Transcript Mutations - Everett School District

Genetic Mutations
Muytatogns?
Insertion
• A mutation in which extra base pairs are
inserted into a new place in the DNA.
CTGGAG
CTGGTGGAAG
Deletion
• A mutation in which a section of DNA (or
at least one base) is lost.
CTGGAG
CTAG
Possible Results of Insertions or Deletions?
“Frameshifts”
• Since DNA  mRNA and mRNA is read in
codons (triplets), insertions and deletions can
create amino acid sequences that are
meaningless.
• Consider the message:
The fat cat ate the hat
hef atc ata tet heh at
Substitution
• A mutation that exchanges one base for another.
CTGGAG
CTGGGG
• Possible Results:
– Change in codon  change in amino acid.
– Change in codon  no change in amino acid. “silent mutation”
– Change in codon to become a stop codon. “nonsense
mutation”
Chromosomal Alterations
• Can also lead to changes in DNA sequence  new traits
• Breakage of a chromosome may lead to four types of
changes
The boy cut his lip and ate the hot dog
Your tasks:
1.
2.
3.
3.
Copy the sequence and place a large box around it
Using the original sequence, insert two bases anywhere.
Write the resulting message as it would be read.
Using the original sequence, delete one base anywhere.
Write the resulting message as it would be read.
Using the original sequence, substitute one base to another.
Write the resulting message as it would be read.
Challenge: Write a DNA sequence and create a
substitution that would result in a silent mutation.