GENETIC MUTATIONS

Sexual Reproduction Results in variations Variations help organisms adapt Allow breeders to develop new strains of plants/animals Most variations come from segregation and crossing over in meiosis

Source of Variations Most variations come from: Segregation Crossing over

Mutations Mutations are sudden changes in the structure or amount of genetic material Most mutations are harmful; some are beneficial (i.e. ones that allow species to meet needs of environment) Ehlers-Danlos syndrome is a group of disorders that affect connective tissues, which are tissues that support the skin, bones, blood vessels, and other organs. Defects in connective tissues cause the signs and symptoms of Ehlers-Danlos syndrome, which vary from mildly loose joints to life-threatening complications.

Types of Mutations 2 Main Types: Chromosome Mutation = changes structure of all/part of chromosome Gene Mutation = affects a gene on a chromosome Mutation must be in DNA of sex cells in order for it to be passed on. Mutations in body cells can’t be passed on.

What Causes Mutations Random error in DNA replication Environmental Factors (called mutagens) Radiation (X-rays) UV light Chemicals (chloroform and mustard gas)

Chromosome Mutations Translocation One part of a chromosome is transferred to a non-homologous chromosome

Chromosome Mutations 2) Inversion One part of a chromosome is rotated (reverses order of genes)

Chromosome Mutations 3) Addition One part of a chromosome breaks off and attaches to a homologous chromosome

Chromosome Mutations 4) Deletion One part of a chromosome breaks off. This results in a loss of some genes E.g. Angleman’s Syndrome (Chromsome #15) Angelman syndrome (AS) is a neurological disorder first described in 1965 by an English physician named Dr. Harry Angelman.  Symptoms are usually evident after the age of three, and are characterized by severe congenital mental retardation, unusual facial appearance, and muscular abnormalities. Who gets it? Symptoms of Angelman syndrome include a stiff, unstable jerky gait, absent or diminished speech skills, hand flapping, excessive laughter/unusually happy demeanor, developmental delay, and small head size (microcephaly).  Some patients may also develop epilepsy and have problems with balance.

Chromosome Mutations 5) Non-disjunction Addition or loss of a whole chromosome (ones that usually separate during meiosis remain together)

Chromosome Mutations 6) Polyploidy More than normal copy of chromosomes

Gene Mutations Genes tell the cell what order to arrange amino acids (to form proteins) Changes in the DNA sequence will change the message transcribed into mRNA & likely change the protein Types of Mutations: Point Mutation Base Substitution

Point Mutation Single nucleotide in a gene is changed This is drastic as all triple codons beyond are changed This makes the gene useless and the organism will lack the protein normally made by the gene

Base Substitution One base in a nucleotide is substituted for another. This changes 1 codon and one amino acid Results in a protein that doesn’t function normally E.g. PKU Substitution of GT to AT