notes

1. Mutations

2. Why are proteins so important?
• Proteins determine what a person’s traits
(physical features) will be.

3. 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.

4. 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.

5. Processing Piece:
• These are examples of insertions:
AAT  ACAT
TAC  TACA
• Try to come up with your own definition for an
insertion.

6. Processing Piece:
• These are examples of deletions:
AAT  AT
TAC  TC
• Try to come up with your own definition for an
deletion.

7. Processing Piece:
• These are examples of substitutions:
AAT  ACAT
TAC  TACA
• Try to come up with your own definition for an
substitution.

8. 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

9. Processing Piece:
• These are examples of point mutations:
AAT  ACAT
TAC  TACA
• These are NOT examples of point mutations:
AAT  AATAAT
AAT  T
Try to come up with a definition.

10. Processing Piece:
• These are examples of missense mutations:
Ser – leu –leu  Ser – tyr – leu
Met – ala - ser  Ala – ala - ser
• These are NOT examples of missense mutations:
Ser – leu –leu  Ala – tyr – leu
Met – ala - ser  Cyt – ana - ser
Try to come up with a definition.

11. Processing Piece:
• These are examples of nonsense mutations:
Ser – leu –leu  Ser – stop
Met – ala - ser  Ala – stop
Try to come up with a definition.

12. Processing Piece:
• These are examples of silent mutations:
Ser  Ser
Ala  Ala
Try to come up with a definition.

13. 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.

14. Processing Piece:
• This is an example of frameshift mutations:
AAT CAT TAT GAT  ATC ATT ATG AT
Try to come up with a definition.

15. 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.)

16. 4) Original DNA: ATA AGG GAA CGA.
• mRNA:
_____________________________________
_
• Amino acids:
_____________________________________
_

17. 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?

18. 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?

19. Exit Ticket
1) 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?