Added: Genea Wold - Date: 20.07.2021 09:36 - Views: 10292 - Clicks: 1040
Not intercourse, though — more about how genetic sex is programmed during development. Sexual identity has been in the news often lately, and unsurprisingly so: the past few years have yielded sweeping reforms in civil rights, spurring new conflicts surrounding everything from age-old battles in gender equality to legislation enforcing anti-transgender bathrooms.
Most multicellular organisms, humans included, use sexual reproduction to reproduce. Compared to asexual reproduction, in which cells can simply create carbon copies of themselves, sexual reproduction allows for the introduction of genetic diversity into a population. In most sexually reproducing organisms, there are two sexes — but the ways in which these sexes are determined and the ways in which they manifest vary greatly. What are the ways in which sexual characteristics are encoded? Why are there so many systems for one seemingly common result?
We were all taught the classic recipe in grade school: an X chromosome from mom and an X chromosome from dad will yield a genetic female, while an X chromosome from mom and a Y chromosome from dad will yield a genetic male. Briefly, human cells all carry chromosomes, which carry our genes.
When egg meets sperm, each parent contributes 22 non-sex chromosomes and one sex chromosome — always an X from the mother, and either an X or Y from the father. Thus, the contribution from the father determines the sex of the baby . Following fertilization, a fetus begins to develop. At first, its sexual organs manifest as a genderless gonador sex gland — basically a small, thick ridge of tissue near what will become the abdomen.
SRY is a transcription factor — a genetic element that can turn on the expression of other genes. Unsurprisingly, with the immense variation observed in our natural world, more than one sex determination system exists. Ours, XY, is not even predominant. A few key examples tend to predominate: the ZW system in birds, XO in insects, haplodiploidy, and environmental sex determination systems.
After this, things start to get a little weirder. Honeybees utilize the system of haplodiploidy Figure 1Din which unfertilized eggs which carry only one set of chromosomes and are thus haploid develop into males and fertilized eggs which carry two sets of chromosomes and are thus diploid develop into females. Importantly, this is distinct from the XO system, where progeny inherit two copies of all non-sex chromosomes, regardless of sex; in haplodiploidy, males inherit only one copy of all chromosomes, sex and non-sex Figure 2A.
Honeybee colonies typically center around a single fertile queen, serviced by an army of male drones and female workers. The queen lays a vast of eggs, some of which are fertilized and develop into females.
Those that remain unfertilized develop into males. Thus, in this system, males have no fathers and can produce no sons. Thus, the community structure revolves around the queen. This is an interesting case where the genetically determined sex of individuals shapes their role within the larger community. However, this rule does not hold true in every species — sometimes the opposite rule is in effect, or temperatures at either extreme produce one sex, while an intermediate temperature produces the other.
Some snails and fish are actually able to reverse sex midway through life, depending on environmental conditions, in a process called sex reversal. Thus, genetic sex is a far more fluid process than one might assume. The fact that genetic sex can be directed by the flip of a single switch may be surprising. Sex is complex — but then again, there are a lot of other factors at play and, clearly, environment can have a big influence on how sex expresses itself.
For instance, we know of genetically XX persons who have developed testes and external characteristics of men, and genetic XYs who develop as females. An example of the latter case occurs in Swyer Syndrome, often when there is a mutation in the SRY gene.
Swyer Syndrome patients develop externally as female, but do not have ovaries and are infertile. Finally, inheriting extra or too few chromosomes can considerably alter how sex manifests. Klinefelter is a common example, as well as Turner Syndrome XOwhere a sex chromosome is missing, often leading to developmental defects.
Thus, all it takes is a small genetic change to turn SRY, or any of the genes it targets, on or off. We know very little about how sexual reproduction and sex determination systems evolved — the theories are, of course, difficult to test. But another important question is, once sexual reproduction did evolve, why did it branch off in so many ways?
And, perhaps more pressingly, is it still evolving in ways that could affect us? The answers are still mostly elusive. There has been some indication that the XY and ZW systems are still connected to a common ancestor, even though they manifested a complete reversal somewhere down the line. Interestingly, though, the platypus Y lacks SRY. In its current state, the Y chromosome is much smaller than the X chromosome, and appears to have lost the unnecessary X genes  along the way. Y continues to exhibit s of this very, very slow Y degeneration as time progresses.
In fact, the XO sex determination system is believed to have arisen from complete loss of an effective Y chromosome that was ultimately discarded for its relative inefficiency. Complete loss of Y is a pretty extreme event, and much evidence has accumulated that the loss of genes from the Y chromosome will ultimately plateau. Sex determination in humans is fairly well established. A final lesson comes in with the fairly new discovery of polygenic sex determination PSDwherein multiple genes and chromosomes contribute to the ultimate sex of offspring. This can take the form of XY and ZW systems being combined into the same species, for instance.
Domesticated cantaloupes yes, the fruit produce four sexes, and there is some evidence that several species of fish rely on PSD. This system is still poorly understood, but importantly, the added variation on each side of the equation indicates that even genetic sex is often not a binary trait. Not that he could have known at the time — no one did.
So, moot point. In fact, in women, who have two X chromosomes, one X chromosome in each cell is packaged into a dormant state called a Barr body. Cool fact: if you stumble upon a male calico cat, it is almost certainly XXY. Featured image from Wikimedia Commons. Chromosomes determine if you are male or female, not your state of mind. Not surgery, and not hormones. We live and love and learn and contribute and age like everyone else.
How about trying to think of us as just not chromsomally like you happen to be? Ha here we go. Besides your Whatever u want vgl white male wants to please fundamentalist ideas and bigotry. What other reason have you got to reject these ideas? I am an XY female. Wake up world! Humans are not chromosomally nor genetically binary! On strictly medical terms. As a surgeon, i apologize if i seem slightly absorbed, but i have to take a firm stance on this topic.
I see the point here, if you have a little girl. Both seem pretty understandable.
Looking at the first and third comentors it would appear they are experiencing the back fire effect. Not really helpful or insightful.
The point was to get people thinking about gender and how we as humans perceive it. It was also not mentioned that same sex rape happens. Both the article and the surgeon miss 2 conditions that make the gender based on DNA not so simple. So XX is a girl and XY is a boy. Neat, easy, no thought. Not so neat and simple right. Is check their pants they say. Ah that can be a problem too. Many who have XXY do not hconditionnizable genitals. So what to do?
B the second condition chimerism is when one person hold DNA of more than one more individual. So that hand may not be XX like the rest of you. The real reason this is all being discussed is that gender matters to society. If male amd female were true equals then it would not matter if you were male, female, or inbetween. We have constructed roles and expectations based upon our perceived gender. It IS about human beings. If you have never been discriminated against because of the way you look or act you will never unstand what it is like.
Treating people a certain way just because of their genetics is not a good idea, just ask a Jew. What is not understood is feared; what is feared becomes hated. Thus what we hate we destroy. I could not stop laughing while reading your reply Lauren. As the facts stand this is all there is XX and XY. Everything else is physical or mentally retardation, or people in serious need of professional counselling. Which is less than.
Which sums everything both of you have said. Nice and tidy. Truth is if gender was fluid, then so is race, which then means both are only a state of mind. Which in that case I identify as a polka dotted apache helicopter, and you should respect that. Then I should also be able to say I identify as a woman to be able to apply for and get a small business administration loan for Women-owned businesses, from the government which is specifically an advantage only for women.
From the SBA. Funny part is that will never happen because people only want equal rights as long as it is in their favor. Fun world we live in. You just said all non-binary individuals have mental retardation.
I hope you share your opinion with everyone you can.Whatever u want vgl white male wants to please
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