Chapter 11- Genetics Meiosis Principles of genetics require: -each organism inherits a single copy of every gene from each parent -during gamete formation, two sets of genes must separate, so each gamete contains just one set of genes

Chapter 11- Genetics Chromosome Number Fruit fly example: 8 chromosomes total 4 came from male parent 4 came from female parent Two sets are homologous

Chapter 11- Genetics Homologous chromosomes- paired chromosomes having genes for the same trait located at the same place on the chromosome Diploid- having two of each kind of chromosome (2n); normal body cells Diploid cells have two complete sets of chromosomes/two complete set of genes

Gametes of sexually reproducing organisms have only a single set of chromosomes Haploid- having one of each kind of chromosome (n) Fruit fly gametes would be n = 4

Chapter 11- Genetics Phases of Meiosis How haploid cells (gametes) produced from diploid cells (somatic cells) Meiosis- cell division that results in a gamete containing half the number (n) of chromosomes of its parent (2n) Involves two rounds of division: -Meiosis I -Meiosis II

Phases of Meiosisof Meiosis I Similar to mitosis Four phases the same: prophase I, metaphase I, anaphase I, and telophase I

Chapter 11- Genetics Differences- Prophase I: Pairing of homologous chromosomes to form tetrad (4 chromatids) Crossing over- exchange of genetic material between non-sister chromatids of homologous chromosomes Shuffles genes like a deck of cards

Meiosis II Second round of division (reduction) NO chromosome replication Phases just like meiosis I: Prophase II, metaphase II, anaphase II, telophase II At end of division cycle, each cell contains haploid # of chromosomes (n)

Chapter 11- Genetics Gamete Formation In male animals, gametes produced through meiosis called sperm In some plants, pollen contains sperm cells In female animals, only one cell produced is made into a gamete Cytokinesis is uneven: produces one egg and 3 polar bodies

Chapter 11- Genetics Comparing Mitosis & Meiosis Sexual reproductionAsexual reproduction Formation of gametesMulticellular organisms: growth & repair 4 genetically different haploid cells 2 identical diploid cells MeiosisMitosis