Genetic Code & Mutations

Exons and Introns EXONS EXONS A segment of DNA in eukaryotic organisms that codes for a specific amino acid A segment of DNA in eukaryotic organisms that codes for a specific amino acid INTRONS INTRONS A segment of DNA that does NOT code for an amino acid. A segment of DNA that does NOT code for an amino acid.

Confusing genetic terms: Polypeptide = a chain of amino acids. Protein = a complex structure composed of polypeptides Amino acids = smallest structural unit of a polypeptide. Gene = a distinct unit of material found on a chromosome

“Language of RNA” RNA contains 4 different bases: A,U,C,G RNA contains 4 different bases: A,U,C,G The genetic code is responsible for building all the proteins in the body using 20 different amino acids. The genetic code is responsible for building all the proteins in the body using 20 different amino acids. Codon: three consecutive nucleotides that specify a single amino acid. Codon: three consecutive nucleotides that specify a single amino acid. Amino acids are attached to make a polypeptide, protein. Amino acids are attached to make a polypeptide, protein. Anticodon: the complimentary RNA bases of a codon. Anticodon: the complimentary RNA bases of a codon.

Codons A three letter “word” that specifies an amino acid.

There are “start” codons & “stop” codons There are “start” codons & “stop” codons Tells ribosome where to start reading the RNA strand. Tells ribosome where to start reading the RNA strand.

Genetic code:

Translation TRANSLATION: the process by which mRNA is read and protein produced. TRANSLATION: the process by which mRNA is read and protein produced. mRNA has a codon that codes for a particular anticodon, attached to tRNA (translational RNA) mRNA has a codon that codes for a particular anticodon, attached to tRNA (translational RNA) tRNA also has the amino acid attached to it. tRNA also has the amino acid attached to it.

tRNA (transfer) approx. 80 nucleotides in length. approx. 80 nucleotides in length. Cross-like shape Cross-like shape At one end there is an anticodon At one end there is an anticodon At other end an amino acid is attached At other end an amino acid is attached

Mutations Mutation is a change in genetic material. Mutation is a change in genetic material. Types of Mutations: Types of Mutations: Gene Mutations Gene Mutations A. Point Mutation B. Frameshift Mutation Chromosomal Mutations Chromosomal Mutations

Gene Mutations Point Mutation: occur at a single point Point Mutation: occur at a single point Includes substitution, addition, and deletions of bases. Includes substitution, addition, and deletions of bases. May only change one amino acid coded for. May only change one amino acid coded for. Frameshift Mutation: when codons get changed because of additions or deletions Frameshift Mutation: when codons get changed because of additions or deletions Changes the combinations so that different amino acids are coded for. Changes the combinations so that different amino acids are coded for.

Chromosomal Mutations These mutations change the entire chromosome. These mutations change the entire chromosome. Types include: Types include: Deletions: loses part of chromosome Deletions: loses part of chromosome Duplications: doubles part of chromosome Duplications: doubles part of chromosome Inversions: inverts part of chromosome Inversions: inverts part of chromosome Translocations: takes part of chromosome and moves it to other part of chromosome Translocations: takes part of chromosome and moves it to other part of chromosome

 Translocation Insertion 

A six-legged green frog A white American alligator shows a genetic mutation known as leucism. This allele controls migration of pigment cells during development; absence in cells leads to white patches on the skin An African clawed frog (Xenopus laevis), mutated, with three hind legs

Control of gene expression Genes are often like light switches that can be turned off and on. Operon = occur in prokaryotes. (bacteria) different genes that work together to activate gene functions

Eukaryotic gene expression Controlled by complex sequences of DNA. Controlled by complex sequences of DNA. Example: “TATA box” Example: “TATA box”

Hox and Oncogenes Hox genes Hox genes Genes that actively control embryonic development. Genes that actively control embryonic development. Oncogenes Oncogenes Genes known to cause cancer. Genes known to cause cancer. Usually these are switched “off”, but can be switched “on” by a number of factors. Usually these are switched “off”, but can be switched “on” by a number of factors.