Mutations

Why are proteins so important?

• Proteins determine what a person’s traits (physical features) will be.

Why do people have different traits?• People have different traits (like different eye color

and hair color) because they have different nucleotide sequences.

• Different nucleotide sequences result in different types of proteins, which results in different physical traits.

What is a mutation?• When the DNA changes.• Changes in the nucleotide sequence can

change the amino acids, which changes the protein that is made, which changes a person’s physical traits.

Processing Piece:

• These are examples of insertions:AAT ACATTAC TACA

• Try to come up with your own definition for an insertion.

Processing Piece:

• These are examples of deletions:AAT ATTAC TC

• Try to come up with your own definition for an deletion.

Processing Piece:

• These are examples of substitutions:AAT ACATTAC TACA

• Try to come up with your own definition for an substitution.

What are insertions, deletions, and substitutions?

• Insertion: Extra bases (“letters”) are added to the nucleotide sequence.

Example: AAT AATC• Deletion: Bases are removed from the nucleotide

sequence.Example: AAT AT• Substitution: A base is replaced with another.Example: AAT ACT

Processing Piece:

• These are examples of point mutations:AAT ACATTAC TACA

• These are NOT examples of point mutations:AAT AATAAT

AAT TTry to come up with a definition.

Processing Piece:

• These are examples of missense mutations:Ser – leu –leu Ser – tyr – leuMet – ala - ser Ala – ala - ser

• These are NOT examples of missense mutations:Ser – leu –leu Ala – tyr – leu

Met – ala - ser Cyt – ana - serTry to come up with a definition.

Processing Piece:

• These are examples of nonsense mutations:Ser – leu –leu Ser – stopMet – ala - ser Ala – stop

Try to come up with a definition.

Processing Piece:

• These are examples of silent mutations:Ser Ser Ala Ala

Try to come up with a definition.

What are point, missense, nonsense, and silent mutations?

• Point mutation: when a single base (“letter”) is inserted, deleted, or substituted.

• Missense mutation: When there is a substitution, and 1 amino acid changes.

• Nonsense mutation: When a mutation creates a stop codon in the gene, and the polypeptide chain is cut short.

• Silent mutation: When there is a substitution, but none of the amino acids change.

Processing Piece:

• This is an example of frameshift mutations:AAT CAT TAT GAT ATC ATT ATG AT

Try to come up with a definition.

What is a frameshift mutation?

• When 1 or 2 bases are inserted or deleted, and every codon after the mutation changes.

(Example: TAG TAG TAG becomes AGT AGT AG after the first A is deleted.)

4) Original DNA: ATA AGG GAA CGA. • mRNA:

______________________________________• Amino acids:

______________________________________

Original DNA: ATA AGG GAA CGA. 5) Now remove the T from the orginal DNA (from #4), and write the new DNA sequence below: • Mutated DNA:

_________________________________________________• Mutated mRNA:

_________________________________________________• Mutated amino acids:

_________________________________________________ • Was the mutation an insertion, deletion, or substitution?

_______________________________________________• Did the mutation cause a frameshift? _________ How do you

know?

6) Now remove the C from the original DNA. Is this an insertion, deletion, or substitution? __________• Mutated DNA:

________________________________________• Mutated mRNA:

_________________________________________• Mutated amino acids:

________________________________________• Did this mutation cause a frameshift? _________

How do you know?

Exit Ticket1) Are different physical traits caused by different

amounts of DNA, or by different nucleotide sequences?

2) Which will cause more changes to the amino acid sequence: Inserting one base in the middle of a gene, or inserting 3 bases at the beginning of a gene?

3) Why?