RNA and Mutations!

–RNA = ribonucleic acid (3 types) mRNA – messenger RNA takes information for protein to be made from DNA to the ribosome tRNA – transfer RNA carries amino acids to ribosomes, lines them up in the correct order according to mRNA rRNA – ribosomal RNA makes up the structure of the ribosome RNA

–RNA nucleotides are composed of phosphate ribose (sugar) and a base (adenine, guanine, cytosine and uracil) RNA

Mutations Random change in DNA sequence or genetic materialRandom change in DNA sequence or genetic material Caused by errors inCaused by errors in –Replication –Transcription –Cell division –External agents ChemicalsChemicals RadiationRadiation VirusesViruses Mutagens

Mutations may be: Helpful – longer beaks in a birdHelpful – longer beaks in a bird Harmful – causes a disease like cancerHarmful – causes a disease like cancer No effect – no change in proteinNo effect – no change in protein

Inheriting Mutations Two Types of CellsTwo Types of Cells –Body (somatic) Cells –Sex (germ) Cells –Mutations must be in sex cells to be passed on to offspring Skin cancer cannot be passed on from a parent’s skin cell to a child’s cells.Skin cancer cannot be passed on from a parent’s skin cell to a child’s cells.

GENE MUTATIONS Point Mutations –Occur at a single point in the DNA sequence Ex:DNA  TAC GCA TGG AAT RNA  AUG CGU ACC UUA AA  MET-ARG-THR-LEU

–But how does this affect the proteins being made? A substitution occurs and C is substituted with T DNA  TAC GTA TGG AAT RNA  AUG CAU ACC UUA AA  MET – HIS- THR-LEU

GENE MUTATIONS Frameshift Mutations –Occurs when a nucleotide is deleted or inserted in a DNA strand Bases are still read in groups of 3, so…it shifts the reading of all of the codons from that nucleotide on. –Ex:DNA  TAC GCA TGG AAT RNA  AUG CGU ACC UUA AA  MET- ARG- THR-LEU –But how does this affect the proteins being made? DNA  TAT CGC ATG GAA T RNA  AUA GCG UAC CUU A AA  ILE – ALA- TYR-LEU A human example of a frameshift mutation is Tay Sachs disease.

Genes or groups of genes can become incorrectly placed on a chromosome and cause a mutation Types: Insertion Deletion Inversion Translocation Inversion

Non-disjunction – when sister chromatids fail to separate correctly during meiosis Ex: Trisomy 21

Genes can be turned “off” or “on” –Activated or deactivated Activated – means the gene is expressed or the protein is made Deactivated means the gene is not expressed or no protein is made Exons and introns – –Much of the mRNA that is transcribed in the nucleus does not actually get translated –Some mRNA gets clipped out, enzymes do this called processing, maturing, or editing The part taken out = introns (interferring) The part that actually codes for the needed protein and goes to the ribosome to be translated is called the exon (that which is expressed)