1. PEDIGREES (12.3) * a chart that shows how a trait and the genes that control it are inherited within a family. Symbols: female male mate/ marriage offspring

2. USES helpful in determining carriers (an individual who carries a recessive trait that is not expressed). to determine whether a trait is dominant or recessive. to determine whether a trait is heterozygous or homozygous dominant to determine whether a trait is sex-linked

3. Examples of recessive traits Tay-Sachs disease http://www.ninds.nih.gov/disorders/taysachs/taysachs.htm http://www.ninds.nih.gov/disorders/taysachs/taysachs.htm Cystic fibrosis http://www.nhlbi.nih.gov/health/dci/Diseases/cf/cf_what.html http://www.nhlbi.nih.gov/health/dci/Diseases/cf/cf_what.html Albinism *The allele is preserved in the population because the carriers are NOT affected.

4. Examples of dominant traits Freckles Widow’s peak Polydactyly Huntington’s disease http://www.ninds.nih.gov/disorders/huntington/huntington.htm http://www.ninds.nih.gov/disorders/huntington/huntington.htm *In many cases, a person who has inherited a dominant allele that produces a fatal disorder is likely to result in an early death…why is this important?