Thank you for all the answers! Yes a normal human should have 23 chromosomes but unfortunately during meiosis undisjunction may occur. What if a person that has 47 chromosomes, which is a person with down syndrome, has an extra chromosome 21. How do you determine the sex of this person?
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Well if the non-disjunction is for an autosome and leads to trisomy (the presence of a homologous pair + 1 more of a chromosome) as happens in down's syndrome for chromosome 21 it leads to abnormalities but has no effect on sex (gender should we say? for sex i imagine would be severely effected)\nGender is only effected when the chromosomal non disjunction happens to the sex chromosomes leading to the XO, XXX, XXY states which cause various diseased or intersex cxonditions.
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Probably has to do with x & Y chromosomes has to do with genetics to make baby a boy or girl
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The 46, XX male syndrome is a rare sex chromosomal disorder in man [1]. It mostly occurs due to unequal crossing over between X and Y chromosomes during meiosis [2]. A 32 year old XX male with normal male phenotype and normal adrenarchal hair pattern, bilateral atrophic testes, normal phallus presented with azoospermia and infertility. The gonadotrophins were elevated. Cytogenetic and molecular analysis using FISH with X and SRY probe showed a 46,XX (SRY negative) chromosomal constitution.\n\nDefinition:\nXX male syndrome occurs when the affected individual appears as a normal male, but has female chromosomes. Two types of XX male syndrome can occur: those with detectable SRY gene and those without detectable SRY (Sex determining region Y). SRY is the main genetic switch for determining that a developing embryo will become male.\n\nDescription:\nXX male syndrome is a condition in which the sex chromosomes of an individual do not agree with the physical sex of the affected person. Normally there are 46 chromosomes, or 23 pairs of chromosomes, in each cell. The first 22 pairs are the same in men and women. The last pair, the sex chromosomes, is two X chromosomes in females (XX) and an X and a Y chromosome in males (XY).\n\nIn XX male syndrome, the person has female chromosomes but male physical features. The majority of persons with XX male syndrome have the Y chromosome gene SRY attached to one of their X chromosomes. The rest of the individuals with XX male syndrome do not have SRY detectable in their cells. Hence, other genes on other chromosomes in the pathway for determining sex must be responsible for their male physical features.\n\nGenetic profile:\nIn XX male syndrome caused by the gene SRY, a translocation between the X chromosome and Y chromosome causes the condition. A translocation occurs when part of one chromosome breaks off and switches places with part of another chromosome. In XX male syndrome, the tip of the Y chromosome that includes SRY is translocated to the X chromosome. As a result, an embryo with XX chromosomes with a translocated SRY gene will develop the physical characteristics of a male. Typically, a piece of the Y chromosome in the pseudoautosomal region exchanges with the tip of the X chromosome. In XX male syndrome, this crossover includes the SRY portion of the Y.\n\nIn individuals with XX male syndrome who do not have an SRY gene detectable in their cells, the cause of the condition is not known. Scientists believe that one or more genes that are involved in the development of the sex of an embryo are mutated or altered and cause physical male characteristics in a chromosomally female person. These genes could be located on the X chromosome or on one of the 22 pairs of autosomes that males and females have in common. As of 2001, no genes have been found to explain the female to male sex reversal in people affected with XX male syndrome who are SRY negative. Approximately 20% of XX males do not have a known cause and are SRY negative. It is thought that SRY is a switch point, and the protein that is made by SRY regulates the activity of one or more genes (likely on an autosomal chromosome) that contribute to sex development. Also there have been some studies that demonstrate autosomal recessive and autosomal dominant inheritance for the XX male.\n\nDemographics:\nXX male syndrome occurs in approximately one in 20,000 to one in 25,000 individuals. The vast majority, about 90%, has SRY detectable in their cells. The remaining 10% are SRY negative, although some research indicates that up to 20% can be SRY negative. XX male syndrome can occur in any ethnic background and usually occurs as a sporadic event, not inherited from the person's mother of father. However, some exceptions of more than one affected family member have been reported.\n\nSigns and symptoms:\n\nSRY positive XX male syndrome\nMales with SRY positive XX male syndrome look like and identify as males. They have normal male physic
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The mechanism for an abnormal amount of X or Y is called nondisjunction in meiosis of cellular division. However there is no possible way for a man to father only one gender.\n\nHaving only a Y is not enough DNA for viable offspring, so the gamete automatically aborts.\n\nHaving only an X results in a female with a condition called Turner's Syndrome. This will not cause a phenomenon of having only boys or only girls because the female does not choose the gender anyway.\n\nThe only possible way for a man to have a higher possibility of having boys is if he has an extra Y chromosome (XYY) caused by nondisjunction. Then the chances that the offspring is a girl is 33% and the chances of having a boy is 67%.\n\nAnd in case you were wondering, a male with XYY has Kleinfelter's syndrome and is infertile.\n\nAlso, you're saying that you have examples from literature, which may not be reality. It's highly unlikely that a father has 15 children of the same gender. I'd say literature tends to exagerate :)
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hmm always thought there were more girls than guys in this world, never really thought about it, but according the the current theories behind genes, there should be an equal chance between recieving the chromosomes for a boy as a girl.
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First off, the effects of the X and Y genes aren't "averaged out" but rather regulated.  A female does have two X chromosomes, but the genes on those chromosomes are being regulated by protein production which is regulated by hormones.  Basically what is happening is that the female cell is recognizing that there are two copies of a certain gene (like one on the X chromosome) and it down regulates this gene, essentially terminating its transcription.  A "normal" male however, only has one X chromosome and therefor the genes on this chromosome must be upreguated to produce enough gene product.  Earlier I said "normal" male meaning one with XY genotype, this is because you can have other genotypes such as XYY.  The sex of an individual on the genomic level is determined by the RATIO of sex chromosomes to autosomes, not neccesarily the number of chromosomes.  \nFurthermore, a males body is built with larger thicker bones that allow for more muscle mass.  The physiological composition of a female just doesn't allow for the gain of that much muscle.  For example you can use a toothpick to pick up a cocktail weenie, the same toothpick would surely break if you tried picking up a steak... It's just too much mass for the small structure.  \nHope this helps!
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Meiosis consists of 2 nuclear divisions that reduce the # of chromosomes to the haploid # (n) in preparing for sexual reproduction. \n\nThe fertilization of the haploid cells, sperm and ova (gametes), is the diploid cell (zygote) which gives a 50% chance of daughter cells being maternal or paternal for each chromosome. not sure on the 1/8 chance of paternal chromosomes.\n\n# of possible combinations = 2 to the nth power (2 ^n)\nso, if 2n=6, then n=3 and there is 2 ^3 = 8 number of combinations.\n\nJust FYI, In humans with 23 pairs of chromosomes, a gamete  could have 2^23 or 8,388,604 possible combinations of chromosomes from that parent. Any couple could have 2^23 ×  2^23 or 70 trillion different possible children, based just on the number of chromosomes. \n\nIn addition, crossing-over, in which the two homologous chromosomes of a pair exchange equal segments during synapsis in Meiosis I, can add further variation to an individual’s genetic make-up.
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Gametes are produced via meiosis\n\nThe chromosomes are seperated into two and go to their respective cells.\n\nMeiosis divides the genetic material in a normal cell if half. A normal cell has 46 chromosomes, a gamete has 23.\n\nTwo gametes combine during infertilization creating a zygot so to grow into a fetus.
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Unless I'm mistaken, I'm afraid there are no treatments for trisomic conditions except relieving symptoms.\n\nThis is a mosaic condition, though, which means that the extra chromosome 9 is not present in all cells, so the severity of the symptoms will depend on the proportion of cells that are abnormal.
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Why all these people are saying its 50/50 I have no idea.  It certainly is NOT 50/50, the chance varies for every individual.  Some males have more sperm with the X chromosome and some have more sperm with the Y chromosome.  Very few, if any, males have an exact 50/50 ratio.
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Men typically have one X chromosome and one Y chromosome in each diploid cell of their bodies. Women typically have two X chromosomes.
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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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Each chromosome within our body (except the chromosomes within cells that develop into sperm or eggs) is created by making a copy of a previously existing chromosome. This occurs during the process called mitosis, during which cells divide for growth or repair. Before each division, the cell makes an identical copy of each chromosome and during mitosis, each of the two new cells receives a complete set of 46 chromosomes.\n\nEach new cell has the same set of chromosomes and the same genetic information as the "parent" cell. This explains why almost every cell in your body has the same genetic information.\n\nA slightly different process takes place during the production of egg and sperm cells. When an egg and a sperm unite at fertilization, their nuclei unite to form the nucleus of a human zygote. If the sperm and egg carried 46 chromosomes, like the rest of the body's cells, then the zygote would have 92, which would be incompatible with life. \n\n\nTo prevent this, a special type of cell division, called meiosis, takes place. \n\nThe process of meiosis begins with a single cell containing 46 chromosomes and results in four reproductive cells (sperm or eggs), each of which carries 23 chromosomes. An important feature of these four cells is that the combination of genes they carry on their 23 chromosomes is a unique mix of the genes present in the original single cell. \nYou resemble your parents because half of the instructions — genes — for making you came from your father and half from your mother. Similarly, your brother or sister also received half of their genetic instructions from each parent, but the set they received is somewhat different from the set you received. That's why they may resemble you, but they are not identical to you. Identical twins receive exactly the same combination of genes and chromosomes.
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C... a boy would have XY chromosomes and a female would have XX chromosomes.  Y is always smaller than X.
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Nondisjunction occurs during meiosis (cell division that produces gametes), specifically anaphase I. Normally, homologous chromosome pairs are lined up in the middle during metaphase I and are seperated from one another in anaphase I, a process called disjunction. However when this process does not occur, both chromosomes in the pair are carried together to the same pole of the cell, resulting in one cell having too many chromosomes and the other having too few. This can lead to genetic disorders, such as Down's syndrome (aka trisomy 21 - 3 copies of chromosome 21). Hope this helps!
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all normal males are XY.  all normal females are XX.  the female always donates 1 X chromosome to the offspring.  the male donates either an X or a Y to the offspring (50% chance of each event).  If the male donates an X, the offspring will be XX and female.  if the male donates a Y, the offspring will be XY and male.
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In Turner syndrome, the girl does not have the usual pair of two complete X chromosomes. The most common scenario is that the girl has only one X chromosome in her cells. Some girls with Turner syndrome do have two X chromosomes, but one of the X chromosomes is incomplete. In another scenario, the girl has some cells in her body with two X chromosomes, but other cells have only one.