Genetics: Inheritance

Meiosis: Summary Diploid Cells (2n): two sets of chromosomes = “homologous chromosomes” One set from each parent normal body cells Produced by mitosis Haploid Cells (n): one set of chromosomes Gametes or sex cells Produced by meiosis Meiosis: 2 rounds of cell division that produce cells with HALF the number of chromosomes

Mitosis vs. Meiosis

Some Definitions…. Genetics: The scientific study of heredity. Trait: A specific characteristic of an individual. Gene: Sequence of DNA that codes for a protein (trait) Passed down from parent to offspring Allele: Different possible forms of a gene (one from each parent) Homozygous: 2 of the same allele for the same gene Heterozygous: different alleles for the same gene

Principle of Dominance Definition: Some alleles are dominant and others are recessive Which is the dominant allele for eye color, and which is the recessive? Which are the dominant alleles and which are the recessive? How do you know?

Genotype vs. Phenotype Genotype: the genetic makeup (i.e. combination of alleles for each particular gene) Phenotype: the physical traits exhibited by an organism (observable)

Complete Dominance – Dominant allele is shown in heterozygous Incomplete Dominance – blend between dominant and recessive Co-Dominance – Two different alleles are represented

Meiosis: How do we get genetic diversity? Crossing Over Random Orientation Fertilization

Recessive Genetic Disorders What common trends might genetic disorders have? (Think about what DNA and genes CODE for!) Examples: Cystic Fibrosis, Tay Sachs Disease, Albinism If a genetic disorder is RECESSIVE, what does that mean? How might completely healthy parents have a child with a recessive genetic disorder?