequence - changes protein

Nonsense

• adds a STOP codon to the sequence - removes the rest of the amino acids in the sequence - changes protein

Silent

• does not change the amino acid sequence

• does not change protein made

Missense

• adds one or more amino acids to the sequence

• changes amino acid sequence

Nonsense

• adds a STOP codon to the sequence

• ends amino acid sequence early

Multiple Choice

A substitution mutation results in the formation of a STOP codon in the middle of a gene sequence.

How will this mutation affect the protein being formed?

• The protein will contain fewer amino acids than it should

• The protein will become cancerous

• The protein will have the correct shape but will not have the correct function

• The protein will not be affected by this type of mutation

Mutations and mRNA Codon Chart

• Uses mRNA

• Change DNA to mRNA

• Use mRNA code to find the amino acid sequence (protein/polypeptide)

DNA = TAC-GGG-CCC
mRNA = AUG-CCC-GGG
Amino acid
sequence
(protein) = Met-Pro-Gly

​

​Substitution 1	​Wild Type (Normal)	​Substitution Mutation
​DNA Sequence	​GTA-CAG-ATA	GTA-CAG-AT​G
mRNA Codon Sequence​	​CAU-GUC-UAU	​
Amino Acid Sequence​	His - Val - Tyr​	​
​Effect	-- -- -- -- --​	​

No change in DNA sequence length

​T H E|C A T|A T E | T H E |F A T| R A T (G replaces C)
T H E|G A T|A T E | T H E |F A T| R A T
Affects only one amino acid

​Substitution 1	​Wild Type (Normal)	​Substitution Mutation
​DNA Sequence	​GTA-CAG-ATA	GTA-CAG-ATG
mRNA Codon Sequence​	​CAU-GUC-UAU	CAU-GUC-UAC​
Amino Acid Sequence​	His - Val - Tyr​	​His - Val - Tyr
​Effect	-- -- -- -- --​	Silent​

​

​Substitution 2	​Wild Type (Normal)	​Substitution Mutation
​DNA Sequence	​GTA-CAG-ATA	​GTA-CAG-ATC
mRNA Codon Sequence​	​CAU-GUC-UAU	​
Amino Acid Sequence​	His - Val - Tyr​	​
​Effect	-- -- -- -- --​	​

​Substitution 2	​Wild Type (Normal)	​Substitution Mutation
​DNA Sequence	​GTA-CAG-ATA	​GTA-CAG-ATC
mRNA Codon Sequence​	​CAU-GUC-UAU	CAU-GUC-UAG​
Amino Acid Sequence​	His - Val - Tyr​	His - Val - STOP
​Effect	-- -- -- -- --​	Nonsense

​

​Insertion	​Wild Type (Normal)	​Insertion Mutation
​DNA Sequence	​GTA-CAG-ATC	GTA-CAG-
mRNA Codon Sequence​	​CAU-GUC-UAG	​
Amino Acid Sequence​	His - Val - Tyr​	​
​Effect	-- -- -- -- --​	​

​DNA sequence is longer

​Insertion	​Wild Type (Normal)	​Insertion Mutation
​DNA Sequence	​GTA-CAG-ATG	GTA-CAG-GAT-C
mRNA Codon Sequence​	​CAU-GUC-UAC	CAU-GUC-CUA-G
Amino Acid Sequence​	His - Val - Tyr​	His - Val - Leu
​Effect	-- -- -- -- --​	​Missense

​

​Deletion	​Wild Type (Normal)	​Deletion Mutation
​DNA Sequence	​GTA-CAG-ATG	​GTA-AGA-TA
mRNA Codon Sequence​	​CAU-GUC-UAC	​
Amino Acid Sequence​	His - Val - Tyr​	​
​Effect	-- -- -- -- --​	​

​DNA sequence is shorter

Deletion​	​Wild Type (Normal)	​Deletion Mutation
​DNA Sequence	​GTA-CAG-ATC	​GTA-AGA-TA
mRNA Codon Sequence​	​CAU-GUC-UAG	CAU-UCU-AU
Amino Acid Sequence​	His - Val - Tyr​	​His - Ser
​Effect	-- -- -- -- --​	Missense​

​

Practice Questions

Dropdown

DNA sequence: TAT-AGT-CTT

Mutation: TAT-AGG-TCT-T

This mutation is caused by a(n) ​

Select answer

of a nucleotide. .

This is a

Select answer

mutation.

Dropdown

DNA sequence: TAT-AGT-CTT

Mutation: TAT-AGG-CTT

This mutation is caused by a(n) ​
Select answer
of a nucleotide. .

This is a
Select answer
mutation.

Dropdown

DNA sequence: TAT-ATG-TCT

Mutation: TAT-ATT-CT

This mutation is caused by a(n) ​
Select answer
of a nucleotide. .

This is a
Select answer
mutation.

Dropdown

DNA sequence: TAT-ATG-CTT

Mutation: TAT-ATC-CTT

This mutation is caused by a(n) ​
Select answer
of a nucleotide. .

This is a
Select answer
mutation.

Labelling

Label the kinds of gene mutations.

Drag labels to their correct position on the image

Substitution

Insertion

Deletion

Multiple Choice

What kind of mutation occurred?

[change DNA to mRNA, then look on codon chart]

DNA sequence: TAT-AGT-CTT

Mutation: TAT-AGG-TCT-T

• Missense
• Nonsense
• Silent

Multiple Choice

Look at the two nucleotide sequences for a section of DNA given.

What type is the result of this mutation?

• silent - did not change the amino acid sequence

• missense - added an amino acid to the sequence

• nonsense - added a STOP codon to the sequence

• nonsense - added an amino acid to the sequence

Multiple Choice

Look at the two nucleotide sequences for a section of DNA given.

What type of mutation is shown in the copied sequence?

• Insertion

• Deletion

• substitution

• Nondisjunction