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| reproduction in which all offspring inherit the same number and kinds of genes from a single parent. |
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| sequences of chromosomal DNA |
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| process involving meiosis, formation of gametes, and fertilization(union of two gametes.) |
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| unique molecular form of the same gene |
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| sum of total chromosomes in cells of a given type |
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| a pair of each type of chromosome, often from two parents. |
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Each pair has same length, shape, and assortment of genes.
hom- means alike. |
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| meiosis reduces the parental chromosome number by half; 46 chromosomes to 23 chromosomes |
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| two attatched DNA molecules and associated proteins sister chromatids |
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| cell forms from male and female gametes. Chromosomes go throught two consecutive divisions that end with formation of four haploid nuclei. |
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Interphase-DNA is replicated prior to meiosis 1
Prophase 1, Metaphase 1, Anaphase 1, Telophase 1.
Chromosomes align with partner, homologue to homologue, then the partners seperate and two haploid daughter cells are formed, with one of each type of chromosome. |
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No interphase stage
Prohpase II, Metaphase II, Anaphase II, Telophase II.
The two sister chromatids of each chromosme are seperated. There are now four parcels of 23 chromosomes, each with one chromosome of each type. Nuclear envelopes surround them to create four nuclei, which the cytoplasm divides once more, so the outcome is four haploid cells. |
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| Each chromosome pairs with its homologue and usually swaps segments with it. Microtubules are forming a spindle and nuclear envelope is starting to break up. |
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| microtubules form the spindle poles tether with each type of chromosome. Chromosomes all align midway between the poles. |
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| microtubules attached to each chromosome shorten and move it toward a spindle pole. Other microtubules extending from the poles ratchet past each other, drove by mototr proteins, and push the two poles farther apart. |
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| one of each type of chromosome arrives at a spindle pole. The cytoplasm divides at some point, forming two haploid cells. Chromosomes are still duplicated |
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| Bipolar spindle forms in each haploid cell. One member of centriole pairs has been moved to opposite end of cell by microtubules. One chromatid of each chromosome becomes tethered to one spindle pole, and its sister chromatid becomes tethered to the opposite pole. |
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| microtubules from both poles have assemebled and disassembled, and chromosomes are positioned midway between the poles. |
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| Attatchment of sister chromatids break and each becomes a seperate chromosome still tethered to microtubules, which move it towards a spindle pole; while, other microtubules push the poles apart. A parcel with one type of each chromosome ends up near each pole. |
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| four nuclei form as a new nuclear envelope encloses each cluster of chromosomes. After the cytoplasm divides, each resulting daghter cell has a haploid number of chromsomes. |
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a molecular interaction between a chromatid of one chromosome and a chromatid of the homologous partner, occuring during prophase 1.
It leads to recombinations among genes of homologous chromsomes and eventually to variation in traits among offspring. |
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| a haploid reproductive cell that is not a gamete and does not take part in fertilization. Produced by a sporophyte. |
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| a type of mature male gamete |
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| the mature female gamete (ovum) |
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| gamete formation in males |
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| In male reproductive system, a germ cell develops into a primary spermatocyte which enters meiosis and cytoplasmic divisions and four haploid cells develop into spermatids, which undergo changes and develop into a sperm. |
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| gamete formation in females |
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| in female reproductive system a germ cell becomes a primary oocyte which increases in size and cytoplasmic components. Its four daughter cells differ in size and function. After meiosis 1, one daughter cell (secondary oocyte) gets nearly all of the cytoplasm . After meiosis II and cytoplasmic division, one daughter cell develops into a gamete, known as an egg. |
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when a female and male gamete unite and their haploid nuclei fuse, adding to variation among offspring.
If fertilization didn't occur after meiosis, chromosome number would double in each generation. |
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