How many chromatids are present in each chromosome at the end of meiosis I and II?
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ummmm...well lets see going out on a limb and saying 10
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meiosis has two stages of seperation and it involves sex cells. in the end result of mitosis, you have two identical sister cells, but as a result of meiosis, you end up with 4 daughter cells that are not identical but are similar.
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In G1, there are 46 chromosomes, EACH CONSISTING OF A SINGLE CHROMATID.  You will have two copies of chromosome one (one from mom, the other from dad), two copies of chromosome two, etc.  These pairs are called homologues.  Consequently there are 23 homologous chromosomes in G1 and, again, there is one chromatid per chromosome in this phase.  This gives a total of 46 chromosomes.  You should know that each chromosome is decondensed (not coiled up) at this time. \n\nS phase is the synthesis or replication phase of the cell cycle.  After S phase is complete, the definition of a chromosome changes.  It is now a "replicated chromosome" that consists of 2 chromatids (some texts describe these as "sister chromatids").  Again, the total number of chromosomes is 46; however, because of the definition change of the S-phase chromosome, each chromosome how includes twice as much DNA due to replication.  After S phase there are two chromatids per chromosome.  These chromosomes are decondensed.\n\nIn G2, there are 46 chromosomes:  2 chromatids per chromosome, decondensed, with the chromosomes existing in homologous pairs.\n\nIn prophase of mitosis, the chromosomes condense to facilitate easy separation into the daughter cells.  Here there are still 2 chromatids per chromosome.\n\nIn metaphase, there are STILL 2 chromatids per chromosome, all smartly arranged at the "equator" of the cell, the metaphase plate.\n\nIn anaphase, the replicated chromosomes (i.e., the "sister chromatids") are pulled apart.  At the point that they are separated, the definition of a chromosome changes AGAIN, BACK to a single chromatid.  Each daughter cell will receive 46 of these single chromatids and, therefore, will have 46 chromosomes in 23 homologous pairs.  The chromosomes are still condensed at this point.\n\nIn telophase, the chromosome situation is exactly the same.  23 homologous PAIRS of chromosomes (46 single chromatids).  The difference here is that the chromosomes are now decondensing.\n\nSummary:  the number of chromatids per chromosome\n\nG1-1\nafter S- 2\nG2-2\nprophase-2\nmetaphase-2\nlate anaphase-1\ntelophase-1
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one chromosome comes from each parent
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26\n\nIn meiosis, the chromosome pairs are divided in half so the new cell has 1 of each.  This is because this is used to produce cells for reproduction.\n\nWhen 2 of these cells come together,they create 52 chromosomes again to create a new organism with half of each parents genetic material.
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Let's assume you want a human example.\nHuman cells have 46 chromosomes.\n\nIn Meiosis 1:\nProphase 1- chromosomes replicate, join with homologous pairs to become tetrads.\n--46 chromosomes paired, 23 tetrads, and 92 chromatids\nMetaphase 1- same numbers as prophase\nAnaphase 1: 46 chromosomes (double stranded), 92 chromatids\nTelophase 1: end: 23 chromosomes (double stranded), 46 chromatids per cell\n\nProphase 2: same as Telophase 1\nMetaphase 2: same as Telophase 1\nAnaphase 2: 46 chromosomes, zero chromatids\nTelophase 2: end: 23 chromosomes per cell.
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So in short, sister chromatid are duplicates of the homologous pairs. I hope this helped If so 333 (I) would like the 10 points. :)\n\nThe normal chromosome number in human cells is 46. This number is called a diploid or a 2n number of chromosomes. The chromosomes consist of 23 pairs. Each pair of chromosomes is called a homologous pair. One chromosome of each homologous pair is from the male parent, and the other is from the female parent. The chromosomes of each homologous pair look alike, and they contain genes for the same traits. \n\nSister chromatids are two identical copies of a single chromosome that are connected by a centromere. \n\nFirst, consider mitosis (typical cell division) in a normal diploid cell, with two copies of each chromosome. The chromosomes are duplicated during DNA replication, and the duplicates, called sister chromatids, remain attached to one another until chromosome segregation. Each daughter cell then receives one of the sisters from each homologue pair. Importantly, this means that the daughter cells are exact copies of the mother cell, with two copies of each chromosome, so they can go through the same process again. Thus, we call this process the cell cycle.
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Chromosome Terms before and after DNA Duplication (Replication)\nNote: Duplication and replication mean exactly the same thing.\n• An unduplicated chromosome is one chromosome. A chromosome more or\nless consists of two arms that extend from a narrow "centralized" region called\nthe centromere. The centromere region is often visible when chromosomes\nduplicate.\n• When a chromosome duplicates, it becomes one duplicated chromosome,\nand the two copies remain attached to each other. Note it is still one\nchromosome.\n• The two exact copies of the duplicated chromosome, which remain attached by\nthe protein cohesin, are called "sister" chromatids. They are identical to\neach other. It is essential that you remember this!\n• At the centromere region of the duplicated chromosome, structures (made of\nprotein and DNA) called kinetochores form during division. The three-layered\nkinetochores attach to microtubules of the spindle during mitosis. The\nkinetochores of the two sister chromatids face in opposite directions.\nKinetochore – TEM\n• After the identical sister chromatids are separated during mitosis, each (called\na "daughter" chromosome now) becomes a single unduplicated chromosome\nagain.\nRemember: A chromatid must be attached to its identical chromatid and the two sister\nchromatids comprise one duplicated chromosome. "Sister" chromatids are not two\nchromosomes. They are one duplicated chromosome that consists of two identical\nchromatids. Once sister chromatids are separated they are no longer chromatids!
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B\n\n\nDuring interphase, the chromosomes are found arranged in the nucleus and appear as a network of long, thin threads, called the chromatin
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If we were talking about human cells, there are 23 chromosomes in each cell. In mitosis, there are four main steps with another peparation time. The four are Prophase, Metaphase, Anaphase, and Telephase (PMAT). The peparation time before mitosis is called Interphase (not a step of mitosis) where chromosomes duplicate themselves (23 x 2 = 46 chromosomes total). During these steps of mitosis, the cell divides into two. So if a cell with 46 chromosomes divide into two daughter cells, then each daughter cell will have 23 chromosomes in the end. The result of mitosis: more cells with the same number of chromosomes in each cell.\n\nA cell goes through a cell cycle. Use this link to see the cell cycle: http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells2.html\n\nrelatively, mitosis is a short process.
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Simply put, reduction division is the FIRST division in MEIOSIS in which the number of chromosomes is reduced to half their original number, hence you go from 2N to N, or an example of humans would be 46 to 23 chromosomes, after which there is crossover and you end up with 4 varities in MALES and 2 in FEMALES, one of which will not produce progeny even if fertilized by mistake. Once fertilization between these gametes occurs you end up with 46 chromosomes once again, 23 from each gamete. The production of gametes is called GAMETOGENESIS, which i assume is what you are asking about. Hope that helps!
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normal cell has 23 pairs of chromosomes (46 chromatids)\nbefore mitotic division the number doubles to 46 pairs (92 chromatids) the chromosomes are arranged as sister chromatids joined by the centromere and aligned with their copies (this is where recombination events can take place). the pairs are then pulled apart and separated in to the two new cells (each with 23 pairs). \n\nNote: for meiotic division (production of gametes (sperm and egg)) 23 pairs of chromosomes are divided in to 2 lots of 23 single chromosomes.
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During prophase 1 of meiosis, the chromosomes have duplicated and have joined with their homologous pair to form a 4 stranded tetrad.\n\nBecause you get one chromosome in each homologous pair from your mother and one from your father, although they code for the same concepts, they may code slightly differently (ie blue eyes vs brown eyes).\n\nTo exchange genetic material, during prophase one the two chromatids closest together in the tetrad (one from each mom and dad- the outer two are too far away to do this, so they remain untouched) "cross over".  Literally, the ends of the chromatids cross each other and bits of the chromosomes break off of one and reattach on the other, giving genetic variability.\n\nOk, so for example: the chromosome your mother gave you coded for blue eyes, blonde hair, curly hair, and long fingers.\nThe chromosome from your father codes for the same principles, just differently- say brown eyes, red hair, straight hair and short fingers.\n\nSo crossing over between these two occur in prophase 1, and some codes are swapped.\n\nNow we have a tetrad (4 chromatids) that code for the following.\n(We'll say the chromosome from mother is on the left and from father is on the right)\nStarting with the leftmost and going to the rightmost:\nChromatid 1 codes for: \n-blue eyes, blonde hair, curly hair, and long fingers\nChromatid 2 codes for:\n-blue eyes, brown hair, curly hair, and short fingers.\nChromatid 3 codes for:\n-brown eyes, blonde hair, straight hair, and long fingers\nChromatid 4 codes for:\n-brown eyes, brown hair, straight hair and short fingers.\n\nSo now we have the genetic variability, and 4 completely unique chromatids, that are still homologous pairs, just giving us four different codings for the same traits.\n\nHope this helps.
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The beginning of somatic cell division or mitosis is called prophase. In early prophase, the centrosomes move toward opposite poles of the cell, organizing the spindle microtubules between them. The sister chromatids become visible in the nucleus as they condense.In late prophase, the nuclear membrane breaks down and some of the spindle microtubules attach to the sister chromatids. The microtubules pull the chromatid pairs to the midline of the cell, or metaphase plate.The chromatids remain lined up between the poles of the cell during metaphase.Anaphase begins when the pairs of sister chromatids separate. The separated chromatids are now called chromosomes, and move toward the poles of the cell.The chromosomes arrive at the poles in telophase, and new nuclear membranes form around them.Division of the cytoplasmic components is called cytokinesis.In animal cells, cytokinesis occurs when a ring of actin and myosin filaments constricts the plasma membrane at the equator. Eventually, the parent cell is divided into two cells.Meiosis I-Prophase I-In 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.The 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.The 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.During 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.Chromosomes 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.During 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.Microtubules 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.Metaphase I-As kinetochore microtubules from both centrioles attach to their respective kinetochores, the homologous chromosomes align equidistant above and below an imaginary equatorial plane, due to cont
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Two, one in each phase of meiosis (I and II).\nBut the textbook can tell you that, my advice is you try and understand how it works.
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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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Normal male cells have 23 pairs of chromosomes (1-22 & X+Y) or 46 total chromosomes.