| A | B |
|---|
| meiosis | nuclear division that reduces the # of chomosomes by half |
| phases of meosis | 2 nuclear divisions- diploid cells divide-4 haploid cells |
| meiosis 1 (1) | 1st division- homologus chromosomes are separated into separate cells |
| meiosis 2 (1) | 2nd division- chromatids of each chromosome are separated into separate cells |
| result of meiosis 2 | all daughter cells have half the number of chromosomes as the parent cell |
| prophase 1 | DNA strands coil- become chromosomes- spindle fibers appear-nuclear membrane and nucleolus dissappear |
| synapsis | paring of homologus chromosomes |
| tetrad | means 4- 4 chromatids |
| in forming chromatids: | parts of chromatids may be exchanged |
| crossing over | exchange of genetic material between maternal and paternal chromosomes |
| genetic recombination | producing a new mixture of genetic material |
| metaphase 1 | tetrads move to the equator- homologus pairs of chromosomes remain together |
| anaphase 1 | each homologus chromosome moves to opposite poles |
| independant assortment | random separation of homologus chromosomes |
| telophase 1 | cytoplasm divides, forming two daughter cells |
| meiosis 1 (2) | parent cell produces 2 daughter cells- 1 member of each pair of homologus chromosomes |
| meiosis 2 (2) | occurs in each cell formed during meiosis 1- not preceded by DNA replication |
| prophase 2 | chromosomes of some organisms coil again- new spindle fibers form |
| metaphase 2 | chromosomes move cell together |
| anaphase 2 | each sister chromatid is moved toward an opposite pole |
| telophase 2 | spindle dissolves nuclear membrane forms around chromosomes in each of the 4 cells- cytokenesis occurs |
| 2 nuclear divisions | 4 daughter cells form a single parent cell- formation of sperm and egg |
| male | development-diploid divides- 4 haploid cells- spermatids |
| spermatogenesis | production of sperm cells |
| female | diploid cell divides- 1 mature egg cells-ovum- cytoplasm divides unequally and the egg cells receives the most |
| oogenesis | production of egg cells |
| asexual reproduction | offspring from one parent-without the union of gametes |
| unicellular organisms | binary fission or mitotic division |
| multicellular | offspring are genetically identical to their parents- budding |
| sexual reproduction | offspring through meiosis-fusion of gametes- offspring- genetically different from both parents |
| meiosis genes are combined through: | crossing over and independent assortment |
| evolutionary advantage | species adapt rapidly to new conditions |
