T U E S D AY I N B I O L O GY
 BUILD-A-BUG ACTIVIT Y
 Build your bug and turn in to your box
 Mutations Notes
 Mutations practice
QUIZ NEXT CLASS: Transcription and Translation
REMINDERS THAT YOU NEED TO KNOW!!!
 Transcription: transcribing DNA into mRNA
 Example
 DNA: T A C A A AT T A G C G
 mRNA: AUG-UUU-AAU-CGC
DNA  RNA
A
T
G
C
U
A
C
G
 Translation: translating the message in RNA into an
amino acid sequence
( us e yo ur c o do n c h a r t )
 Example
 mRNA: A U G - U U U - A A U - C G C
 AA:
Meth-Phen-Asp-Arg
 Gene expression: What traits does your bug have? Build a
bug to express the genes!!
MUTATIONS
What are DNA Mutations?
• Mutation – a random
change in the sequence of
a gene
• Caused by:
– Mistakes in DNA replication
process
– Environmental agents that
damage DNA
ATCGA
TAGCT
ATCGA
TAGCT
ATCAA
TAGCT
Types of DNA Mutations
•
•
•
•
•
Point mutation/Substitution
Inversion
Insertion
Deletion
Translocation
C T C G A T A
Types of DNA Mutations
• Point mutation/Substitution – one base replaced with
another base
• Inversion – order of two or more bases is reversed
Types of DNA Mutations
• Insertion – addition of one or more new bases
• Deletion – removal of one or more bases
Types of DNA Mutations
• Translocation – movement of one or more bases to a
new location in a different DNA sequence
DNA Mutations
• Changes in sequence of a gene can cause changes to the
protein that is produced during translation
• Can affect proteins produced in different ways:
–
–
–
–
Silent mutations
Missense mutations
Nonsense mutations
Frameshift mutations
Silent Mutations
Silent mutation – mutation that causes no change in
amino acid sequence
• Genetic code has redundancies
• Caused by point mutations
…TACAACCTCACC…
…ATGTTGGAGTGG…
…AUGUUGGAGUGG…
DNA
(transcription)
RNA
…TACAATCTCACC…
…ATGTTAGAGTGG…
…AUGUUAGAGUGG…
(translation)
Met-Leu-Glu-Trp…
Protein
Met-Leu-Glu-Trp…
Missense Mutations
Missense mutation – mutation that changes the identity of
an amino acid added
• Most often because of point mutations
• May be because of inversions
…TACAACCTAACC…
…ATGTTGGATTGG…
…AUGUUGGAUUGG…
DNA
(transcription)
RNA
…TACAACCTCACC…
…ATGTTGGAGTGG…
…AUGUUGGAGUGG…
(translation)
Met-Leu-Asp-Trp…
Protein
Met-Leu-Glu-Trp…
Nonsense Mutations
Nonsense mutations – mutation that shortens a protein by
replacing an amino acid codon with a stop codon
• Most often because of point mutations
• Large impact on protein produced
…TACAACATGACC…
…ATGTTGTACTGG…
…AUGUUGUACUGG…
DNA
(transcription)
RNA
…TACAACATCACC…
…ATGTTGTAGTGG…
…AUGUUGUAGUGG…
(translation)
Met-Phen-Tyr-Trp…
Protein
Met-Phen-STOP
Frameshift Mutations
Frameshift mutation – mutation that alters the reading
frame in which codons are translated
• Caused by insertions, deletions, and translocations
• Large impact on protein produced
…TACAACATGACCCTA…
…ATGTTGTACTGGGAT…
…AUGUUGUAUUGGGAU…
DNA
(transcription)
RNA
…TACAACTATGACCCTA…
…ATGTTGATACTGGGAT…
…AUGUUGAUAUUGGGAU…
(translation)
Met-Leu-Tyr-Trp-Asp…
Protein
Met-Leu-Ile-Leu-Gly…
DNA Mutations and Survival
Mutations can be organized by their effect
• Neutral mutations – no effect on organism’s survival
– Increase genetic diversity in a species
– Example: human eye color
• Harmful mutations – decrease organism’s survival
– Produce genetic disorders or unfavorable traits
– Example: cancers
• Beneficial mutations – increase organism’s survival
– Produce favorable traits
– Example: antibiotic resistance in bacteria