Genetics: the study of heredity Lesson 19 Genetics: the study of heredity

I. Genetics Heredity: Passing of traits from one generation to the next DNA: our genetic makeup

II. Meiosis Background Phase which sex cells form and genetic information is passed into them Homologs: chromosome pairs; contain genes for the same traits Chromatids: chromosomes attached together by centromere Chromosomes duplicate during interphase in cell cycle before meiosis

III. Meiosis I (4 phases) Prophase I: chromosomes shorten and thicken Metaphase I: Chromosomes line up in the center of the cell Anaphase I: Homologous pairs separate; chromatid pairs stay connected at centromere Telophase I: cytoplasm pinches together forming 2 daughter cells with homologous pairs in each new cell

IV. Meiosis II (begins immediately) Prophase II: chromatids move toward center MetaphaseII: chromatids align in middle of cell Anaphase II: Chromatids separate at centromere and move to opposite poles Telophase II: two new daughter cells form  4 haploid cells

V. Terms to know Alleles: different forms of a gene Genotype: genetic make-up for a trait Homozygous: (pure) both genes in a pair are identical (ex: RR, rr) Heterozygous: (hybrid) genes in a pair are different (ex: Rr) Phenotype: way a trait is expressed

VI. Incomplete dominance blended inheritance Both genes expressed to a certain degree Ex: Snapdragons Homozygous Dominant RR (red) crossed with Homozygous Recessive (white) rr Yields: Rr  pink color expressed

VII. Punnett Square Reginald C. Punnett Made to display results of genetic crosses Cross: random pairing of one gene from each pair from each parent

19.2 reflection questions (pg 182 YB) – write answers only Would each of your sex cells pass identical genes to an offspring? Does the offspring express a trait that neither parent did? How is this possible? How does meiosis result in four sex cells, each with one chromosome from each pair?