MUTATIONS

Definition = A change in the DNA sequence of an organism that could: MUTATIONS Definition = A change in the DNA sequence of an organism that could: have no effect on the organism alter the product of a gene Prevent a gene from functioning properly

1. Type of Mutations a. Germinal Mutation A mutation in the DNA of a germ cell that will be transmitted to the offspring by way of the resulting gamete (egg or sperm) * a heritable mutation

b. Somatic-cell Mutation A mutation in a body cell that is not heritable.

2. Causes of Mutations DNA fails to copy accurately = random, common

2. Mutagen =environmental factor that alters the DNA. Radiation (X rays, gamma rays) UV light Chemicals (bromine, benzene, preservatives, pesticides, tobacco smoke, produced when meats are cooked at high temp.) Viruses and bacteria Radioactive elements Particulates (Asbestos, coal dust) Metals = Arsenic, cadmium, nickel

3. Chromosome Mutations A change in the structure of a chromosome A change in the number of chromosomes.

Types of Chromosome Mutations a.Deletion = Missing regions of a chromosome resulting in the lack of 1 or more genes. Examples = Angelman’s Syndrome and Prader–Willi syndrome both result from the loss of a section of chromosome #15.

Angelman Syndrome VS Prader-Willi Syndrome

Chromosome Mutations b. Inversion = A chromosome segment is removed, turned upside down and reinserted back into the chromosome.

Chromosome Mutations c. Translocation = a fragment of a chromosome is removed and attaches onto a non-homologous chromosome .

Chromosome Mutations d. Nondisjuction = the failure of homologous chromosomes or sister chromatids to separate during anaphase I or II of meiosis; leads to individuals with too or too few chromosomes. Examples: Klinefelter’s Syndrome Patau Syndrome Trisomy X Turner’s Syndrome Edward’s Syndrome

Nondisjunction:

Nondisjunction

4. Gene Mutations A change in the nucleotide sequence that makes up a gene.

a. Point Mutation - Change, removal, or addition of a single nucleotide (base = letter) in a gene sequence

Types of Point Mutations: 1. Substitution = exchange of a single nucleotide for another:

Point Mutation = Gene Substitution

Types of Point Mutations: 2. Deletion = removal of one or more nucleotides

Types of Point Mutations: 3. Insertion = addition of one or more nucleotides to the gene sequence.

Gene Mutation WS – complete now

Gene Mutation WS PQ – write your answers on the piece of scrap paper provided Which types of mutations from the worksheet caused a change(s) in the resulting amino acid sequence of the lactase enzyme? Which type of mutation caused no change in the resulting amino acid sequence of the lactase enzyme? 3. What type of mutation occurred in your answer to #2 above? A. gene point mutation-substitution B. gene point mutation-deletion C. gene point mutation-insertion Some mutations cause a change in the way the mRNA is read by altering the codons and eliminating a “stop” codon at the end. For this reason, these types of mutations are also called _?_ mutations. 4. Which mutation from the worksheet caused a slight change (only 1 A.A. is different) in the resulting amino acid sequence of the lactase enzyme? (+1)

Frame shift : Caused by deletions and/or insertions that causes a change in the grouping of the codons = a change in the reading frame during translation.

Some mutations are: Silent = change still codes for the same amino acid Missense = codes for a different amino acid in the sequence Nonsense = codes for a “stop” codon before the protein is fully produced.