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is it true that all fetuses start out in a female form?
- Anonymous1 decade agoFavorite Answer
Yes all fetuses start out is female, though they are already male or female at the DNA level. Actually all fetuses start out as tadpoles more or less. The changes occur if the fetus creates certain male hormones, which sometimes doesn't happen in a baby that is male DNA wise, and sometimes does happen in a fetus that is female DNA wise.
The cells that become the clitoris in a girl, become a penis in the boy. The clitoral hood and foreskin are the same in the begining. The ovaries become the testes, and the labia the scrotum.
"Initially, all human fetuses are female, in that the default pathway is to develop into a female. During the eighth week of gestation, the presence of a Y chromosome and a functional locus for the SRY gene product, also called the testes determining factor (TDF), determines if testicular development will occur. This process converts the inherently female fetus into a male one, as a steadily increasing surge of testosterone is then produced by the testes. Much of the testosterone is converted to dihydrotestosterone, which is the key hormone to virilize the fetus. Along the biochemical pathway, other recently identified gene products likely play an additional role in the masculinization of the fetus.
Further progression toward the eventual male phenotype occurs as antimüllerian hormone is produced, inhibiting the formation of müllerian ducts, which would lead to female genital development. The fetal brain is also affected by this process. The corpus callosum, amygdala, cerebellum, and portions of the preoptic area of the hypothalamus are larger in brains exposed to testosterone. Corresponding parts of the brain are smaller in female, or testosterone-deprived, fetuses. Indeed, in the absence of testosterone, the fetus continues its progression in the female state. Development of the ovaries and the female genital tract is likely triggered by follicle-stimulating hormone (FSH), which is present in both male and female fetuses, but whose effect is masked by the testosterone surge in males.
The gender identity of a fetus, and later an infant, is still incomplete. Yet, current research indicates that because of the expected hormonal exposure secondary to genetic sex, a certain gender bias probably exists in all newborns. This rudimentary gender identity, although incomplete, is an important determinant in gender development. The dimorphism of the brain itself suggests this. Nevertheless, variations may occur when endogenous or exogenous factors create a fetal environment where hormone levels do not follow the genetically determined pattern. The gender bias of these infants may be tilted away from one that correlates with the genotype. Such variations are discussed below. "
"8th WEEK: Major organs begin development.
Now about size of hen's egg.
Embryo is 1" long and about 4 grams.
Hands and feet are seen.
Baby is extremely reactive to its environment.
Male sex hormone (testosterone) produced by testes
Masculine development in males - no change in females."
"When the genitals begin to form
Male and female genital systems are identical through the sixth week of gestation or the eighth week of your pregnancy. By week 12 to 14, your baby's external genitalia are recognizably male or female, but they're still not completely formed. On ultrasound, if your baby is cooperating and is positioned in a favorable way, his or her sex can be identified as early as the 16th to 18th week of your pregnancy. Of course, if your baby is "hiding his stuff" (positioned in such a way as to prevent identification), it will make no difference how far along in your pregnancy you are--you won't find out your baby's sex"
Sorry that's the best I can find in the time I am willing to spend doing your research for you.
- Anonymous6 years ago
Best answer is not correct. Dumbing this down is the reason for the misconception.
"Actually all fetuses start out as tadpoles more or less."
No they start at fertilization and then progress to eventually be tadpole like.
The clitoral hood and foreskin are NOT the same in the "beginning", they are undiferetated and are therfore not yet a clitorsal hood or foreskin.
"The ovaries become the testes, "
No,the gonads are never at any point ovaries in a male fetus. They begin undifferentiated which means neither ovaries or testes. Notice the parts that reads, " yet-undifferentiated gonad, turning it into a testis"
"TDF is a member of the SOX (SRY-like box) gene family of DNA-binding proteins. When complexed with the SF1 protein, TDF acts as a transcription factor that can upregulate other transcription factors, most importantly SOX9. Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. These cords form in the central part of the yet-undifferentiated gonad, turning it into a testis."
"This process converts the inherently female fetus into a male one"
This is inaccurate, without the release of the proper hormones a male fetus will not turn out female, they will have the outward appearance of female but will have undescended gonads which will not function correctly and are often cancerous, they are removed as a precaution. People with AIS maybe exhibit this.
An undifferentiated fetus has a hole and not a pole and thus might appear more female but an undifferentiated fetus of any sex does not have female or male genitals.
- Anonymous5 years ago
Yes, it is. I really don't know why people think it's not. I am a transgender man, my gender was once female in the womb but became male due to exposure to a large amount of testosterone, that itself proves humans start out as female, otherwise I wouldn't have been born with a brain and body mismatch. Gender and sex are NOT the same. Gender is between your ears and sex is between your legs.
Sex is not permanent, adult humans can change sex if their genes are manipulated. The genes FoxL2 and Sox9 are present in males and females, but only one of them is activated at a time. If the gene that is activate is switched off, then the ovaries or testicles will cease to function correctly. Men and women both produce estrogen and testosterone, just in different amounts. If the Sox9 gene in a male body is switched off, the testicles will function like ovaries, and vice versa, if the FoxL2 gene in a female body is switched off, the ovarian tissue will become testicular tissue.
If my gender is male but my birth sex was female, then there is something fishy going on. Unless I started out as a female, then I must have a Y chromosome but for whatever reason didn't develop male genitals.
- **0_o**Lv 61 decade ago
all fetusus start out with undifferentiated sex organs. The actual sex of the baby is determined at conception, depending on whether the father adds an x or y chromosome. Its a burst of hormones released a bit later in development that "tell" the fetus to grow the appropriate parts if male. Intrestingly enough, sometimes, although VERY RARE, a fetus will have the xy genetic combination to be a male, but for some reason the development of the boy parts are never triggered. When that happens, the child is born genetically male, but physically female. wierd huh?Source(s): biology class
- oldhippypaulLv 61 decade ago
Yes the female is the default configuration for humans. Change to male comes later in development.Source(s): RN
- Anonymous1 decade ago
I believe that is true to a degree hence men having nipples. the sex is determined at moment of fertilisation due to man's chromosome (x or y). however, the genitalia doesn't actually develop until later in the pregnancy.
- 1 decade ago
The genitals start out looking like a nub. The nub either changes to the penis in the boy or the clitoris in the girl. The gender is determined at fertilization.
- Ms.DanielleLv 51 decade ago
- Katie CLv 61 decade ago
Sort of. The ovaries are developed first and sometimes they drop and turn into testicles or stay as ovaries.