1. Chromosomes Autosomes – Chromosomes that do not determine the sex of an individual We have 44 autosomes or 22 pairs Sex chromosomes 2 sex chromosomes – XX female – XY male Karyotype – The picture of the chromosomes in their condensed form

2. Sex Determination Humans & many animals – X & Y the presence of the Y determines male – contains the region SRY (sex- determining region of Y) – XX or X or XXX all female – XY of XXY both male (Y by its self is not viable) – X-O system (grasshopper) XX vs X XX female, X male – Z-W System (chicken) ZW female, ZZ male – Haploid/diploid system (bees) diploid - female, haploid - male

3. Expression of Traits - Recessive Recessive disorders – homozygous individuals are called carriers – cystic fibrosis – sickle-cell – mating of close relatives increases the penetrance of recessive disorders

4. Expression of Traits - Dominant Dominant disorders – achondroplasia (dwarfism) – Huntington's Multifactorial (Nature + Nurture) – Polygenetic inheritance Many genes affect a single trait – diseases that have a genetic basis but there penetrance are tied to environmental issues heart disease diabetes (type II)

5. Expression of Traits - Codominant An intermediate expression or expression of both phenotypes – ABO Blood System

6. Expression of Traits – Sex Linked Sex linked – Expressed ALWAYS in the male (X d of X D ) – May have low penetrance (expression) due to random X inactivation unless homozygous (X D X d )

7. Pedigree Chart Pedigree charts help track the expression of traits through generations. – Recessive… only expressed if homozygous recessive (dd) – Dominant expressed…expressed always (DD or Dd or D_)