| A | B |
|---|
| Kinetochores | A structure of proteins on each centromere where spindle fibers attach during prometaphase |
| Meiotic interphase | Only occurs before prophase I and and occurs more simultaneously than it does in mitosis (not divided into S, G1, and G2). First checkpoint is here |
| Metaphase I/II | Metaphase I: very much like mitosis but done with 4 chromosomes (in tetrads). Both sister chromosomes in each homolog are attached by kinetochore microtubules. Metaphase II: chromosomes positioned on metaphase plate, sister chromatids are pulled apart this time |
| Parthogenesis | A form of asexual reproduction in which females produce offspring from unfertilized eggs by using fusing the polar bodies in their gametes to form an offspring of the homogametic sex. Meiosis, no syngamy, then chromosome duplication |
| Polyploidy | A chromosomal alteration in which the organism has more than two complete chromosome sets, the result of an accident of cell division. Autopollyploids coppied their own genomes. Allopollyploids are polyploid due to genes from another species (often happens to plants) |
| Prophase I | 1. Chromatin begins to condense 2. Synapsis occurs: pairing and physical connection of duplicated homologous chromosomes; connected by protein structure called synaptonemal complex 3. Crossing over made possible by synaptonemal complex; maternal/paternal homologs randomly trade sections 5. Form tetrads with chiasma (crossing points) as the result of step three, proteins hold analogs together until ana I 5. The rest is like mitosis: spindle app forms, get rid of nuclear envelope, kinetochores used |
| Prophase II | Spindle app reforms (made mostly of microtubules, it moves to align sister chromatids during meiosis/mitosis and consists of centrosomes, asters, and microtubules) |
| Telophase I/II | Teolphase I: occurrs simultaneously with cytokinesis; nuclear envelope reforms and cell splits into 2 gamete precursor cells. Telo II: simultaneous with cytokinesis also, nuclear envelope reforms and splits into 4 haploid gametes |
| Anaphase I/II | A checkpoint occurs after each. Anaphase I: hgomologous replicated chromosomes move towards opposite ends of poles - each pole gets EITHER maternal or paternal chromosomes, which is CROSSING OVER. Anaphase II: centrosomes fully degenerate and sister chromatids separate and move towards poles |
| Aneuploidy | Having a different number of chromosomes than expected for chromosomes, monosomic = having only one; trisomic = having three. Causes: DNA doubling in the S phase of mitosis/meiosis and nondysjunction (occurs in anaphase in mitosis; in meiosis when homologs or sis chromatids stay together in ana I or ana II) |
| Autosomal chromosomes | All non-sex chromosomes (everything but X and Y). There are 22 pairs of autosomal chromosomes |
| Gamete precursor cell (germ cell) | Germ cells are diploid 2N but form haploid gametes (sperm/egg) after meiosis |
