After the discovery of the testis-determining gene SRY , many scientists shifted to the theory that the genetic mechanism that causes a fetus to develop into a male form was initiated by the SRY gene, which was thought to be responsible for the production of testosterone and its overall effects on body and brain development. This apparently happens with some regularity, and whenever sexing snakes, especially pythons, we have found it strongly advisable to probe both sides of the cloaca. In some sandboas and in rosy boas, the spurs of males are small but visible, while females have no visible spurs. Once viewed simply as an impediment to fertilization , recent research indicates the zona pellucida may instead function as a sophisticated biological security system that chemically controls the entry of the sperm into the egg and protects the fertilized egg from additional sperm. In most cases, the size and shape of spurs are an indicator of the sex of a boa or python, but this is not always an accurate means to determine sex with certainty. The presence of Y chromosome genes is required for normal male development. The probe passes inside the inverted hemipenis of a male snake. Deficiencies occur more commonly in pregnancy because of the increased nutritional needs of the baby.
In general, however, differences in tail length are not a satisfactory means of determining sex. The increased internal pressure in the base of the tail generated by the pressure of the thumb causes the hemipenes of the males to pop out. A spur typically consists of a spur base which is capped with a spur claw; species with spurs have one spur at each side of the anal scale. Were comparison possible, the everted hemipenes of male blood pythons are bigger, with more structure and more vascularization than the relatively smooth, pale, everted hemipenial homologs of females. Reviewed by Mary D. Aside from timing it right and praying , you can do little to influence gender during conception. The measure of the penetration of the probe into the base of the tail is the number of subcaudal scales spanned by that distance, counted from the vent posterior to the scale at the level of the maximum penetration of the probe. Cravings for ice or laundry starch suggest an iron deficiency, and cravings for chalk or dirt may indicate the need for more essential fatty acids. But this work shows that the activity of a single gene, FOXL2, is all that prevents adult ovary cells turning into cells found in testes. The use of an appropriate-diameter clear-plastic tube is a very safe and appropriate means to restrain delicate snakes, biting snakes, and venomous snakes. In general, female hemipenial homologs do not evert, as do male hemipenes. In an interview  for the TimesOnline edition, study co-author Robin Lovell-Badge explained the significance of the discovery: Sometimes keepers will choose to use a probe that is too narrow on the incorrect assumption that this will make probing the snake easier. If a woman craves sour, salty, spicy or protein-rich foods, some people claim that she must be having a boy. Determining the Sex of Snakes Dave and Tracy Barker The Sex Determination of Snakes It's hard to image today that only a few decades ago, most keepers had no idea what was the gender of the snakes they kept. However, most snakes do not have physical characteristics that will visually identify their sex. These paired funnel-shaped structures become increasingly narrow, ending in connective ligaments that continue toward the tip of the tail to insert on posterior subcaudal vertebrae, as do hemipenis retractor muscles. As pictured here, the probe is inserted into the cloaca and directed against the posterior wall of the cloaca to determine if it can be passed into the tail, and if so, how far. One mistake made by many keepers is to use a probe that is too small in diameter. Sexually dimorphic characters Throughout the snake kingdom, most species show only minor, if any, external difference between the sexes. Simple blood tests can determine whether you have any nutritional deficiencies. When a probe is inserted into the tail of a male snake, it is actually being inserted into a space surrounded by the external surface of the hemipenis. Of course, if no combat is observed, they could be a male and female or both females. This apparently happens with some regularity, and whenever sexing snakes, especially pythons, we have found it strongly advisable to probe both sides of the cloaca. Usually this does not affect the outcome, but in some cases and some species, the determination made by a small probe is uncertain, as a small probe may pass relatively deep into the hemipenial homologs of a female. During pregnancy, women might crave specific foods, consciously or unconsciously, as a response to emotional needs.
Video about determining the sex of the baby:
Sex Determination: More Complicated Than You Thought
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