1. Chromosomal Basis of Inheritance Tracing Heredity through Inheritance of Specific Chromosomes

2. Sex Determination Sex Chromosomes : homologous chromosomes that differ in size and genetic composition between males and females Sex Chromosomes : homologous chromosomes that differ in size and genetic composition between males and females HumanChromosomeXY Size and gene number Larger 2142 genes Smaller 326 genes GeneticComposition Multiple genes unrelated to gender Single gene influences gender: TDF = testis determining factor

3. Sex Determination Autosome: any chromosome that is not a sex chromosome Autosome: any chromosome that is not a sex chromosome Humans have 22 pairs of autosomes and 1 pair of sex chromosomes Humans have 22 pairs of autosomes and 1 pair of sex chromosomes

4. Human Karyotype showing homologous chromosome pairs

5. Sex Determination Female Male XX x XY XX x XY Phenotypic Ratio of Offspring

6. X-linked Genes Hemophilic Male Non-hemophilic Female Female (father is hemophilic) (father is hemophilic) Phenotypic Ratio of Offspring

7. Terms Specific to Sex-linked Genes Females Homogametic: only X found in gametes Can be homozygous or heterozygous for traits on X- chromosome Males Heterogametic: either X or Y in gametes Hemizygous for traits on the X-chromosome

8. Patterns of Inheritance Autosomal DominantAutosomal Dominant Autosomal RecessiveAutosomal Recessive X-linked DominantX-linked Dominant X-linked RecessiveX-linked Recessive Y-Linked InheritanceY-Linked Inheritance

9. Pedigree for Huntington’s Disease, an Autosomal Dominant Trait

10. Pedigree for Albinism, an Autosomal Recessive Trait

12. Pedigree for Colorblindness, an X-linked Recessive Trait