MOLECULAR GENETICS Mutations Definition A change in the nucleotide sequence of a chromosome. * Usually in a single gene.

MUTATION Causes 1)Mutagens Definition Physical or chemical agents causing mutations.   2)Errors in Replication Mismatched pairs of nucleotides.    3)Transposons DNA sequences that move within and between chromosomes altering gene expression.

TRANSPOSON

TRANSPOSON

CHROMOSOMAL MUTATIONS Definition A genetic change that affects large regions of chromosomes or entire chromosomes.   Types Down Syndrome Extra chromosome 21 Fragile X Chromosome Breaking of an X chromosome near its tip.

DOWNS SYNDROME

FRAGILE X SYNDROME

GENE MUTATIONS Definition Types A change in the base sequence of DNA that alters individual genes. Types Point Mutation Substitution of one nucleotide Example AAA TCG -----> ACA TCG

GENE MUTATIONS Nonsense Mutation Definition Point mutation creating a stop codon.  

Tangier Disease

GENE MUTATION Missense Mutation Definition Point mutation coding for a different amino acid.

HUTCHINSON-GILFORD PROGERIA SYNDROME

GENE MUTATIONS Silent Mutation Definition Point mutation with no amino acid change.  

GENE MUTATIONS Frameshift Mutation Definition Point mutation causing a shift of nucleotides creating a different reading frame.      

CODON INSERTION CDON INSERTION

MOLECULAR GENETICS Gene Therapy Definition Providing a normal or functional gene to human cells to replace a nonfunctional gene.  

GENE THERAPY Nonhereditable Definition Treating the symptoms in the affected individual only.    

GENE THERAPY Hereditable Definition Preventing the disease from being passed on to the next generation.  

Good Gene Mutated Gene