Bellringer 10.29.12 Three consecutive bases in mRNA are known as what? Three consecutive bases in tRNA are known as what? How many codons are there? How many amino acids? Get your last sheet of notes from the cart! Cut it in half and share with a neighbor!

Mutations in DNA

Mutations What is a mutation? What is a mutagen? Any change in a DNA sequence What is a mutagen? External things that can change DNA What 4 things can cause a mutation? Mistakes in DNA replication radiation chemicals high temperatures

Types of Mutations Point Mutations or Substitutions: bases are mismatched GAG CTC CUC Leucine Correct DNA Correct mRNA Correct AA GCG CTC CGC Arginine A should pair with T, but instead G is mismatched to T Point mutation mutated mRNA Wrong AA

Mutations Example: Sickle Cell Anemia http://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_06

Mutations Frame-shift Mutation: when bases are added or removed, all of the codons that follow the mutation will be altered. Example THE DOG SAW THE CAT or THD OGS AWT HEC AT

Insertion: one or more new bases are inserted into a gene. Correct DNA: ATA CCG TGA TAT GGC ACT Correct mRNA: UAU GGC ACU Correct amino acids: Tyrosine Glycine Threonine Extra inserted base shifts how we read the codons (3 bases), which changes the amino acids Frameshift mutation ATG ACC GTG A in DNA: TAC TGG CAC T Mutated mRNA: UAC UGG CAC U Wrong amino acids: Tyrosine Tryptophan Histadine

Deletion- One or more bases are deleted.

Rate of Mutations in Human Gametes In humans, mutation rates range from about 1 in 100,000 - 1,000,000 gametes. A mutation in a gamete is inherited by the offspring

Results of Mutations Missense : ANY mutation that changes the codon and makes a different amino acid in the protein Nonsense : ANY mutation that changes a codon into one of the STOP codons Silent : ANY mutation that causes no change in the protein and cannot be detected without sequencing the gene

Repairs Proofreading enzymes are able to repair some damages to DNA

Only 1-2% of people in the world have red hair!!! Effects of Mutations Harmful—can cause diseases Helpful—can provide protection or a new trait (bacteria can mutate against our antibiotics, helpful for them) Neutral—nothing happens because the same protein is still made Only 1-2% of people in the world have red hair!!!

Mutations to control genes can transform one body part into another Mutations to control genes can transform one body part into another. Scientists have studied flies carrying Hox mutations that sprout legs on their foreheads instead of antennae!

Mutations in Humans

Name Mutations http://www.nature.ca/genome/04/0413_e.cfm Sickle Cell Anemia http://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_06 Name Mutations http://www.nature.ca/genome/04/0413_e.cfm

On a separate sheet of paper… Copy on of the following sequences: ATC GAT GTC ACC AAT ATG ATG CGA CTA TGG GAC CCC TGA GTT TTA CCG GGA AGA Change the sequence to mRNA Change the sequence to tRNA Perform a frame-shift mutation (insertion or deletion) to the original sequence Change the new sequence to mRNA Change the new sequence to tRNA