Download Chapter 5 Heredity & Genetics

IV. Source of Gene Variations: When cells divide
each DNA molecule in the cell makes exact
copies of itself. But sometimes the cell makes a
mistake; bases may pair up incorrectly. The
codon are changed the altered gene is passed
on to the new cell.
A- Mutation is any permanent change in
the DNA of a cell.
1. Mutation increases with the exposure of
DNA to some chemicals ands radiation that
damage the DNA molecule.
B. Chromosome Mutation: When a piece of
chromosome breaks and are rearranged or
lost. During meiosis chromosomes mutation
may occur when chromosomes do not separate
evenly.
1. Muscular Dystrophy= Weak muscles.
2. Down Syndrome or Trisomy 21= is caused as a
result of a sex cell having too many 21st
chromosomes. The fertilized egg, contains three
21st chromosomes instead of two.
3. Importance of Mutations= are a source of new
traits or new forms of traits.