Inheritance Patterns and Human Genetics
Mutation
A change in DNA is called a mutation. Mutations can involve
entire chromosomes or specific genes. They may take place in any cell.
Germ cell mutations occur in sex cells, such as eggs and sperm. They do
not affect the organism itself but are passed on to offspring. Somatic
mutations take place in body cells.Deletion occurs when a piece of a chromosome
breaks off. All of the information on that piece is lost. Inversion occurs
when a piece breaks from a chromosome and reattaches itself to the chromosome
in the reverse orientation. IF a broken piece attaches to a non-homologous
chromosome, the results is a translocation. Another kind of chromosomal
mutation, called nondisjunction, occurs when a replicated chromosome pair
fails to separate during cell division. The substitution, addition, or
removal of a single nitrogen base is called a point mutation. The addition
or deletion of a nitrogen base is a point mutation called a frame-shift
mutation. Often, however, mutations are caused by mutagens - environmental
factors that damage DNA. Researches often use a procedure called the Ames
test to identify mutagenic substances.
