UNIT 4: Genetic Processes 1 & 2

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Genetic Processes

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Phases of Mitosis Interphase: everything is duplicated Prophase: - nuclear membrane starts to break down, nuclei goes to separate ends of the cell, chromosome group in the middle Metaphase: nuclear membrane gone, chromosomes line up in the middle of the cell, little fingers come from centromeres toward the chromosomes Anaphase: -fingers start pulling chromosome towards the centromeres, cell wall begins dipping in the middle to divide Telophase: -chromsomes start to unwind, membranes begin to form, cell walls begin to divide more
Cell in Anaphase Diagram
Importance of Mitosis - Mitosis enables cells to repair and reproduce asexually
Stages of the Cell Cycle Interphase: G1: cellular contents excluding the chromosomes are duplicated , S (DNA Synthesis): chromosomes are duplicated , G2: cell checks duplicated chromosomes for errors and does repairs Mitotic Phase: Mitosis, cytokenesis
Stages of Meiosis Meiosis 1 (homologous chromosomes separate): Prophase 1: duplicated chromosomes pairs with its corresponding homologous chromosome, they then exchange portions of DNA Metaphase 1: tetrads (pairs of homologous chromosomes) move to the middle of the cell and line up Anaphase 1: homologous chromosomes separate from the tetrad and migrate to opposite poles of the spindle. Sister chromatids remain attached Telophase 1: nuclear membrane re-forms around each cluster of chromosomes
Stages of Meiosis (cont.) Prophase 2: in each haploid daughter cell a spindle forms and attaches to the centromeres of the sister chromatids Metaphase 2: the spindle attached to the centromeres moves the sister chromatids so that they line up in the middle of the cell Anaphase 2: sister chromatids separate and move to opposite poles of the cell. Telophase 2: Chromosomes are at the poles. Separate nuclei begin to form around each group of chromosomes. Cytokinesis splits the cells one more time resulting in 4 haploid daughter cells
Importance of Meiosis - it ensures that all organisms produced via sexual reproduction contain the correct number of chromosomes - also produces genetic variation by way of the process of recombination.
What does "crossing over" refer to? - Chromosomal crossover (or crossing over) is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction
What are "homologous chromosomes"? One chromosome of each homologous pair comes from the mother (called a maternal chromosome) and one comes from the father (paternal chromsosome). Homologous chromosomes are similar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same.
What is "random assortment"? Pairs of similar chromosomes are called homologous chromosomes. During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.
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