Transcript Mutations
Mutations A mutation is any change in the DNA sequence. Mutations in Reproductive Cells • Only in gametes could be passed on to offspring Mutations in Body Cells • Somatic (normal/non-sex cells) • cannot be passed on to offspring Types of Mutations • Gene mutationschanges to a specific gene. (DNA base pairs) • Chromosomal mutations- changes to a portion of the chromosome • Can effect many genes Different Types of Gene Mutations • Point mutation-a change in a single base pair in the DNA. THE DOG BIT THE CAT THE DOG BIT THE CAR THE DOG BAT THE CAR THE DIG BAT THE CAR Point Mutation Frameshift Mutation • a single base pair is added or deleted, causing a shift in how the strand will be read. THE DOG BIT THE CAT THE DO BIT THE CAT THE DOB ITT HEC AT Chromosome Mutations • Deletion-part of a chromosome is left out. There is a small section of chromosome #5 that has been deleted • Insertion-part of a chromatid breaks off & attaches to its sister chromatid. • Inversion-part of a chromosome breaks off & reinserts backwards. • Translocation-part of one chromosome breaks off & is added to a different chromosome. • Nondisjunction- have an abnormal number of chromosomes – Caused by errors in Mitosis or Meiosis • Most die before birth • Results in either monosomy or trisomy Down’s Syndrome Traits • Down’s Syndrome is an example of nondisjunction • Results from trisomy of the 21st pair of chromsomes (3 chromosomes) • Mental retardation, short stature, heart defects, most are sterile, and other problems Down’s Syndrome There is an extra chromosome on the 21st pair Turner’s Syndrome Traits • Turner’s Syndrome occurs only in females • Results from monosomy X • People with syndrome are sterile • Secondary sex characteristics don’t develop What causes mutations? • spontaneous mistakes • environment – any agent that can cause a change in DNA is called a mutagen. (x-rays, UV light, asbestos) DNA Repair • enzymes in our cells remove the incorrect nucleotides & replace them with the right ones. – this works well, but is not perfect