question: How are some people born female, but have male XY chromosomes?
comment: Hey I remember this from a college-level Sex class I had! There are a variety of chromosome disorders that can occur, such as XX males, XY females, XXY males (also known as Kleinfelter's Syndrome), and more. And within those, there can be a lot of variation as well about how it specifically affects each individual. These disorders occur during development of the fetus, and while rare, are apparently quite random (thats what we were told), so we don't know exactly why they occur. Just a note, most people affected with one of these are infertile, and may have deformities (again depending on the specifics) of both internal and/or external sexual and reproductive parts. Some persons may be classified as intersex, or self identify as such, although many will consider themselves male or female as well, are generally are raised as such and identify as such. For people affected by one of these disorders, they are (sometimes not willingly as children) often given treatments to help develop in a certain way, such as to boost testosterone for males or for females to start their period, in order to help their body into puberty, which may be delayed or not occur in some cases without external help. Again I should reiterate, as we were told, these don't affect each person identically, although there are traits that are fairly universal within each disorder, each person may or may not have the exact same situation and/or issues-- our professor made it a point to keep calling this out to explain that each person really is their own case and there is no "perfect" answer for everyone regarding both physically and mentally
passages: All animals have a set of DNA coding for genes present on chromosomes. In humans, most mammals, and some other species, two of the chromosomes, called the X chromosome and Y chromosome, code for sex. In these species, one or more genes are present on their Y chromosome that determine maleness. In this process, an X chromosome and a Y chromosome act to determine the sex of offspring, often due to genes located on the Y chromosome that code for maleness. Offspring have two sex chromosomes: an offspring with two X chromosomes will develop female characteristics, and an offspring with an X and a Y chromosome will develop male characteristics.
   Chromosomal abnormalities can occur during fertilization impacting the development of the male reproductive system. The genotype of the male consists of a Y chromosome paired with an X chromosome. Female gender is determined by the absence of a Y chromosome. Some individuals are male who have the XX male syndrome and androgen insensitivity syndrome. This occurs when one X chromosome contains a segment of the Y chromosome, which was inserted into the X chromosome of the father's sperm. Rarely females are born with the XY genotype. They are found to be missing the same portion of the Y chromosome it was inserted into the chromosome of XX males. The gene for sexual differentiation in humans, called the testis determining factor (TDF), is located on the short arm of the Y chromosome. The presence or absence of the Y chromosome determines whether the embryo will have testes or ovaries. An abnormal number of sex chromosomes (aneuploidy) may can occur. This includes Turner's syndrome - a single X chromosome is present, Klinefelter's syndrome - two X chromosomes and a Y chromosome are present, XYY syndrome and XXYY syndrome. Other less common chromosomal arrangements include: triple X syndrome, 48, XXXX, and 49, XXXXX. 
   Allosomes not only carry the genes that determine male and female traits, but also those for some other characteristics as well. Genes that are carried by either sex chromosome are said to be sex linked. Sex linked diseases are passed down through families through one of the X or Y chromosomes. Since only men inherit Y chromosomes, they are the only ones to inherit Y-linked traits. Men and women can get the X-linked ones since both inherit X chromosomes. 
   BULLET::::- XYY syndrome. XYY boys are usually taller than their siblings. Like XXY boys and XXX girls, they are more likely to have learning difficulties.
  
  Section::::Aberrations.:Sperm aneuploidy.
  
  Exposure of males to certain lifestyle, environmental and/or occupational hazards may increase the risk of aneuploid spermatozoa. In particular, risk of aneuploidy is increased by tobacco smoking, and occupational exposure to benzene, insecticides, and perfluorinated compounds. Increased aneuploidy is often associated with increased DNA damage in spermatozoa.
  
  Section::::See also.
  
  BULLET::::- Aneuploidy
  
  BULLET::::- Chromosome segregation
  
  BULLET::::- DNA
  
  BULLET::::- Genetic deletion
  
  BULLET::::- For information about chromosomes in genetic algorithms, see chromosome (genetic algorithm)
   The sex chromosome in a human egg is always an X chromosome, since a female only has X sex chromosomes. In sperm, about half the sperm have an X chromosome and half have a Y chromosome. If an egg fuses with a sperm with a Y chromosome, the resulting individual is male. If an egg fuses with a sperm with an X chromosome, the resulting individual is female. There are rare exceptions to this rule in which, for example, XX individuals develop as males or XY individuals develop as females. Chromosomes are not the final determinant of sex. In some cases, for example, chromosomally female babies that have been exposed to high levels of androgens before birth can develop masculinized genitals by the time they are born. There are other variations of sex chromosomes that lead to a variety of different physical expressions.
   Like most other male mammals, a man's genome typically inherits an X chromosome from his mother and a Y chromosome from his father. The male fetus produces larger amounts of androgens and smaller amounts of estrogens than a female fetus. This difference in the relative amounts of these sex steroids is largely responsible for the physiological differences that distinguish men from women. During puberty, hormones which stimulate androgen production result in the development of secondary sexual characteristics, thus exhibiting greater differences between the sexes. However, there are exceptions to the above for some transgender and intersex men.
  
  Section::::Etymology and terminology.
   Section::::Sexual Expression.
  
  The system for determining sex in "Silene latifolia" is close to that found in humans because in both cases the Y chromosome determines what reproductive mechanisms will be expressed in the offspring. They differ because there are multiple sex determining genes on the Y chromosome of "S. latifolia", while in humans the presence or absence of the Y chromosome strictly determines whether the offspring is male or female.
   The human genome consists of two copies of each of 23 chromosomes (a total of 46). One set of 23 comes from the mother and one set comes from the father. Of these 23 pairs of chromosomes, 22 are autosomes, and one is a sex chromosome. There are two kinds of sex chromosomes–"X" and "Y". In humans and in almost all other mammals, females carry two X chromosomes, designated XX, and males carry one X and one Y, designated XY.
   Section::::Single-gene.:Y-linked.
  
  Y-linked disorders are caused by mutations on the Y chromosome. These conditions may only be transmitted from the heterogametic sex (e.g. male humans) to offspring of the same sex. More simply, this means that Y-linked disorders in humans can only be passed from men to their sons; females can never be affected because they do not possess Y-allosomes.
  
  Y-linked disorders are exceedingly rare but the most well-known examples typically cause infertility. Reproduction in such conditions is only possible through the circumvention of infertility by medical intervention.
  
  Section::::Single-gene.:Mitochondrial.
   To focus more on the offspring and how it results in the formation of the f1 generation, is an inheritance called sex-linkage, which is a gene which is located on the sex chromosome and patterns of these inheritance differ in both male and female. The explanation that proves the theory of the offspring having genes from both parent generations, is proven through a process called crossing-over, which consists of taking genes from the male chromosomes and genes from the female chromosome, resulting in a process of meiosis occurring, and leading to the splitting of the chromosomes evenly. Depending on which genes are dominantly expressed in the gene will result in the sex of the offspring. The female will always give an X chromosome, whereas the male, depending on the situation, will either give an X chromosome or a Y chromosome. If a male offspring is produced, the gene will consist of an X and a Y chromosome. If two X chromosomes are expressed and produced, it produces a female offspring.
   Plants with sex-determining chromosomes, like "Silene," can develop uni-sexual reproductive structures because of the loss and gain of sex-determining genes. Mutations can cause female sterility, male sterility, or adverse combinations of genes that can lead to monoecy, gynodioecy, and dioecy.
  
  Section::::Species of "Silene" with different Reproductive Systems.
   Like most other male mammals, a man's genome typically inherits an X chromosome from his mother and a Y chromosome from his father. The male fetus produces larger amounts of androgens and smaller amounts of estrogens than a female fetus. This difference in the relative amounts of these sex steroids is largely responsible for the physiological differences that distinguish men from women.
   In female humans, Barr bodies are defined as the condensed and inactivated X-chromosome that is found in every cell of the adult. Because females have two nearly identical X chromosomes, one of them must be silenced so that the expression levels of the genes on the X-chromosome are of the proper dosage. Thus, males and females have the same level of X-chromosome expression, despite being born with one X for males and two for females. This is also why individuals with Klinefelter syndrome, a disease in which more than two sex chromosomes are present in the body, have fewer symptoms than individuals with other types of aneuploidy, which are often fatal before birth.
   Since humans have several times as many genes on the female X chromosome than on the male Y chromosome, X-linked traits are much more common than Y-linked traits. Additionally, there are more X-linked recessive conditions than X-linked dominant, and X-linked recessive conditions affect males much more commonly, due to males only having the one X chromosome required for the condition to present.
   Humans, as well as some other organisms, can have a rare chromosomal arrangement that is contrary to their phenotypic sex; for example, XX males or XY gonadal dysgenesis (see androgen insensitivity syndrome). Additionally, an abnormal number of sex chromosomes (aneuploidy) may be present, such as Turner's syndrome, in which a single X chromosome is present, and Klinefelter's syndrome, in which two X chromosomes and a Y chromosome are present, XYY syndrome and XXYY syndrome. Other less common chromosomal arrangements include: triple X syndrome, 48, XXXX, and 49, XXXXX.
  
  Section::::Mechanisms.:Other animals.
   BULLET::::- Hemophilia refers to a group of bleeding disorders in which it takes a long time for the blood to clot. This is referred to as X-Linked recessive. Hemophilia is much more common in males than females because males are hemizygous. They only have one copy of the gene in question and therefore express the trait when they inherit one mutant allele. In contrast, a female must inherit two mutant alleles, a less frequent event since the mutant allele is rare in the population. X-linked traits are maternally inherited from carrier mothers or from an affected father. Each son born to a carrier mother has a 50% probability of inheriting the X-chromosome carrying the mutant allele.
   Out of 300,000 species of angiosperm, "Silene" are among the 5 to 10 percent whose individual offspring can be of different sexes. Hetermorphic sex-determining chromosomes are very infrequent in plant genera; some notable examples that possess them, other than "Silene", are "Rumex, Humulus, and Cannabis".
   Many groups of organisms in addition to therian mammals have Y chromosomes, but these Y chromosomes do not share common ancestry with therian Y chromosomes. Such groups include monotremes, "Drosophila", some other insects, some fish, some reptiles, and some plants. In "Drosophila melanogaster", the Y chromosome does not trigger male development. Instead, sex is determined by the number of X chromosomes. The "D. melanogaster" Y chromosome does contain genes necessary for male fertility. So XXY "D. melanogaster" are female, and "D. melanogaster" with a single X (X0), are male but sterile. There are some species of Drosophila in which X0 males are both viable and fertile.
   All diploid organisms with allosome-determined sex get half of their allosomes from each of their parents. In mammals, females are XX, they can pass along either of their X’s, and since the males are XY they can pass along either an X or a Y. For a mammal to be chromosomally female, the individual must receive an X chromosome from both parents, whereas to be chromosomally male, the individual must receive a X chromosome from their mother and a Y chromosome from their father. It is thus the male’s sperm that determines the sex of each offspring in humans.
   Females possessing one X-linked recessive mutation are considered carriers and will generally not manifest clinical symptoms of the disorder, although differences in X chromosome inactivation can lead to varying degrees of clinical expression in carrier females since some cells will express one X allele and some will express the other. All males possessing an X-linked recessive mutation will be affected, since males have only a single X chromosome and therefore have only one copy of X-linked genes. All offspring of a carrier female have a 50% chance of inheriting the mutation if the father does not carry the recessive allele. All female children of an affected father will be carriers (assuming the mother is not affected or a carrier), as daughters possess their father's X chromosome. If the mother is not a carrier, no male children of an affected father will be affected, as males only inherit their father's Y chromosome.
   The arrangement of OPN1LW and OPN1MW, as well as the high similarity of the two genes, allows for frequent recombination between the two. Unequal recombination between female X chromosomes during meiosis is the main cause of the varying number of OPN1LW genes and OPN1MW genes among individuals, as well as being the cause of inherited colour vision deficiencies. Recombination events usually begin with misalignment of an OPN1LW gene with an OPN1MW gene and are followed by a certain type of crossover, which can result in many different gene abnormalities. Crossover in regions between OPN1LW and OPN1MW genes can produce chromosome products with extra OPN1LW or OPN1MW genes on one chromosome and reduced OPN1LW or OPN1MW genes on the other chromosome. If crossover occurs within the misaligned genes of OPN1LW and OPN1MW, then a new array will be produced on each chromosome consisting of only partial pieces of the two genes. This would create colour vision deficiencies if either chromosome were passed onto a male offspring.
   Most mammals, including humans, are genetically determined as such by the XY sex-determination system where males have an XY (as opposed to XX) sex chromosome. It is also possible in a variety of species, including humans, to be XXY or have other intersex/hermaphroditic qualities, though one would still be considered genotypically (if not necessarily phenotypically) male so long as one has a Y-chromosome. During reproduction, a male can give either an X sperm or a Y sperm, while a female can only give an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce a female.
   X-linked recessive conditions are also caused by mutations in genes on the X chromosome. Males are more frequently affected than females, and the chance of passing on the disorder differs between men and women. The sons of a man with an X-linked recessive disorder will not be affected, and his daughters will carry one copy of the mutated gene. A woman who is a carrier of an X-linked recessive disorder (XX) has a 50% chance of having sons who are affected and a 50% chance of having daughters who carry one copy of the mutated gene and are therefore carriers. X-linked recessive conditions include the serious diseases hemophilia A, Duchenne muscular dystrophy, and Lesch-Nyhan syndrome, as well as common and less serious conditions such as male pattern baldness and red-green color blindness. X-linked recessive conditions can sometimes manifest in females due to skewed X-inactivation or monosomy X (Turner syndrome).
   Genes which are specific to the X or Y chromosome are called sex-linked genes. For example, the genes which create red and green retinal photoreceptors are located on the X chromosome, which men only have one of. Thus red-green color blindness is an X-linked recessive trait and is much more common in men. However, sex-limited genes on any chromosome can be expressed to indicate, for example, "if in a male body, do X; otherwise, do not."
   Duplication of genetic material on the X chromosome in the region that contains the NR0B1 gene can cause a condition called dosage-sensitive sex reversal. The extra copy of the NR0B1 gene prevents the formation of male reproductive tissues. People who have this duplication usually appear to be female, but are genetically male with both an X and a Y chromosome.
  