Transcript LN #23
Mutations Ms. Garcia California Content Standard Genetics 4c. Students know how mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in an encoded protein. Mutation: A Change in DNA Any change in DNA sequence (order) of nucleotides is called a mutation. Changing the DNA will result in the production of a changed protein. The changes may be beneficial or harmful. Point Mutation Normal Point Mutation Change in a single base pair in DNA. The change results in an incorrect amino acid being added to the protein chain during translation. The change of one amino acid affects the shape of the entire protein. Frameshift Mutations Normal Frameshift Mutation A single base is added or deleted from DNA and shifts the reading of codons by one base. Adding or deleting one base in DNA will change almost every amino acid after the mutation. Chromosomal Mutations Parts of a chromosome are broken off and lost during mitosis or meiosis. Chromosomes break and rejoin incorrectly Join backwards Chromosome part join with the wrong chromosome. Nondisjunction Nondisjunction = when chromosomes do not separate. Causes of Mutations Spontaneous Mutations Mutations that just happen • Ex. a mistake in base pairing during DNA replication. Mutations because of Environmental Factors. Mutagen = anything that can cause a change in DNA • ex. high energy radiation, chemicals and high temperature. Mutation can happen in reproductive and body cells. Reproductive Cells Genes in sperm or egg are changed. If mutated sperm or egg go through fertilization the mutation will be passed on to the offspring. Mutated gene can produce a harmful or beneficial trait in the offspring. Beneficial mutations are more rare. Body Cells A mutation in body cells is not passed on to the offspring. Damage done to a gene affects the cells ability to do its job. When a body cell undergoes mitosis, the new cells will also have the mutation. Summary What are mutations? What is a point mutation? What is a frameshift mutation? What are chromosomal mutations? What causes mutations? In what type of cell does a mutation need to occur in order for it to be passed to the next generation? Do Pre Read 11.3 on page 302.