Homologous Chromosomes and Sister Chromatids

Topics: Meiosis, Genetics, Gene Pages: 6 (1862 words) Published: November 24, 2014

Homologous Chromosomes and Sister Chromatids (HC and SC): Clearly distinguish between HC and SC pairs. Your answer should include the following: a clear distinction between ‘chromatin’ and ‘chromosome’, and how this difference affects gene expression; simple line diagrams to illustrate the difference between non-replicated and replicated DNA inchromatin and chromosome forms; afull description of both HC and SC with a labeled diagram that includes gene/allele sequences for a heterozygote and ‘m’ or ‘p’ labels to indicate parental origin; a definition of diploid and haploid cells in terms of HC content; an explanation of

the stage of the organism’s life cycle at which the HCfirst come into existence(I am NOT asking for when they are first visible as a pairduring the cell cycle),and the stage of the cell cycle at which SCform (again, not when they are first visible); a description of the differences between what happens to HC and SC during mitosis and meiosis I and meiosis II (please do not diagram out each stage, just describe the 2-3 key differences between the events of mitosis and meiosis I & II that explain the different outcomes); and an explanation of how these differences relate to the different functions of mitosis and meiosis in the organism.

A chromatin is DNA combined with proteins that is found in the nucleus of eukaryotic cell, It is partially compacted. A chromosome is a fully compacted chromatin that is visible in cells during nuclear division. the degree to which chromatin is compacted greaty affects the accessbility of chromatin to the cell because compaton is necessary in order to fit a very large amount of DNA into a much smaller nucleus. Homologous chromosomes are two chromosomes with the same length, centromere position and same sequence of genes because they are the same chromosome type. Not same alleles because one maternal and one paternal, they are never attached by the centromere and appear in metaphase, so they are replicated. Sister chromatids are one half of a replicated chromosome, which contains 2 daughter DNA molecules that is made during s-phase. They are identical in both gene and allele sequence because that are produced by the same DNA molecule and are always connected at the centromere. Diploid are the number of chromosomes in a body cell, characteristic of a species. Always an even number because chromosomes are in pairs. Homologous chromosomes (M and P) are present for each chromosome type. Haploid is the number of chromosomes in a gamete, its one half of the diploid number but not just any half. One chromosome, onl of each type present (m or p). when two haploid cells fuse it creates a diploid. interphase is the stage of the cell cycle at which sister chromatids form mitosis occurs in all cells and results in two diploid cells, they do not pair up or cross over. only goes through one division. the 2 daughter cells are identical cells with 46 chromosomes each. meiosis occurs in humans, animals, plants and fungi. results in 4 haploid cells with 23 chromosomes each and goes through 2 divisions. they are more diverse during meiosis because crossing and independent assortment. because there is more genetic diversity in sex cells they are used for reproduction for diverse indivduals whereas mitosis is used to replicate and produce identical cells for growth and repair.

The Importance of Meiosis: meiosis is different from mitosis in a number of ways. Address the following bullets to explain the unique features of meiosis and their relationship to sexual reproduction. Explain the role of meiosis in sexual reproduction. Is meiosis the same as sexual reproduction or is it just part of the process? If it is just part of the process, what else is needed to complete sexual reproduction? Diagram the meiotic cell cycle, labeling all phases of the cycle. Note: you are NOT being asked to make diagrams of each phase, just of the pie chart of the cycle. Draw all the forms ONE...
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