Meiosis Prophase I 2 homologous chromosomes form a synapse by a protein now they look like bivalent tetrads cause they re 4 chromatids Parts of DNA are exchanged location of cross over is called chiasmata Formation of chiasmata and recombination crossover Metaphase I All chromosomes align Anaphase I Homologous chromosome separate with the exchanges they ve done in prophase I for genetic variation In phase II no DNA synthesis the chromosomes don t replicate themselves You just have 1 more division to make it into half Start with 1 and end with 4 haploid cells Your meiosis starts from birth Ch 14 We thought we had 100 000 genes and have 30 000 The human genome project Gregor Mendel True breeding purple plants will always produce purple plants Ch 15 Genes are the ones associated with chromosomes Morgan Hunt Homologous are there in mitosis and meiosis but they only pair up in meiosis You don t know sex of baby until 2months it has to do with the presence of SRY gene DAX1 used in sex reversal operations and sensitive dosage In sperms the cross over is not much because they lac homologous chromosomes Sex linked trait that particular gene that is defected is either carried on X or Y If it s X linked it s carried on X chromosome and Y linked is only on Y chromosome X chromosome more than 1000 genes Y chromosome 78 genes Epigenetics gene code is same just altering the way it s expressed Recombinant offspring combination from both parents When the genes are close together they come together as a package deal Even if the genes are on the same chromosome they can cross over and assort independently if they are far apart Higher than 50 recombination means either genes are far apart on the chromosome or just on different chromosomes Translocation can become a problem when the piece of segment goes to another chromosome the control system changes Non dysfunction when there s one extra trisomy one less is monopsony Genomic imprinting the phenotype of offspring is based on what allele the parent contributed
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