BIO 207 Exam 4 Practice Questions and Complete Solutions

When DNA is not repaired or cannot be repaired, what is the end result? Apoptosis- programmed cell death or mutation. A mutation occurs in a dog egg that changes a A to a T. This egg is fertilized and a puppy is born. What are the effects, if any? If the mutation is recessive, there will be no change in phenotype. If the mutation is dominant, there will be a change in phenotype. If the mutation is silent, there will be no change in phenotype. The puppy now has a 50% chance of transmitting the mutation to future offspring. (Answer: All of the choices are potential effects). A nonsense mutation is A mutation that results in early termination of the polypeptide. Proofreading repairs Repairs errors made in DNA replication by DNA Poll III are repaired by DNA Poll III. Human DNA polymerases also have this repair capability. Mismatch repair Certain repair proteins including endo- and exo- nucleases are stimulated to excise the incorrect nt. DNA Pol fills in gaps. Ligase seals the nicks. Errors in humans in this pathways are found in certain hereditary cancers, like hereditary nonpolyposis colon cancer. Nucleotide Excision Repair The pathway repairs bulky lesions in DNA that distort the double helix. Mutations in this pathways in humans cause Xertoderma pigmentosum. Double strand break repair This pathway repairs breaks made to both strands of DNA i a double helix. Mutations in this pathway in humans lead to familial predisposition to breast and ovarian cancer, to X-ray hypersensitivity, Fanconi anermia etc.. Mutations can cause damage in Behavior, phenotype, biochemical pathways, gene regulation (Answer: All of the above). A silent mutation is A mutation that results in no change on amino acid. A missense mutation is Mutation that results in substitution of one amino acid for another. Suppose I have a frame shift mutant in a yeast strain generated by deletion of 1bp. I treat the yeast with a mutagen and analyze one of the descendant colonies that has reverted (gone back to) wild type phenotype. Which of the following is the most likely to have caused the revision. There has been an insertion of 1bp, or a deletion of two bp, probably near the original deletion mutation. Spontaneous Mutation Arise spontaneously (no known cause; often errors in replication)