I’m sure you’ve all read it. Someone saying, well, you have male chromosomes so you’re a man and that’s it, or vice versus, that you’re a woman and that’s it. Biology isn’t that simple or that cooperative. Androgen receptors are not always coded properly because there are genetic variances in the DNA.
DNA isn’t a literal blueprint, the expression of DNA depends on the environment the cells find themselves in. At least as I understand it, most of a person’s body isn’t really “male” or “female” beyond there being particular chromosomes in the nucleus. They matter in the gonads and they matter during fetal development.
Where the plan in the genes is called a genotype the expression that actually occurs is called a phenotype. If you ever look at two grown identical twins and see that they don’t look alike or that they have had different diseases or problems that is because they’ve had different environments.
There are a bunch of intersex conditions. Many of them start with “normal” chromosomes and some require a variant. I’ll put the sex chromosomes in parentheses before each case. The list is not a complete list. Just something you can bring up for the next person who claims chromosomes rule all.
(XY) Complete Androgen Insensitivity Syndrome (CAIS) is a rare disorder (1:20000 to 1:99000). CAIS girls have normal female external genitalia and usually have a shorter than normal vagina or may have no vagina. They are raised as girls and generally aren’t diagnosed until they fail to reach menarche. There have been a couple of cases as I understand of CAIS women actually carrying a child to term that was implanted into the woman rudimentary uterus.
(XY) Partial AIS (PAIS) is responsible for much of what people think of when they think of intersex or “hermaphrodite” people. Ambiguous genitalia ranging from having the urethal output of the penis not at the end in the glans but along the bottom, a small penis, a large clitorus, etc. Fortunately children born intersex are starting to be allowed to decide what to do after they grow up rather than having the matter decided at birth as has been done for years. Often this was done in the direction of changing the child to female, which was not always a good choice.
(XY) Swyer’s Syndrome missing gonads, the child appears female
(XXY) Klinefelter’s Syndrome
(XX) Mayer-Rokitansky-Kuster-Hauser syndrome is a situation (about 1:2000 live births) where the vagina and/or uterus is absent due to developmental issues in the womb.
(XYY) A rare chromosomal disorder, included here just to show the diversity of sex chromosome combinations
(Mosaic) People can be born with a genetic mix of sex chromosomes in their cells. It can literally be the case that someone can have some XX and some XY cells or some X cells. One possible reason is a pair of fraternal twins that merge early after fertilization.