Kasoro gani?
Mie ni mwanasayansi, sijasoma ungwini.
Nimesoma genetics, topiki inayofundishwa kwenye somo la Biology, form 4.
Topiki hii inafundisha juu ya:
1. Genetic orders of sexual development; na
2. Genetic Disorders of sexual development
Any idea?
Yaani:
1. JInsi mtu mwenye sumaku ya ashiku za kiume (androphilic orientation) na ashiki za kike (gynephilic orientation) anavyopatikana;
2. JInsi mtu mwenye sumaku ya ashiki zilizovurugika anavyopatikana.
Umewahi kujielimisha kuhusu haya?
Kama umesoma HGL na ungwini mwingine, bila shaka hapana.
Hivyo, tumia muda wako binafsi kujielimisha, ili kufuta ulofa wa kijenetiki (genetic illiteracy).
Hapa nakupa kwa muhtasari wa maarifa ya kijenetiki katika hatua mbili za:
1. Chimbuko wa wasifu wa kijinsia wa kawaida (hetero-affective sexual orientations):
2. Chimbuko wa wasifu wa kijinsia usio wa kawaida (homo-affective sexual orientations)
Vyanzo vya taarifa zangu ni vya lugha ya Kiingereza. Hivyo, naandika kwa Kiingereza, nitatafsiri baadaye.
Chimbuko wa wasifu wa kijinsia wa kawaida, wasifu wa mwanamume rijali na mwanamke rijali
The process of sex determination for the unborn child is governed by several genes within the first seven weeks of pregnancy.
This process goes through five main stages.
(a) Determination of the sex of the child at the cellular level (chromosome sex) during fertilization is explained in terms of the following steps.
(i) Through sexual intercourse, a male sperm with 23 chromosomes, including 22 chromosomes called "X" and one called "Y," unites with a female egg with 23 chromosomes called "X", creating a new compound cell having 46 chromosomes, which is called a zygote.
(ii) So, the result of the fertilization an egg by a sperm is a zygote capable of undergoing cell division to form a new individual.
(iii) Thus, this zygote can have either 46 chromosomes with a female format, that is, 'XX' (46XX Female), or 46 chromosomes with a male format, that is, XY (46XY Male).
(iv) In this first stage of sex determination, the pregnancy has a neutral reproductive system. Instead, there is a "tissue" having three parts: two bipotential gonads, two Mullerian ducts and two Wolfian ducts.
(v) Depending on the circumstances of the time, the bipotential gonads and their ducts can turn into male genitalia or female genitalia.
(vi) Thus, chromosomal sex answers the questions: Does the person have 44+XX chromosome structure that is typical of normal female persons? or Does the person have 44+XY chromosome structure that is typical of normal male persons?
(vii) A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(b) In the seventh week of pregnancy, witnesses the establishment of the sex of the child at the level of the gonad (gonadal sex). At this point, the two bipotential gonads, either will turn into female ovaries or will turn into male testicles.
(i) If the bipotential gonads turn into ovaries, the pregnancy of a female child is established. And if they turn into testicles, the pregnancy of a male child is established. These changes occur in the fifty-day-old pregnancy.
(ii) This stage is controlled by several genes, but the most important gene are the "sex determining region Y gene, that is “SRY gene." The "SRY gene" is a gene found at one end of the "Y" chromosome, which is the male chromosome.
(iii) The job of the "SRY gene" is to produce a chemical that turns the bipotential gonads into testicles. That chemical is a protein called called "testicle determining factor (TDF)."
(iv) The availability of SRY and TDF forces the two free gonads to turn into testicles, so that, a male pregnancy is achieved. This is an event in the seventh week of pregnancy.
(v) On the other hand, the absence of SRY and TDF allows the bipotential gonads to acquire the 'XX' genetic format, and hence to turn into ovaries, and thus, to facilitate a female pregnancy. This is an event in the seventh week of pregnancy.
(vi) Thus, if a child is born as a complete male, he has a genetic system having an "XY" format which is accompanied by the "existence" of "SRY gene." That is, he has a genetic structure having the format of “46XY Male, SRY+.”
(vii) On the other hand, if a child is born as a full female, she will have a genetic system having the format of "XX" being accompanied by the "lack" of an "SRY gene." That is, she will have a genetic makeup having the format “46XX Female, SRY-.”
(viii) So under stage two, two types of sex emerge. We have genetic sex and gonadal sex.
(ix) In short, genetic sex answers the questions: Does the person have genes that determine sexual development that is typical of normal male persons? or Does the person lack the genes that determine sexual development that is typical of normal female persons?
(x) And gonadal sex answers the questions: Does the person have two testicles that are typical of normal male persons? or Does the person have two ovaries that are typical of normal female persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(c) The third stage is the determination of sex at the genital level and several parts of the body, thus giving it a special morphology/appearance (genital sex).
(i) This stage is controlled by male hormones, such as testosterone, which is produced in the testes of the male fetus; and female hormones, such as estrogen, which is produced in the ovaries of the female fetus.
(ii) At this stage, the female fetus acquires the following external genitalia: the vulva, the vagina, the cervix and the urethra. In addition, a woman gets the following internal genitalia: the reproductive tract, uterus, two fallopian tubes and ovaries.
(iii) The male pregnancy, gets the following external genitalia: a penis and two testicles that descend into his pouch. In addition, the male pregnancy acquires the following internal genitalia: the prostate, the epididymis, the seminal vesicles, and the vas deferens.
(iv) Thus, at this stage, two types of sex emerge too. They are internal genetic sex and external genetic sex.
(v) Internal-genital sex answers the questions: Does the person have sperm transport system that is typical of normal male persons? or Does the person have the uterus, oviducts, and upper vagina that are typical of normal female persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(vi) And external-genital sex answers the questions: Does the person have a penis and scrotum that are typical of normal male persons? or Does the person have clitoris and vulva that are typical of normal female persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(d) The fourth stage is puberty sex differentiation, which is determined by the production of male and female sex hormones which starts after adolescence.
(i) These hormones have both physical and psychological effect to the growing person. So, we can talk about three types of sex so far, namely: hormonal sex, pubertal sex, and psychological sex.
(ii) Hormonal sex answers the questions: Does the person have hormones that are typical of normal male persons? or Does the person have hormones that are typical of normal female persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(iii) Pubertal sex answers the questions: Does the person have Adam’s apple, beards, pubic hair, body shape and skeletal growth that is typical of normal male persons? or Does the person have breast development, menstrual cycle system, and body shape typical of normal female persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(iv) And psychological sex answers the questions: Does the person have an androphilic sexual orientation that is typical of normal female persons? or Does the person have gynophilic sexual orientation that is typical of normal male persons?
A negative answer to both questions implies an "an irregular genetic situation" called a "Disorder of Sexual Development (DSD)."
(v) In summary, concerning the science of normal sexual differentiation, we have seen the following: That, the chromosomal sex of the embryo is established at fertilization.
This stage of embryonic development is sexually differentiated at a genetic level, but having sexually indifferent gonads. However, after six weeks of pregnancy further signs of sex differentiation are noticed.
This process of sex differentiation involves a series of events whereby the sexually indifferent gonads progressively acquire male or female characteristics.
The process of gonadal determination is governed by a complex network of genes, including the SRY gene, whose balanced expression levels either activate the testis pathway and simultaneously repress the ovarian pathway or vice versa.
Subsequently, internal and external genitalia will follow the male pathway in the presence of androgens and anti-MĂĽllerian hormone (AMH), or the female pathway in the absence of these hormones.
(e) As such, we can scientifically talk about eight categories of human sex, namely: chromosomal sex, genetic sex, gonadal sex, internal-genital sex, external-genital sex, pubertal sex, hormonal sex, and psychological sex.
(f) And, in conclusion, then, we can confidently say that, the normal sexual orientation of an individual person, whether androphilic or gynophilic, is congenital and not volitional, natural and not chosen.
(g) In the case of male pregnancy, it results from the presence of the following factors: SRY gene, a protein called TDF, anti-Mullerian hormone, and other factors.
(h) And in the case female pregnancy, it results from the absence of the following factors: SRY gene, a protein called TDF, anti-Mullerian hormone, and other factors. The fact of absence as a causal factor is explained above.
Chimbuko wa wasifu wa kijinsia wenye ulemavu, yaani wasifu wa mashoga, wasagaji na majike-dume
Is the existence of a condition of an abnormal sexual orientation scientifically supported? Our findings in response to this question are as follows, based on a sound theory of disorders of sex development (DSD):
(a) Just as there are persons with disabilities at a physical level having impaired parts of their bodies, such as squinting eyes, left-handedness, and other persons with disabilities(PWDs), there are PWDs at a sexual level too.
(b) For example, if a person has two genitals, namely, a "penis" and a "vagina," with one of them not functioning properly, then, that is a person with disability at a sexual level. This is a hermaphrodite.
(c) The science of abnormal sexual differentiation, refers to this abnormal phenomenon as a disorder of sexual development (DSD).
(d) According to the works of Vogel and Motulsky (2009) along with Crooks and Baur (2014) the origins of "Disorders of Sexual Development (DSD)," can be explained scientifically.
(e) Earlier we saw that, if a child is born as a normal male, he will have a genetic system having the format "46XY ME, SRY+." On the other hand, we said that, if a child is born as a normal female, she will have a genetic system having the format "46XX KE, SRY-."
(f) But unfortunately, if it happens that a pregnancy with a genetic system having the format "XY" is accompanied by a broken "Y" chromosome which has suffered a partial or total loss of an "SRY gene," then, serious genetic consequences will occur to the pregnancy, as discussed next.
(g) First, this pregnancy will not receive the Testicle Determining Factor (TDF), which is the "protein that triggers the growth of testicles," so that the child can be born male.
(h) Instead, despite the fact that the pregnancy has a male genetic format of 'XY,' at the chromosomal level, this pregnancy will develop ovaries as if the pregnancy had a female genetic format of 'XX,' which is the female genetic format, at the chromosomal level.
(i) Finally, a child will be born who is male at the cellular level, while he is female at the gonadal level. He will be a person with sexual disability at a sexual level, having a genetic format of "46XY Female, SRY-."
(j) Her ovaries will produce female hormones, and she will have a female morphology, while inside she has cells having a male format. She will be a genotypical male, who is a phenotypical female.
(k) This disorder of sexual development brings about a change which is called “male-to-female sex reversal.” So, this is how a man with a feminine appearance, like Caster Semenya, a South African athlete, comes into the world.
(l) Unfortunately again, if it happens that, a pregnancy with a genetic format of 'XX' is accompanied by an X chromosome that has picked up a "SRY gene," after it has accidentally broken off and dropped from the Y chromosome, serious consequences will befall the pregnancy too.
(m) First, this pregnancy gets "testicular growth protein," that is TDF, causing the child to be born with male genitalia.
(n) For this reason, despite the fact that the pregnancy has a genetic format of 'XX,' which is a female format, it will still produce testicles, as if the pregnancy had a genetic format of 'XY,' which is a male format .
(o) Finally, a child will be born with a female gender at the cellular level, while he has a male gender at the gonad level. He will be a genotypical female and a phenotypical male. He will be a person with disability at a sexual level having a genetic format of “46XX Male, SRY+.”
(p) His testicles will produce male hormones, and he will have a male morphology, while inside he has cells having a female format. This disorder of sexual development brings about a change which is called “female-to-male sex reversal.” This is how a woman with a masculine appearance can come into being.
(q) Again, if the "SRY gene” does not completely drop from the "Y" chromosome, then, male to female sex reversal, or female to male sex reversal, as the case may be, will be partial. As result, the pregnancy may have male genitalia and female genitalia.
(r) This is how hermaphrodites happen. In the modern terminology, they are otherwise called intersexed persons or simply intersexuals.
Hitimisho na mapendekezo
Napenda kuhitimisha uchambuzi huu kwa kusema mambo matatu:
Maarifa yote tuliyo nayo leo yanaongozwa na mifumo miwili ya maarifa.
Kwa upande mmoja kuna mfumo wa maarifa halisi (realism). Haya ni maarifa ambayo ukweli wake hautegemei maamuzi ya watu, hata kama wakitumia kanuni ya wengi wape.
Na kwa upande mwingine kuna mfumo wa maarifa yanayotokana na uhandisi wa kijamii (social constructionalism/fictionalism). Haya ni maarifa ya kikatuni. Usahihi au upotofu wake unategemea maamuzi ya watu kwa kutumia kanuni ya wengi wape.
UKweli kwamba mtu fulani anayo sumaku ya nyege inayomsukuma kwa mwanamke au kwa mwanamume hautokana na kura za wengi.
Kuna wanateolojia na wanazuoni baki hawataki kukubali ukweli huu. Lakini, wengi wao wamesoma ungwini. Wanasumbuliwa na ulofa wa kisayansi (scientific illiteracy), na hasa ulofa wa sayansi ya kijenetiki (genetic illiteracy).
Halafu wanafikiri kwamba wanaweza kutekeleza jukumu lao la kutakatifuza ulimwengu wa wanasayansi bila kujielimisha kwanza kuhusu misingi ya sayansi ya kijenetiki. Hawawezi kamwe.
Giza haliwezi kusinda mwanga wa ukweli.
Naishia hapa kwa sasa.
Karibu.
