Chapter 15 Textbook Genetics

1. Mutations can be spontaneous or induced, somatic or germ-line, autosomal or sex-linked. Mutations can have many different effects on gene function depending on the type of nucleotide changes involved and the location of those mutations.

2. Spontaneous mutations occur in many ways, ranging from errors during DNA replication to damage caused to DNA bases as a result of normal cellular metabolism.

3. Mutations can be induced by many types of chemicals and radiation. These agents can damage both bases and the sugar-phosphate backbone of DNA molecules.

4. Single-gene mutations in humans cause a wide range of diseases. These mutations may be base-pair changes, insertions, deletions, and expanded DNA repeats.

5. Organisms counteract mutations using DNA repair systems including proofreading, mismatch repair, postreplication repair, photoreactivation repair, SOS repair, base excision repair, nucleotide excision repair, and double-strand break repair.

6. The Ames test allows scientists to estimate the mutagenicity and cancer-causing potential of chemical agents.

7. Transposable elements (TEs) can move within a genome, creating mutations and altering gene expression. In addition, TEs may contribute to evolution.

Insights and Solutions

1. A rare dominant mutation expressed at birth was studied in humans. Records showed that six cases were discovered in 40,000 live births. Family histories revealed that in two cases, the mutation was already present in one of the parents. Calculate the spontaneous mutation