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Gene – Expression – Mutation - polymorphism. How are genes expressed ?. DNA . Transcription . Pre-mRNA. Cap. Poly(A ) . Splicing . Lariat intron. mRNA. Cap. Poly(A) . Degradation . Nucleus . mRNA transport . Translation . Cytoplasm. Ribosome. PROTEIN . MUTATION.
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How are genes expressed ? DNA Transcription Pre-mRNA Cap Poly(A) Splicing Lariat intron mRNA Cap Poly(A) Degradation Nucleus mRNA transport Translation Cytoplasm Ribosome PROTEIN
MUTATION Mutation is a change in the nucleotide sequence of genome, caused by a replication error or by a mutagen. Mutagen a chemical or physical agent that can cause a mutation in a DNA molecule
The cause of mutations • Spontaneouserror in replication that evade proofreading function of the DNA polymerases that synthesize new polynucleotides • mismatches
Mutation : In-frame mutation maintain reading frame (codon is intact) Out of frame/frameshift mutation disrupt reading frame • Point mutation • Deletion • Insertion • Duplication
Point mutation common (single site mutation) : replace one nucleotide with another • Divided into two catagories: • Transitions : are purine-to purine or pyrimidine-to-pyrimidine changes : AG, GA, CT, or TC. • Transversions : are purine-to-pyrimidine or pyrimidine-to-purine changes: AC, AT, GC, GT, CA, CG, TA or TG
Point mutation: Single nucleotide change - deletion - insertion - missense - nonsense (create a stop codon) - silent (no amino acid alteration)
Point mutation : Missense Missense Silent
Polymorphism: Different nucleotide sequence that occurs in the population as a whole Deletion Insertion Duplication Missense Silent Patient (+) Control (-) Patient (+) Control (+) Mutation Polymorphism Most polymorphism occurs in intronic sequence