1. Human Heredity 14.1 and 14.2

2. Human Chromosomes The 46 human chromosomes can be arranged as a karyotype (picture of chromosomes arranged in homologous pairs): Female Male

3. Human Chromosomes Two of the 46 are sex chromosomes (female = XX, male = XY) ALL egg cells carry a single X; sperm carry either an X or a Y Women can only contribute X’s, while men contribute half X and half Y The other 44 are autosomes

4. Human Pedigrees Some human traits are inherited like traits in Mendel’s garden peas, with simple dominance and recessivity We can construct a pedigree to trace the inheritance of traits through a family.

5. Constructing Human Pedigrees Rule One: Use a square for males and a circle for females. Rule Two: Use a horizontal line to link parents Rule Three: Use a vertical line to link parents to children Rule Four: Color in all members with the trait

6. Constructing Human Pedigrees Let’s trace a white lock of hair above the forehead through a family: 1. Draw two parents; the male has the trait 2. They have three children; one male that has the trait, one female who doesn’t, and one female who does 3. The male has two girls with a female with the trait; only one child gets the trait

7. Constructing Human Pedigrees 4. The female without the trait has no partner or children 5. The female with the trait has a partner with the trait; they have two boys and a girl. One boy and the girl have the trait. IS THIS TRAIT DOMINANT OR RECESSIVE? - Predict the genotypes, starting at the top…

8. Sex Linked Traits (14.2) Some alleles for non-gender traits are found on the X Chromosome Men are more likely to have disorders from these alleles because they have one X All alleles on the man’s X chromosome will physically show up! Women can just be carriers of a disorder if one X is normal

9. Sex-Linked Trait Problem X C = normal vision X c = color blind Mom is carrier of color-blindness allele, but is not color blind (X C X c ) Dad has normal vision X C Normal daughter X C Y Normal son X C X c Carrier Daughter X c Y Color blind son XCXC XcXc XCXC Y

10. Sex Linked Traits Hemophilia and Muscular Dystrophy are also common sex-linked traits Hemophilia: lack protein for normal blood clotting Muscular Dystrophy: progressive weakening and loss of muscle