Which of the following terms identifies a constricted region on the chromosome to which microtroubles bring du
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The centromere is the region where the condensed sister chromatids are joined and constricted. The Spindle fibers (formed from microtubules of the cytoskeleton that are temporarily broken up and reassembled) attach to the kinetochore (a protein) that is around the centromere. The bringing du part i don't understand.\n\nHope this helps and best of luck.
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The small, dark region in the cell nucleus is indeed called the nucleolus.  It is thought to be the site of ribosome synthesis.
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D is definitely the false answer because, in Meiosis I, the homologous chromosomes are seperated. The chromosomes are divided in Meiosis II. The seperating of the two homologous chromosomes into different daughter cells cause the number of chromosomes to be halved.\n\nE is definitely correct because the daughter cells are different from each other due to cross-over and also because of the seperation of homologous chromosomes.
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In the "classic" (depicted) karyotype, a dye, often Giemsa (G-banding), less frequently Quinacrine, is used to stain bands on the chromosomes. Giemsa is specific for the phosphate groups of DNA. Quinacrine binds to the adenine-thymine-rich regions. Each chromosome has a characteristic banding pattern that helps to identify them; both chromosomes in a pair will have the same banding pattern.\n\nKaryotypes are arranged with the short arm of the chromosome on top, and the long arm on the bottom. Some karyotypes call the short and long arms p and q, respectively. In addition, the differently stained regions and sub-regions are given numerical designations from proximal to distal on the chromosome arms. For example, Cri du chat syndrome involves a deletion on the short arm of chromosome 5. It is written as 46,XX,5p-. The critical region for this syndrome is deletion of 15.2, which is written as 46,XX,del(5)(p15.2).[1]\n\n\n[edit] Spectral karyotype (SKY technique)\n Spectral karyotype of a human femaleSpectral karyotyping is a molecular cytogenetic technique used to simultaneously visualize all the pairs of chromosomes in an organism in different colors. Fluorescently-labeled probes for each chromosome are made by labeling chromosome-specific DNA with different fluorophores. Because there are a limited number of spectrally-distinct fluorophores, a combinatorial labeling method is used to generate many different colors. Spectral differences generated by combinatorial labeling are captured and analyzed by using an interferometer attached to a fluorescence microscope. Image processing software then assigns a pseudo color to each spectrally different combination, allowing the visualization of the individually colored chromosomes.[2]\n\nThis technique is used to identify structural chromosome aberrations in cancer cells and other disease conditions when Geimsa banding or other techniques are not accurate enough.
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Prophase I\nIn the leptotene stage, the cell's genetic material, which is normally in a loosely arranged pile known as chromatin, condenses into visible threadlike structures. Along the thread, centromeres are visible as small beads of tightly coiled chromatin. Recall that centromeres are connection sites between sister chromatids, which are not yet distinguishable. As the chromatin becomes progressively ordered and visible, homologous chromosomes find each other and bind together. In this process, called synapsis, a protein structure called the synaptonemal complex attaches the homologous chromosomes tightly together all along their lengths.\n\nThe zygotene stage sees the completion of synapsis. The paired homologous chromosomes are said to be bivalent. They may also be referred to as a tetrad, a reference to the four sister chromatids. During this stage, one percent of DNA that wasn't replicated during S phase is replicated. The significance of this cleanup act is unclear.\n\nThe pachytene stage heralds crossing over. Nonsister chromatids of homologous chromosomes exchange segments of genetic information. Because the chromosomes cannot be distinguished in the synaptonemal complex, the actual act of crossing over is not perceivable through the microscope.\n\nDuring the diplotene stage, the synaptonemal complex degrades. Homologous chromosomes fall apart and begin to repel each other. The chromosomes themselves uncoil a bit, allowing some transcription of DNA. They are held together by virtue of recombination nodules, betraying the sites of previous crossing over, the chiasmata.\n\nChromosomes recondense during the diakinesis stage. Sites of crossing over entangle together, effectively overlapping, making chiasmata clearly visible. In general, every chromosome will have crossed over at least once. The nucleoli disappears and the nuclear membrane disintegrates into vesicles.\n\nDuring these stages, centrioles are migrating to the two poles of the cell. These centrioles, which were duplicated during interphase, function as microtubule coordinating centers. Centrioles sprout microtubules, essentially cellular ropes and poles, during crossing over. They invade the nuclear membrane after it disintegrates, attaching to the chromosomes at the kinetochore. The kinetochore functions as a motor, pulling the chromosome along the attached microtubule toward the originating centriole, like a train on a track. There are two kinetochores on each tetrad, one for each centrosome. Prophase I is the longest phase in meiosis.\n\nMicrotubules that attach to the kinetochores are known as kinetochore microtubules. Other microtubules will interact with microtubules from the opposite centriole. These are called nonkinetochore microtubules
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Its b.\nindependent assortment in meiosis
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sex-linked genes which can still be classified into x-linked genes and y-linked genes... ;p
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gonosomes.    which are the sex chromosomes ! Hope this is it !! :o)
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a group of lines that are genetically identical except at one or a few loci.
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This may seem like a silly suggestion, but try representing the elements mentioned in your textbook (which I'm sure has some illustrations) with pieces of paper, matches, beans or something like that, so you can understand the events and the outcome. \nNow, if you _really_ want an explanation, here it comes (I've ommited the names of the phases, they'll be in your textbook).\n\nMeiosis includes 2 cell divisions with different characteristics. \nWe start with a diploid (2 n) cell, in which DNA duplication has occurred so that each DNA strand is double. These strands do not yet appear as chromosomes (condensed bodies); in fact, the chromatin strands have to be "relaxed" in order to duplicate. \n\n***Meiosis I: (in which the nº of chromosomes decreases to half)\n1. The chromatin (DNA strands) starts to condense and appears as small dense dots (the chromosomes) within the cell nucleus. These chromosomes will each have 2 "arms" (they look like an X or a V) because the DNA in each has been duplicated.\n2. Now all these chromosomes align in homologous pairs, with the aid of a transparent structure formed by tiny intracellular fibers (the spindle) that has formed and will help them to move in orderly fashion within the nucleus.\n3. While they keep condensing, each homologous chromosome contacts its "brother", and they exchange some fragments of their DNA ("crossing over"). Usually only one "arm" of each  chromosome participates in crossing over. \n4. In the meantime, the nuclear membrane is disintegrating...\n5. The pairs of homologues, still united, align at the middle (equator) of the spindle... \n6... and then each pair of homologues is divided, one chromosome of each pair goes toward each "pole" of the spindle. \n7. New nuclear membranes form around the 2 groups of chromosomes. Each of these groups will only have ONE of each pair of homologues. Essentially the information in each new nucleus is the same, BUT has some differences because, as you recall, there has been crossing over i.e. partial exchange of DNA between homologues. \n8. The original cell with the 2 nuclei divides and forms 2 cells, with half the nº of chromosomes of the original cell (haploid or n). Each of the chromosomes still has a duplicate DNA strand.\n\n... the cell takes a short break (you can take a break too!)... but the chromatin does not duplicate this time (it's already done that)\n\n***Meiosis II: (in which each double DNA strand becomes single again, this phase is similar to a normal mitosis).\n1. The chromatin condenses again, so that it appears as chromosomes.\n2. This time the spindle aligns the center of each chromosome at its equator.\n3. The central part of the chromosome is duplicated and the sister "arms" (chromatids) separate, each migrating to opposite poles.\n4. Now you have two groups of chromosomes, each group still has the haploid (n) nº of chromosomes (the same amount with which they started this 2nd meiosis) but now, each chromosome has a single DNA strand. \nA new nuclear membrane forms around each of these groups of chromosomes.\n5. The rest of the cell divides.\n\nSo, to sum up: you started with ONE diploid cell. You end with FOUR haploid cells. In animals, this process only happens during the production of gametes. \nIf we're talking about the formation of female gametes, then only ONE of the 4 resulting cells will become an ovule (and that only after more maturation), the other 3 cells form "polar bodies".\nIn contrast, when it's spermatozoids being produced, all FOUR resulting cells will become spermatozoids. \nThat's one of the reasons sperm is cheaper than ovules! There's just more of them in the entire animal kingdom.\n\nNow, what is the purpose of this extremely complicated (the above is a very simplified version) process? The result will be cells that have half the chromosomes of the normal body cells. These cells
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Cross overs happen between gene locations furthur because there is more distance between to for the chromosomes to touch and cross. If they are closer, there is less area for these chromosomes to touch and exchange genetic information. 1 map unit = about 1% cross overs. If something is 10 map units appart, there is about 10% crosss over and 20 = 20% and so on. If you think about it, its like fighting with two swords. say one gene is at the tip and the other is at the handle (far genes). The chances of your opponent hitting your sword in that region is more likely than between the the tip and 1 inch down from it (close genes).
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At the time of cell division only the chromatid number doubles.Inter phase is the resting phase intht phase no doubling tales place .It takes place at the early meta phase stage\nIn anaphase the polar fibers or spindle fibers get attached to chromosome near the centromere.Then while they are moving towars poles,each centromere splits and carries half chromosome or one  chromatid.The chromatid in telophase becomes a full chromosome\nSo 46 chromosoes become 92 and 92become 46at the end of telophase stage.Hope you got the point.
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one chromosome comes from each parent
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Karyotype\n\n(FISH (Fluorescent In Situ Hybridization) can also be used if visualization of certain regions on specific chromosomes is desired.)
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cell, chromosome, gene, nucleotides, base subunit, atom, nucleus\n(biggest to smallest)\n\ndepending on the question referring to the atomic nucleus not the cellular one\n\nif it referrs to the cellular nucleus it is smaller than cell, bigger than chromosome
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I think the answer to your question lies in the fact that some of the DNA is "wound" tighter than other sections along the chromosome.  \n\nThe tightly wound DNA is typically not transcribed in somatic cells (it might be a different story for germ line chromosomes, or chromosomes from embryonic tissue, and even stem cells for that matter).\n\nWhen a gene is constantly being transcribed, say for example genes for hemoglobin, the cell prefers to keep the region open for easy access.  It can do so by acetylation of histone molecules.  \n\nWhen histone is not acetylated, then the molecule keep the chromosome wrapped up tight.  \n\nWhen the dye attaches to the chromosome, tightly packaged DNA appears darker because there is a high concentration of dye in that smaller surface area.  \n\nSo staining helps identify euchromatin (actively transcribed DNA sequence, stains lighter) and heterochromatin ("inactive" DNA sequence, stains darker).\n\nThe dye has the propensity to stain both types of chromatin equally.  But it's the density of the dye which makes it appear darker or lighter.\n\nIt was fun thinking about your question.  Pass on the good karma!
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check out this link.\nenjoy.\nhttp://gslc.genetics.utah.edu/units/activities/extraction/