Hawler Medical University Molecular Basis of Mutation Bashdar M. Hussen MSc.Biotechnology Hawler Medical University bashdar@res.hmu.edu.iq bmhscience@yahoo.com
What Are Mutations? Changes in the nucleotide sequence of DNA May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring
What Causes Mutations? There are two ways Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage Mistakes when DNA is copied
Are Mutations Helpful or Harmful? Some type of skin cancers and leukemia result from somatic mutations Some mutations may improve an organism’s survival (beneficial)
Types of Gene Mutations Include: Point Mutations Base Substitutions (transitions and transversions) Base additions or deletions Frameshift Mutation
Frameshift Mutation Inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Proteins built incorrectly
Point mutations can also be categorized functionally Silent substitutions: the mutation changes one codon for A.A into another codon for that same A.A Missense mutations: the codon for one amino acid is replaced by a codon for another amino acid (code for a different amino acid). Nonsense mutations: the codon for one amino acid is replaced by a translation termination (stop) codon.
Point Mutation Sickle Cell disease is the result of one nucleotide substitution (GAG to GTG) Occurs in the hemoglobin gene
New mutations are categorized as induced and spontaneous Induced mutations are defined as those that arise after purposeful treatment with mutagens, environmental agents that are known to increase the rate of mutations. Spontaneous mutations are those that arise in the absence of known mutagen treatment
Spontaneous mutations and human diseases Muscular dystrophy (CTG repeats) Fragile mental retardation (CGG repeats ) Becker muscular dystrophy (BMD) Dystrophin is a rod-shaped cytoplasmic protein, and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix
Thank You 11/29/2018