Download Perubahan bahan genetik: Mutasi

Perubahan bahan genetik: Mutasi
What is a Mutation?
A mutation : a permanent change in the DNA
sequence of a gene.
Mutations in a gene's DNA sequence can alter
the amino acid sequence of the protein encoded
by the gene.
How does this happen?
Like words in a sentence, the DNA sequence of
each gene determines the amino acid sequence for
the protein it encodes.
The DNA sequence is interpreted in groups of three
nucleotide bases, called codons.
Each codon specifies a single amino acid in a
protein.
Mutate a sentence!
 We can think about the DNA sequence of a gene as
a sentence made up entirely of three-letter words.
 In the sequence, each three-letter word is a codon,
specifying a single amino acid in a protein.
 Have a look at this sentence:
Thesunwashotbuttheoldmandidnotgethishat
 If you were to split this sentence into individual
three-letter words, you would probably read it like
this:
The sun was hot but the old man did not get his hat.
The sun was hot but the old man did not get his hat.
This sentence represents a gene.
Each letter corresponds to a nucleotide
base, and each word represents a codon.
What if you shifted the three-letter "reading
frame?"
You would end up with
• T hes unw ash otb utt heo ldm and idn otg eth ish at.
• Or
Th esu nwa sho tbu tth eol dma ndi dno tge thi sha t.
 As you can see, only one of these three "reading
frames" translates into an understandable sentence.
 In the same way, only one three-letter reading frame
within a gene codes for the correct protein.
 Now, going back to the original sentence:
Thesunwashotbuttheoldmandidnotgethishat
 See how you can mutate the reading frame of this
sentence by inserting or deleting letters within the
sentence.
 It's easy to make mutations that create "nonsense"
sentences.
Mutasi
•
•
•
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Genotype
Phenotype
Mutasi
Point mutation
Isolation of mutant
Notasi
 Pheontype :
Phe- : tidak mampu mensintesis phenylaanine
Lac+: mampu menggunakan laktosa sebagai
sumber karbon
Genotype:
pheA :gen yang mengkode sintesis Phe
lacZ : gen yang mengkode kemampuan
menggunakan laktosa
Mutasi
• Mutation: any change in the nucleotide
sequence of the DNA in cell
 change the phenotype
silent (non essential, non-coding part of
genome)
• Point mutation: the change in the DNA
sequence range of a single base
Point mutation
1. Samesense mutation: same amino acid
inserted
2. Mis-sense mutation: different amino acid
inserted
3. Non-sense mutation: the creation of a
termination codon- protein synthesis stops.
4. Frame shift mutation: from a point that a
nucleotide is inserted or deleted the amino
acids are altered.
1.Same sense mutation
5’AUG CCU UCA AGA UGU GGG CAA-3’
Met Pro Ser Arg Cys Gly Gln

5’AUG CCU UCA AGA UGU GGA CAA-3’
Met Pro Ser Arg Cys Gly Gln
2.Mis-sense mutatio
5’AUG CCU UCA AGA UGU GGG CAA-3’
Met Pro Ser Arg Cys Gly Gln

5’AUG CCU UCA GGA UGU GGG CAA-3’
Met Pro Ser Gly Cys Gly Gln
3. Non-sense mutation: the creation of a
termination codon- protein synthesis stops.
5’AUG CCU UCA AGA UGU GGG CAA-3’
Met Pro Ser Arg Cys Gly Gln

5’AUG CCU UCA AGA UGA GGG CAA-3’
Met Pro Ser Arg Stop
Frame shift mutation:
5’AUG CCU UCA AGA UGU GGG CAA-3’
Met Pro Ser Arg Cys Gly Gln
 deletion
5’AUG CCU UCA AG UGU GGG CAA-3’
Met Pro Ser Arg Cys Gly Gln

5’AUG CCU UCA AGU GUG GGC AA-3’
Met Pro Ser
Ser
Val
Gly
etc.