Standard 3.2.1-Explain the role of meiosis in sexual reproduction and genetic variation
Fertilization and meiosis alternate in sexual life cycles
Meiosis reduces chromosome number from diploid to haploid
Meiosis reduces chromosome number from diploid to haploid
Interphase 1
Cells undergo a round of dna replication forming duplicate chromosomes.
Prophase 1
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Metaphase 1
Spindle fibers attach to the chromosomes.
Anaphase 1
The fibers pull the homologous chromosomes toward opposite ends of the cell.
Telophase 1 and cytokinesis
Nuclear membranes form. The cell separates into two cells
Meiosis 2 Prophase 2
Meiosis i results in two haploid {N} daughter cells each with half the number of chromosomes as the original cell
Metaphase 2
The chromosomes line up in a similar way to the metaphase stage of mitosis.
Anaphase 2
The sister chromatids separate and move toward opposite ends of the cells
Telophase 2 and cytokinesis
Meiosis 2 results in four haploid {N} daughter cells
Meiosis increases genetic varation by the gene combinations in the offspring due to sexual reproduction. Crossing over and independent assortement
Crossing over is between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes.
Non Disjunction- during meiosis. Nondisjunction means that a chromosome pair failed to separate during the meiotic division. This will create one daughter cell with an extra chromosome and another daughter cell with one too few chromosomes.