Determining the Basis of Life Chapter 6 Lesson 4

Lesson Introduction What is meiosis? How is it different than mitosis? How is meiosis important to genetic variation? What things occur during meiosis to guarantee genetic variation?

Meiosis Cell division used in the sexual reproduction of organisms One parent cell produces 4 daughter cells Parent cell = original cell Daughter cells = newly produced cells Each daughter cell will have half the number of chromosomes as the parent cell

Meiosis Parent cell has 2 chromosomes for each loci Loci = numbered location of chromosomes in an organism Example: Humans have 23 loci Each cell has 46 chromosomes 23 came from mother 23 came from father

Meiosis Terminology Homologous Chromosomes Diploid cell 2 chromosomes at the same loci (1 from each parent) Diploid cell Cells containing homologous chromosomes for each loci Normal body cells

Meiosis Terminology Haploid cell Zygote Cells with 1 chromosomes for each loci (reproductive cells) Zygote Diploid cell that forms after 2 haploid reproductive cells fuse (join)

Meiosis Stages Completes the same stages as mitosis, but does so 2 times. Stages Meiosis I Interphase Prophase I Metaphase I Anaphase I (eggs stop) Telophase I Cytokinesis I Meiosis II Prophase II Metaphase II Anaphase II Telophase II Cytokinesis II

Meiosis I Metaphase I Interphase Prophase I Cytokinesis I Telophase I Anaphase I

Meiosis II Metaphase II Prophase II 4 daughter cells, all 1N Cytokinesis II Telophase II Anaphase II

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