1. HEREDITY & DEVELOPMENT WARNING: THIS IS GOING TO GET PRETTY SCIENCE-Y

2. INHERITED HUMAN TRAITS  Physical traits are observable characteristics determined by specific segments of DNA called genes. Genes are the basic units of heredity. They contain directions for many characteristics, such as eye color and shape, hair color, etc.  Multiple genes are grouped together to form chromosomes, which reside in the nucleus of the cell. Every cell (except eggs and sperm) in an individual’s body contains two copies of each gene.  Genes store the information needed for the cell to assemble proteins, which eventually yield specific physical traits.

3. Alleles & Inheritance  Most genes have two or more variations, called alleles. For example, the gene for hairline shape has two alleles - widow’s peak or straight. An individual may inherit two identical or two different alleles from their parents. When two different alleles are present they interact in specific ways.  The alleles interact in what is called a dominant or a recessive manner. The traits due to dominant alleles are always observed, even when a recessive allele is present. Traits due to recessive alleles are only observed when two recessive alleles are present.

4. Uncovering Genetic Influences  Family Method The closer the blood relationship you have with someone, the more genetic material you have in common.  First-degree relatives  - Parents/siblings –  50% shared genetic  material  Second-degree relatives  - Aunts/uncles/grandparents - 25% shared genetic material  Cousins - 12.5% shared genetic material  Twin studies  Two types of twins  - Monozygotic (MZ) Identical (share 100% of genes)  - Dizygotic (DZ) Fraternal (share 50% of genes)  Adoptees Method  Look at ways that children who are adopted very early in life are similar to their biological parents.  When children raised by adoptive parents are more like biological parents, there is evidence that genetic predisposition plays a role.

5. GENETIC DISORDERS  A genetic disorder is a disease that is caused by an abnormality in an individual's DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes.  Some people are born with too many, too few, chromosomes. - People with Down Syndrome usually have an extra 21st chromosome - A number of disorders (e.g., Turner’s Syndrome, Klinefelter’s Syndrome, XYY complement, XXX Syndrome) are caused by missing or extra sex of chromosomes.  Many disorders are triggered when a child inherits two recessive alleles. - Examples include cystic fibrosis, PKU, albinism, and Tay-sachs disease  Most inherited disorders are very rare.