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| 11592872712 | meiosis | Cell division that produces reproductive cells in sexually reproducing organisms - the number of chromosomes and genetic content will be reduced in half (reduction division process) - in mammals, meiosis occurs in the gonads (ovaries or testes) in response to estrogen or testosterone 2n -> n |  | 0 |
| 11592872713 | fertilization | the joining of a sperm cell and an egg cell n+n= 2n - random event with many possible outcomes |  | 1 |
| 11592872714 | autosomes | Any chromosome that is not a sex chromosome - human gamete has 22 of these | 2 | |
| 11592872715 | sex chromosome | one of two chromosomes that determines an individual's sex | 3 | |
| 11592872716 | X chromosome | the sex chromosome that is present in both sexes: singly in males and doubly in females | 4 | |
| 11592872717 | Y chromosome | sex chromosome found only in males | 5 | |
| 11592872718 | Sperm | haploid male sex cells produced by meiosis - determines the sex of the zygote | 6 | |
| 11592872719 | Meiosis 1 | - preceded by replication of homologous chromosomes 2n -> n + n | 7 | |
| 11592872720 | What does each daughter cell have? | half the # of chromosomes and half the # of the genetic content of the diploid parent cell | 8 | |
| 11592872721 | Meiosis is responsible for | genetic variations that exists in sexually reproducing species, between the parents and offspring, and even between two offspring from the same parents | 9 | |
| 11592872722 | Homologous Chromosomes | chromosomes having the same or allelic genes with genetic loci (positions) usually arranged in the same order - one chromosome inherited from the father, paternal and one from the mother, maternal - each gene in the pair of chromosomes codes for the same trait, but each chromosome may code for a different version of that trait, so homologous chromosomes are NOT identical to each other |  | 10 |
| 11592872723 | Alleles | different versions of a gene | 11 | |
| 11592872724 | Homologue | each of two chromosomes with identical structures | 12 | |
| 11592872725 | Prophase 1 | - nuclear envelope breaks down - spindle apparatus begins to develop - replicated maternal and paternal homologous chromosome form maternal and paternal sister chromatids - synapsis occurs - crossing over takes place | 13 | |
| 11592872726 | Synapsis | the union of the sister chromatids to form a tetrad of homologous chromosomes |  | 14 |
| 11592872727 | tetrad | the combination of maternal and paternal sister chromatids |  | 15 |
| 11592872728 | crossing over | - two non-sister chromatids in the tetrad cross over each other and exchange segments of DNA - this exchange produces recombinant chromatids - this event is the major source of genetic variations in gametes - chiasma ~~~~~~~~~~~~~~~~ - helps to preserve genetic variability within a species by allowing for virtually limitless combinations of genes in the transmission from parent to offspring - is estimated to occur approximately fifty-five times in male meiosis, and about seventy-five times in female meiosis | 16 | |
| 11592872729 | recombinant chromatids | two chromatids with new combinations of genes and inherited traits | 17 | |
| 11592872730 | chiasma | the X-shaped region where the exchange of genetic material occurs | 18 | |
| 11592872731 | Metaphase 1 | - tetrads line up at the metaphase plate - maternal and paternal sister chromatids in the tetrad are facing opposite poles (orientation to opposite poles is random) - kinetochores of all sister chromatids are attached to the spindle microtubules | 19 | |
| 11592872732 | Anaphase 1 | - the tetrads separate and sister chromatids move to opposite poles | 20 | |
| 11592872733 | independent assortment | the separation of the maternal and paternal sister chromatids randomly to opposite poles - maternal and paternal sister chromatids of the tetrad orient toward opposite poles randomly during metaphase 1 - the number of possible combinations due to independent assortment is 2^n , where n is the haploid number of species - for humans n=23 , so there are 2^23 possible combinations of chromosomes each time a cell undergoes meiosis - 2^23 = 8.4 million possible combinations | 21 | |
| 11592872734 | Telophase 1 | - a nuclear membrane encloses each set of homologous chromosomes - each nuclei now has a haploid (n) set of chromosomes due to independent assortment and there is a loss of genetic content in each cell - the genetic content has been reduced in half (n) because only some of the maternal and paternal chromosomes exist in each nucleus | 22 | |
| 11592872735 | Cytokinesis 1 | - division of the cytoplasm forms two haploid daughter cells | 23 | |
| 11592872736 | Meiosis 2 | - both daughter cells from Meiosis 1 now undergo Meiosis 2 - no chromosome replication occurs n -> n | 24 | |
| 11592872737 | Prophase 2 | - sister chromatids move toward the metaphase plate | 25 | |
| 11592872738 | Metaphase 2 | - sister chromatids are at the metaphase plate - two sister chromatids are no longer genetically identical to each other because of CROSSING OVER - kinetochores of sister chromatids attach to the microtubules | 26 | |
| 11592872739 | Anaphase 2 | - the sister chromatids separate (just like in mitosis) and move as two individual chromosomes toward opposite poles | 27 | |
| 11592872740 | Telophase 2 | - the chromosomes arrive at opposite poles - nuclei form around each set and the chromosomes unwind | 28 | |
| 11592872741 | Cytokinesis 2 | - division of the cytoplasm that results in four haploid daughter cells (the amount of DNA is reduced in half) and are genetically different from each other | 29 | |
| 11592872742 | Animal Male Gametogenesis | spermatogenesis | 30 | |
| 11592872743 | Spermatogenesis | - occurs in the testes due to testosterone - one diploid germ cell, spermatogonium, will produce 4 viable haploid sperm | 31 | |
| 11592872744 | Animal Female Gametogenesis | öogenesis - in humans, one or two months before a girl is born her öogonia (diploid germ cells) undergo replication, become primary öocytes and begin Meiosis 1 - primary öocytes "press the pause button" on their development in prophase 1 - the primary öocytes stay at this stage of development for over a decade until the onset of puberty and menstrual cycle - for the next 45 years or so, on a monthly basis, one primary oocyte resumes meiosis and completes meiosis 1 and meiosis 2 | 32 | |
| 11592872745 | Öogenesis | - occurs in the ovary due to estrogen - the polar bodies are smaller than the ovum due to unequal division of the cytoplasm and cannot be fertilized by sperm - the egg gets most of the cytoplasm to ensure that the egg has a larger store of food to nourish the developing embryo after fertilization - plant polar bodies are fertilized by a sperm cell - the fertilized polar bodies will develop and give rise to the endosperm - the fertilized ovum will become the plant embryo (2n) | 33 | |
| 11592872746 | primary öocyte | produces one haploid egg (ovum) and three haploid polar bodies | 34 | |
| 11592872747 | endosperm | surrounds the embryo and provides nutrition during development | 35 | |
| 11592872748 | the three mechanisms that are responsible for most of the variation that arise in each generation are | - independent assortment - crossing over - random fertilization | 36 | |
| 11592872749 | random fertilization | - to determine the probability that any one sperm will fertilized any particular egg, you multiply the probability of the separate independent assortment events together 2^23 x 2^23 = (2^n)^2 - the fusions of two human gametes from the same parents, (2^23)^2, produces 70.56 trillion possible combinations of chromosomes that could end up in a zygote - each zygote has a unique genetic identity | 37 | |
| 11592872750 | gametes | sex cells | 38 | |
| 11592872751 | gonads | reproductive glands-male, testes; female, ovaries | 39 | |
| 11592872752 | testosterone | male sex hormone | 40 | |
| 11592872753 | estrogen | female sex hormone | 41 | |
| 11592872754 | haploid | half the normal number of chromosomes | 42 | |
| 11592872755 | Variety of Sexual Life Styles | - the alternation of meiosis and fertilization is a common to all organisms that reproduce sexually; however, the timing of these two events in the life cycle can vary depending on the species | 43 | |
| 11592872756 | Meiosis and Fertilization occur in animals | every generation - there are haploid gametes and a diploid multicellular organism in one generation | 44 | |
| 11592872757 | Plants and some Algae exhibit a second type of life cycle | alternation of generations | 45 | |
| 11592872758 | Alternation of Generates | this type includes both diploid and haploid stages that are multicellular | 46 | |
| 11592872759 | First Generation: Meiosis | - the diploid multicellular sporophyte produces haploid spores by meiosis - each spore grows by mitosis into a haploid multicellular gametophyte sporophyte (2n) -meiosis> spores (n) -mitosis> gametophyte (n) | 47 | |
| 11592872760 | Second Generation : Fertilization | - a haploid gametophyte gives rise to haploid gametes by mitosis - fertilization of two haploid gametes results in a diploid zygote, which develops into the next sporophyte generation gametophyte (n) -mitosis> gametes (n) -fertilization> zygote (2n) | 48 | |
| 11592872761 | Sporophyte | spore-producing plant; the multicellular diploid phase of a plant life cycle |  | 49 |
| 11592872762 | Spores | single-celled reproductive bodies highly resistant to cold and heat damage; capable of new organisms |  | 50 |
| 11592872763 | Gametophyte | gamete-producing plant; multicellular haploid phase of a plant life cycle |  | 51 |
