Gene Expression Mutation polymorphism 1 How are genes

Gene – Expression – Mutation - polymorphism 1

How are genes expressed ? DNA Transcription Cap Poly(A) Pre-m. RNA Splicing Lariat intron Cap Poly(A) m. RNA Degradation Nucleus m. RNA transport Translation Cytoplasm Ribosome PROTEIN 2

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 3

The cause of mutations 1. Spontaneous error in replication that evade proofreading function of the DNA polymerases that synthesize new polynucleotides mismatches 4

1. Error in replication 5

2. Effect of mutagen 6

Mutation : In-frame mutation maintain reading frame (codon is intact) Out of frame/frameshift mutation disrupt reading frame 1. Point mutation 2. Deletion 3. Insertion 4. Duplication 7

Point mutation common (single site mutation) : replace one nucleotide with another Divided into two catagories: 1. Transitions : are purine-to purine or pyrimidine-topyrimidine changes : A G, G A, C T, or T C. 2. Transversions : are purine-to-pyrimidine or pyrimidine-to-purine changes: A C, A T, G C, G T, C A, C G, T A or T G 8

Point mutation: Single nucleotide change - deletion - insertion - missense - nonsense (create a stop codon) - silent (no amino acid alteration) 9

Point mutation : Missense Silent Missense 10

Polymorphism: Different nucleotide sequence that occurs in the population as a whole Deletion Insertion Patient (+) Control (-) Mutation Patient (+) Control (+) Polymorphism Duplication Missense Silent Most polymorphism occurs in intronic sequence 11