Biology Unit Two notes for Exam 2 Chapters 14 1 14 4 15 1 15 5 Lecture 10 Chapters 13 1 13 2 Asexual reproduction results in genetically identical offspring Asexual reproduction is the genetic equivalent of cloning Sexual reproduction results in genetically similar but not identical offspring Asexual reproduction is the result of mitosis Chromosomes exist as homologous pairs in diploids 2N Meiosis produces haploid cells from diploid cells Sexual life cycles alternate meiosis and fertilization Sexual life cycles vary in the timing of meiosis and fertilization Terms Haploid cell containing only one set of chromosomes Diploid a cell containing two sets of chromosomes one set inherited from each parent Homolgous chromosome homologous pair a pair of chromosomes the same length centromere position and staining pattern that posses genes for the same characters at corresponding loci One homologous chromosome is inherited from the organism s father one from the mother sister chromatid either of two copies of a duplicated chromosome attached to each other by proteins at the centromere and sometimes along the arms While joined two sister chromatids make up one chromosome chromatids are eventually separated during mitosis or meiosis II gamete a haploid reproductive cell such as an egg or a sperm Gametes unite during sexual reproduction to produce a diploid cell zygote the diploid production of haploid gametes during fertilization a fertilized egg meiosis modified type of cell division in sexually reproducing organisms consisting of two round of cell division but one round of DNA replication it results in half the number of chromosomes sets fertilization the union of haploid gametes to produce a diploid zygote gonad the male or female sex organs the gamete producing organs in most animals sexual reproduction a type of reproduction which two parents give rise to off spring that have unique combinations of genes inherited from the gametes of the parents asexual reproduction the generation of offspring from a single parent that occurs without the fusion of gametes in most cases the offspring are genetically identical to the parent clone 1 lineage of genetically individuals or cells 2 in proper usage a single individual organism that genetically identical to another individual 3 to make one or more genetic replicas of an individual or cell spore in the life cycle of a plant or alga undergoing alternation of generations a haploid cell produced in the sporophyte by meosis A spore can divide by mitosis to develop into a multicellular haploid individual the gametophyte without fusing with another cell 2 in fungi a haploid cell produced either sexually or asexually that produces a mycelium after germination gametophyte in organisms that have alternation of generations the multicellular haploid form that produces haploid gametes by mitosis The haploid gametes unite and develop into sporophytes sporophyte in organisms that have alternation of generations the multicellular diploid form that results from the union of gametes The sporophyte produces haploid spores by meiosis that develop into gametophytes Each chromosome in our body has one homolog from our mom and one from our dad which means that our chromosomes are genetically similar but not identical A gamete is haploid During fertilization a gamete becomes a zygote and is diploid Lecture 11 Chapters 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 that meiosis consists of two stages meiosis I and meiosis II Know that the end product of meiosis is 4 haploid cells Know that homologous chromosomes are separated in meiosis I Know that sister chromatids are separated in meiosis II Know the names of the stages of meiosis and what happens in each Understand that the pairing of homologs and crossing over both occur in prophase I Understand that both the random assortment of homologs into daughter cells and the process of crossing over result in genetically variable gametes Know the differences between mitosis and meiosis Know that special molecules prevent the separation of sister chromatids in anaphase I Terms Synapsis process during prophase I replicated homologs pair up and become physically connected along their lengths by a zipper like protein structure the synaptonemal complex crossing over genetic rearrangement between nonsister chromatids chiasma X shaped region that remain intact during late prophase it s a physical manifestation of crossing over meiosis I separates homologous chromosomes 1 prophase 1 replicated homologous chromosomes pair and exchange segments 2 metaphase 1 chromosomes line up by homologous pairs 3 anaphase 1 each pair of homologous chromosomes separate 4 telophase and cytokinesis 1 two haploid cells form each containing two sister chromatids meiosis II separates sisters chromatids 1 Prophase II 2 Metaphase II 3 Anaphase II sister chromosomes separate 4 Telophase II and cytokinesis haploid daughter cells forming segregation two alleles for a heritable character segregate during gamete formation and end up in different gametes Meiosis 1 produces haploid daughter cells from diploid parents members of each pair are separated homologous chromosomes pieces of chromosomes are exchanged Prophase 1 members of homologous pair pair up and are physically attached Anaphase 1 they are separated but sister chromatids are still together Meiosis II each cell splits sister chromatids in two Homologous chromosomes same genes may or may not have different alleles for these chormosomes Alternation of Generations Reproduction Sporophyte multicellular diploid stage Spore haploid produced by sporophyte meiosis divide mitotically to create multicellular haploid stage Gameophyte multicellular haploid stage Gamete by mitosis of gameophyte gametes are formed Fertilization Occurs by fusion of gametes with then develops in sporophyte Ratios Mendel s experiment mixing 1 trait Mendel s experiment mixing 2 traits 3 1 9 3 3 1 Lecture 13 ch 14 1 How did Mendel do his experiments How do Mendel s results relate to blending Inheritance Law of Segregation Law of Independent Assortment Terms Gene a discrete unit of hereditary information consisting of specific nucleotide sequence in DNA Allele any of the alternative versions of a gene that produce distinguishable phenotypic effects Locus a specific place along the length of a chromosome where a given gene is
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