BSC2011- UNIT 2Lecture 11: Reproduction(Sections: 13.1, 13.2)- Know that asexual reproduction results in genetically identical offspring- Know that asexual reproduction is genetically the same as cloning- Know that sexual reproduction results in genetically similar but not identical offspring- Know that asexual reproduction is the result of mitosis- Know that chromosomes exist as homologous pairs in diploids- Know and understand why meiosis produces haploid daughter cells from diploid parentso Meiosis is a type of cell division that reduces the number of setsof chromosomes from two to one in the gametes, counterbalancing the doubling that occurs at fertilization. End product is 4 haploid cells. Haploid cells: gametes contain a single set of chromosomes. For humans, the haploid number is 23. Diploid cells: any cell with two chromosome sets. For humans, the diploid number is 46 (2n = 46)- Know that sexual life cycles alternate meiosiso Plants and some species of algae exhibit a second type of life cycle called alternation of generations. This type includes both diploid and haploid stages that are Multicellular. The Multicellular diploid stage is called the sporophyte. Meiosis in the sporophyte produces haploid cells called spores. Unlike a gamete, a haploid spore doesn’t fuse with anothercell but divides mitotically, generating a Multicellular haploid stage called the gametophyte. - Know that sexual life cycles vary in the timing of meiosis and fertilizationHomologous Chromosome: (homologous pair) The two chromosomes composing a pair have the same length, centromere position, and staining pattern. One homologous chromosome is inherited from the organism’s father, the other from the mother.Sister Chromatid: Two copies of a duplicated chromosome attached to each other by proteins at centromere and, sometimes, along the arms. Whilejoined, two sister chromatids form a chromosome.- Sister chromatids from the of same chromosome are genetically identicalGamete: A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote. (Sperm and Eggs)Zygote: The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg. (Fertilized Egg)Meiosis: A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. - It results in cells with half the number of chromosome sets as theoriginal cell. Fertilization: The union of haploid gametes to produce a diploid zygote. Gonad: The male and female sex organs; the gamete-producing organs in most animals (testes and ovaries)Sexual Reproduction: A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes. Asexual Reproduction: The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). -In most cases, the offspring are genetically identical to the parentClone: A lineage of genetically identical individuals or cells. COMPARING… Mitosis- genetically identical daughter cells- Development, growth, and asexual reproduction- Produces haploid cellsMeiosis- Daughter cells contain a subset of Parent cell’s genes.- Sexual Reproduction (formation of gametes)Lecture 12: Meiosis(Sections: 13.3, 13.4)- Understand that meiosis produces haploid daughter cells by separating homologous pairs of chromosomes so that one homolog goes to each cell. - Know the stages of meiosis and what happens in eacho Interphase: Chromosomes duplicate into sister chromatids.o Prophase 1: Chromosomes begin to condense, and homologs loosely pair along their lengths, aligned gene by gene. o Metaphase 1: Pairs of homologous chromosomes are nowarranged at the metaphase plate, with one chromosome in each pair facing each pole. o Anaphase 1: Breakdown of proteins responsible for sister chromatid cohesion along chromatid arms allows homologsto separate. The homologs move toward opposite poles, guided by the spindle apparatus. o Telophase 1 and Cytokinesis: Each half of the cell has acomplete haploid set of duplicated chromosomes. Cytokinesis forms two haploid daughter cells. - Understand that the pairing of homologs and crossing over both occur in Prophase 1. - Understand that both the random assortment of homologs into daughter cells and the process of crossing over result in genetically variable gametes- Know that special molecules prevent the separation of sister chromatids in Anaphase 1- Know the stages of meiosis and what happens in eacho Interphase: Chromosomes duplicate into sister chromatids.o Prophase 1: Chromosomes begin to condense, and homologs loosely pair along their lengths, aligned gene by gene. o Metaphase 1: Pairs of homologous chromosomes are nowarranged at the metaphase plate, with one chromosome in each pair facing each pole. o Anaphase 1: Breakdown of proteins responsible for sister chromatid cohesion along chromatid arms allows homologsto separate. The homologs move toward opposite poles, guided by the spindle apparatus.o Telophase 1 and Cytokinesis: Each half of the cell has acomplete haploid set of duplicated chromosomes. Cytokinesis forms two haploid daughter cells. - Know the meiosis consists of two stages: meiosis 1 and 2o Meiosis 1: Homologous chromosomes are separated.o Meiosis 2: Sister chromatids are separatedSynapsis: During prophase 1, this state allows the pairing and physical connection of duplicated homologous chromosomes. Crossing Over: The reciprocal exchange of genetic material between non-sister chromatids, during prophase 1. Chiasma: The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase 1 between homologous non-sister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion. Meiosis I: the first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell. Meiosis II: The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell. Lecture 13: Mendelian Genetics(Section: 14.1)- How did Mendel do his experiments? o
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