BIOLOGY FALL 2014 MUTATIONS

WHAT ARE MUTATIONS? Mutations = changes in the genetic material Mutations can happen when cells make mistakes in copying their own DNA or can be caused by radiation or chemicals in the environment.

WHAT ARE MUTAGENS? Mutagens = agents in the environment that can change DNA Examples: UV Rays in Sunshine Industrial Chemicals X-rays

KINDS OF MUTATIONS Mutations that produce changes in whole chromosomes = chromosomal mutations Mutations that produce changes in a single gene = gene mutations

GENE MUTATIONS Three categories: 1.Substitutions 2.Deletions 3.Insertions

SUBSTITUTIONS Substitutions = changes one base to another A T T C G A G C T A T T C T A G C T How many amino acids are changed?

SUBSTITUTION EXAMPLE: SICKLE CELL ANEMIA Cause: (autosomal recessive) an A is changed to a T  glutamate to valine Results in the formation of abnormal hemoglobin that distorts certain blood cells Heterozyous – Malaria Resistance

DELETION Deletions = a piece of DNA code is lost A T T C G A G C T A T T C A G C T How many amino acids are changed?

DELETION EXAMPLE: CYSTIC FIBROSIS Different kinds of cystic fibrosis, but most commonly is caused by deletions Life expectancy ~ 37 years old

INSERTIONS Insertion : Extra piece of DNA is added A T T C G A G C T A T T C G C A G C T How many amino acids are changed?

INSERTION EXAMPLE: ALS ALS is a neurodegenerative disorder leading to dementia and muscle weakness Most common mutation that causes ALS is many insertions of “GGGGCC” which overproduces incorrect proteins that damage brain cells

GENE MUTATIONS Substitutions usually affect no more than a single amino acid, but deletions and insertions can have a more dramatic effect.

GENE MUTATIONS Deletions and insertions can cause frame shift mutations which means that multiple bases in the code are changed. thefatcatatetherat thefatcataatetherat

FRAME SHIFT MUTATIONS Frame shift mutations change every amino acid in the protein that follows the shift. Frame shifts can alter a protein so much that it is unable to function!

The location of the frame shift is important!! At the beginning: the fat cat ate the rat The fac ata tet her at At the end: the fat cat ate the rat the fat cat ate thr at Mutations at the BEGINNING of the gene damage MORE of the code!!