Genetic code
Codons and their functions
A codon is made of 3 base pairs. There are 64 codons total. Among them, 1 codon (AUG) encodes methionine and starts the translation of all proteins. 61 codons encode 20 amino acids, and 3 codons are stop codons, marking the end of protein translation. This is known as the redundant code.
Mutations and their impact
Nonsense mutations
mRNA Normal: GGC CAU GAG UUG CAU UGA AU
Protein: Met Leu Gln Ala Lys Phe Gly
mRNA Nonsense: A GGCU G UGU UGC AU A UUG C AA
Protein: Met Leu Ala Gln Lys Phe Gly
Silent mutations
mRNA Normal: GGCA G UU G AU G UGC AA C AU A
Protein: Met Leu Ala Gln Lys Phe Gly
Sequence Variant mRNA: GGU A GUU GCC AUG AUU GAA AU
Protein: Met Leu Gln Ala Lys Phe Gly
Missense mutations
mRNA Normal: GGCA G UU GCC AUG AUU GAA AU
Protein: Met Leu Gln Ala Lys Phe Gly
mRNA Missense: AGC G UU GCC AUG AUU GAA AU
Protein: Met Leu Gln Ala Lys Phe Ser
Frameshift mutations
mRNA Normal: GGCA G UU GCC AUG AUU GAA AU
Protein: Met Leu Gln Ala Lys Phe Gly
mRNA Frameshift: GCA G UU G GA AU UGC ACA AU G
Protein: Met Lys Leu Ala
Examples of mutations
- Normal: THE BIG RED DOG RAN OUT.
- Missense: THE BIG RAD DOG RAN OUT.
- Nonsense: THE BIG RED.
- Frameshift (deletion): THE BRE DDO GRA.
- Frameshift (insertion): THE BIG RED ZDO GRA.
Point mutations
A point mutation is a change in a single base pair.
RNA processing
Exon Intron Exon Intron Exon
DNA Transcription
Primary mRNA: AGGU
Processing Mature mRNA Translation Protein
Splice-Site Mutations
Exon 1 Intron Exon 2 Intron Exon 3
Exon 2 Exon 3 Exon 1 Altered mRNA
Other types of mutations
- Mutations in regulatory regions of the gene
- Large deletions or insertions
- Chromosomal translocations or inversions
- Types of Mutations
- Point Mutations
- Silent
- Missense
- Nonsense
- Frameshift
- Deletion/Insertion
- Rearrangement
- Gain
- Loss
- New
Polymorphism
Cambiamento della sequenza del DNA che non altera le funzioni della proteina (definizione comune, non corretta tecnicamente).
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Recensioni
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