Unit 1. The cell Types of chromosomes From DNA to chromosomes The cell cycle has 2 parts: reproduction (mitosis or meiosis) and interphase. During interphase the DNA will be unrolled, despiralized, so that the cells can produce proteins from that DNA. MITOSIS MEIOSIS MEIOSIS I MEIOSIS II The result of Meiosis is 4 different cells with the chromatids distributed from each chromosome distributed randomly, and having half of them undergone a process of recombination. In this way, the number of possible gene combinations after each meiosis is enormous. Prophase I The centrioles begin to migrate to the poles and release microtubules to form the spindle fibers. DNA is packaged into chromosomes. CSs are paired by homologues (those that have the same size, and the same types of genes) In this phase RECOMBINATION OR CROSSOVER occurs. CSs exchange pieces of chromatid. The nuclear membrane ruptures. Microtubules (the fibers of use) bind to the kinetochores of each chromosome. Metaphase I The homologous CS are placed in pairs on the equatorial plate Anaphase I The spindle fibers pull the complete CS towards the poles (thus complete CS have separated). Telophase I The spindle fibers disappear and centrioles are formed. CSs are unpacked The nuclear membrane is formed. DNA DURING MEIOSIS I
