Presentation on theme: "The continuity of life counts upon the process of reproduction. Parental fees produce a new generation (either single-celled or multicellular) of organisms."— Presentation transcript:

1 The continuity of life relies upon the process of reproduction. Paleas create a new generation (either single-celled or multicellular) of organisms like themselves. Cell cycles develop a bridge in between generations.

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2 Through cell division, a parent cell offers each of its daughter cells through the hereditary instructions (DNA) and cytoplasm required to function on its own. In eukaryotes, the nucleus divides first (in addition to the hereditary material). Then the cytoplasm divides. Tright here are two procedures via which eukaryotic cells have the right to divide: Mitosis Meiosis Prokaryotes divide through binary fission, which is asexual.

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3 This is huguy chromosome #1 Each fifty percent of this chromosome represents sister chromatids. They are joined in the middle by a centromere. Genes are areas on each chromosome that contain hereditary codes for certain hereditary traits Chromosomes are made of DNA DNA is made of Deoxyribose sugar Phosphate group Nitrogenous base Nucleotide Within the nuclear envelope is chromatin…which has DNA, and proteins.

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4 Chromosomes in cells differ in length, form, and which portion of the hereditary instructions they carry. Cells of a given form all contain the exact same number of chromosomes. Diploid cells (2n) contain two of each kind of chromosome. One from mommy, and also one from dad. Haploid cells (n) contain just one of each chromosome. Gametes Somatic

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5 Throughout mitosis the nucleus of the cell divides into two equal nuclei, each with the very same variety of chromosomes as the parent cell. This chromosome number is kept from one generation to the following. Mitosis is responsible for: growth of tproblem repair of tworry cell replacements in multicellular eukaryotes Mitosis is the basis of asex-related remanufacturing in many type of single-celled eukaryotes, as well as prokaryotes.

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6 In interphase, the cell carries out its features. Just before the cell is to divide aobtain, a number of things happen: increases in mass doubles the amount of cytoplasm duplicates each of its chromosomes, and also centrosomes ( each w/2 centrioles ) G1 S G2 Chromosomes are not clearly discerned in the nucleus, although a dark spot referred to as the nucleolus might be visible. The cell might contain a pair of centrioles (or microtubule arranging centers in plants) both of which are business sites for microtubules. (The pair of centrioles together consist of the centrosome)

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7 Mitosis has actually four consistent stages: Early Chromosomes are visible threads. All chromatids twist and fold The nucleolus disappears. Centrioles begin relocating to opposite ends of the cell and fibers extfinish from the centromeres. Some fibers cross the cell to form the mitotic spindle. Late (aka prometaphase) Nuclear envelope breaks dvery own remnants of nuclear envelope create vesicles Microtubules from spindle at each pole press apart. Microtubules affix to one of 2 sister chromatids of each chromosome pair Centromere Centriole

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8 All chromosomes have actually become aligned at the spindle equator At this phase of mitosis, the chromosomes are a lot of tightly condensed.

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9 The sister chromatids of each chromosome pair sepaprice from each various other and relocate to opposite spindle poles. The chromatids are pulled by the microtubules, which are being disassembled Once these sister chromatids are separated, we acknowledge them as chromosomes

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10 As soon as the 2 clusters of chromosomes get to the poles of the cells, telophase gets under way. The chromosomes return to threadlike forms. Vesicles derived from the breakdown of the original nuclear envelope fusage to form patches of membrane about the chromosomes. Once the nuclear membranes are synthesized, and the chromosomes are separated from the cytoplasm, mitosis is complete.

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11 The cytoplasm normally divides at some time in between late anaphase, and also the finish of telophase. Cytokinesis differs considerably depending upon the organism. In animals In pet cells, a cleavage furrow creates In plant cells, a cell plate forms bereason of the cell wall (which isn’t in animal cells) In Plants

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12 Good wellness, and survival itself depends absolutely on the correct timing and also completion of the cell cycle’s events. Genetic disorders may arise from misabsorbs the duplication or distribution of also one chromosome. When normal manage is lost of the cell cycle, and cell department goes unchecked, tissues, and ultimately the organism deserve to be damaged.

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13 Meiosis is equivalent in many kind of methods to mitosis However, in many ways it is different too… Meiosis results in the development of haploid (n) cells.Meiosis outcomes in the development of haploid (n) cells. –In Humans, these are the Ova (egg) and also sperm. –Ova are produced in the ovaries in females –Sperm are produced in the testes of males. –Involves 2 cell departments –Results in 4 cells via 1/2 the normal hereditary information, not identical daughter cells Process called oogenesis Process called spermatogenesis

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14 Meiosis occurs in 2 phases: & Meiosis 2Meiosis occurs in 2 phases: Meiosis 1 & Meiosis 2

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15 Prior to the initially department, the amount of DNA doubles Prior to the first department, the amount of DNA doubles What phase of the mitotic cell cycle would this “doubling” take area in? What stage of interphase would certainly this doubling take place?

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16 the biggest differences in between mitosis and also meiosis take place in prophase I. It is estimated that prophase I accounts for some 85 - 95 percent of the total time for meiosis. Chromosomes condense and also affix to the nuclear envelope Synapsis occurs when a pairing of homologous chromosomes occurs and a tetrad is formed. Each tetrad is composed of 4 chromatids. Crossing over might occur, and also chiasmata become noticeable. Each chromosome gets attached to the spindle in transition to metaphase. Chiasma

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17 All chromosomes are currently positioned at the spindle’s equator. The orientation of the tetrads is random, via either parental homologue on a side. This implies that tbelow is a 50-50 possibility for the daughter cells to get either the mother"s or father"s homologue for each chromosome. As tbelow are 46 chromosomes in human cells, that means that 23 chromosomes finish up on either side. Because of the exadjust in the time of crossing over, these chromosomes are various than they were

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18 Each chromosome is separated from its homologue, and they are moved to opposite poles of the spindle. Chiasmata sepaprice. Chromosomes, each via 2 chromatids, move to sepaprice poles. This is the suggest as soon as many kind of chromosomal abnormalities happen, as a result of incomplete separation. (Nondisjunction)

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19 The cytoplasm of the germ cell divides. Each of the daughter cells is now haploid, but each chromosome still has actually 2 chromatids. Nuclear envelopes may redevelop, or the cell might conveniently start meiosis II.

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20 Meiosis II is the second part of the meiotic process. Much of the process is similar to mitosis and meiosis I. Microtubules have actually moved one member of the centriole pair to the opposite pole of the spindle in each daughter cell. Microtubules connect to the chromosomes, and they are driven towards the spindle’s equator.

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21 Chromosomes are positioned at the spindle equator, midway between the two poles. The kinetochores of the sister chromatids allude towards opposite poles. The kinetochores assemble on the centromere, and are areas responsible for joining the chromosome to the microtubule from the spindle fiber.

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22 The attachment in between the two chromatids of each chromosome breaks. Each of the former sisters, is now a sepaprice chromosome in its own right. (Comparable to anaphase of mitosis)

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23 Distinct nuclei create at the opposite poles and also cytokinesis occurs. At the end of meiosis II, tbelow are 4 daughter cells each through one fifty percent the number of chromosomes of the original parent cell.

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24 In people, primary oocytes complete interphase and prophase I wbelow they are frozen and also reprimary this method till the female reaches puberty. If a woguy is productive on average for 40 years, then 40 X 12 = 580 eggs in her life time. Thus, 400,000 eggs is plenty! A female is born with around 2 million major oocytes. By the moment she reaches puberty, around 400,000 are left (the majority of of them die via the years). This is still method even more than enough!

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25 Of the four haploid cells that create by means of meiosis and also cytoplasmic departments, one or all might develop into gametes and function in sex-related reproduction. Asymmetrical cytokinesis leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated right into the additional oocyte throughout meiosis I, when the secondary oocyte is created. The remaining daughter cells generated from the meiotic events contain fairly bit cytoplasm and also are referred to as polar bodies. Ultimately, the polar bodies degeneprice.

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26 Diploid Haploid, yet copied Haploid

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27 Spermatogonia (precursors to sperm) divide by mitosis to develop even more spermatogonia or spermatocytes. With 22 pairs of autosomes and an average of two crossovers between each pair, tbelow is huge variation among sperm. Meiosis of each spermatocyte produces 4 haploid spermatids. This process takes over three weeks to complete. Then the spermatids create sperm, shedding a lot of of their cytoplasm in the process.

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28 It is approximated that from 10–20% of all huguy fertilized eggs contain chromosome abnormalities, and these are the most widespread reason of pregnancy faiattract (35% of the cases). These chromosome abnormalities: aclimb from errors in meiosis, generally meiosis I; happen more regularly (90%) during egg development than throughout sperm formation; become more regular as a womale periods. Aneuploidy — the gain or loss of whole chromosomes — is the many prevalent chromosome abnormality. It is resulted in by nondisjunction, the faientice of chromosomes to appropriately separate: homologues throughout anaphase of meiosis I sister chromatids in the time of anaphase of meiosis II Zygotes missing one chromosome have monosomy, such as females with a single X chromosome). Three of the same chromosome ("trisomy") is additionally lethal except for chromosomes 13, 18, and also 21 (trisomy 21 is the cause of Down syndrome).


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Three or even more X chromosomes are viable because all but among them are inactivated. Turner’s Syndrome Edward Syndrome Trisomy 18 Klinefelter’s Syndrome

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