#karyotype

[the-thinking-reed]

Lesson #1: Mitosis & Meiosis

I will be covering the phases of mitosis and meiosis, along with what chromosomes are, their karyotypes, and how DNA replicates.

Hello, students. Today is my first lesson to you all in rudimentary biology. Some of you may know that the first topic is about mitosis and meiosis, and to those who don’t: now you do. Knowledge is easy to impart, but it may be difficult to absorb for some. That is why I am providing lessons to the masses with this method, so that I can bolster those that are eager to learn.

As stated in the lesson brief, by the end of this lesson, you will have learned about the process of cell division for somatic cells and sex cells. You will also have learned about chromosomes, the charts they are organized in called karyotypes, and how DNA is replicated.

Because of this, I want to disclaim that the discussion of chromosomes and sex cells means that I will use terms regarding a person’s sex, but I will not use terms regarding a person’s gender. It is imperative that sex and gender are not the same thing is said. Gender is a social construct, meaning that it is not rooted in biology, it is just how we think of ourselves. Sex is rooted in biology, but it is still not binary itself. Cases like individuals being intersex for example is not something I will explicate in this lesson. If it is something you all would like a lesson on, please feel free to suggest so. I just need you all to know that human biology is versatile. Not everything will work out the same way, and that is the truth.

Let us begin.

Mitosis is the division of somatic (body) cells. Body cells are blood cells, muscle cells, and nerve cells, for example. The process is quick, thus meaning that cells do not spend much of their lifespan dividing. What they spend most of their time in is interphase.

Interphase has several stages — three to be exact. G1, S, and G2 are the three steps in interphase.

G1, also known as the growth 1 phase or the gap 1 phase, is the first stage the cell will go through as it matures. The cell is quite active during this stage, as it is growing. It takes DNA and proteins to serve as “building blocks”, so that it can create chromosomes later.

S, also known as the synthesis phase, is the second stage the cell will go through. The DNA within the nucleus replicates itself. This is because when the cell is about to divide, its offspring will be ensured to have a copy of the original cell’s DNA, which will allow the product of mitosis to be genetically identical to its parent. This process takes the longest in interphase, simply because the genetic material being replicated is complex.

I would like to briefly detour to explain how exactly DNA replicates itself. Such a process begins when either side of the structure pulls apart at a designated region labeled the origin of replication. Each side is left open, and the bases of each side have no other base to complement them. Bases in DNA are always paired with another base, and the base another base will be connected to always stays the same depending on the kind of base. So, loose nucleotides, which are the building blocks of DNA, will come to the opened sides and the bases in those nucleotides will pair up with the bases on either half of DNA. This will result in two new strands of DNA which will twist back to form the look of DNA most are familiar with. Because of the process, newly made DNA is semiconservative, meaning that half of the DNA is consisting of the original strand, and the other half is a newly made strand.

Let us return to the current topic. The last stage in interphase is G2, also known as the growth 2 phase or the gap 2 phase. The cell does not spend as much time in this stage of interphase in comparison to the other two stages. All the cell does is replenish the energy lost from the previous stage and engage in additional growth.

Interphase must be completed before the cell divides, as this phase is what prepares the cell for mitosis.

Now we may move onto mitosis.

Cells may divide for several reasons, some being for growth of the organism, to repair damage somewhere in the body, or to replace old cells because cells die constantly. There are five stages of mitosis: prophase, metaphase, anaphase, telophase, and cytokinesis.

Before we go further, I must explain chromosomes. In short, chromosomes are rod-like structures that consist of DNA, which is called chromatin in this situation, and protein. Chromosomes are made of two sister chromatids, which are held together in the middle by a centromere. Chromosomes come in pairs, and within a human somatic cell, there should be 46 chromosomes in total. Within a human sex cell, there should be 23 in total. Having two pairs of chromosomes, meaning that there are 46 chromosomes in total, means that the cell is diploid. Having one pair, resulting in only 23 chromosomes, means that the cell is haploid. Somatic cells are diploid, and sex cells are haploid.

Prophase is the first phase. The prefix “pro-“ means before. The chromatin and proteins in the nucleus form chromosomes. Meanwhile, the membrane of the nucleus dissolves and the centrioles on either side of the cell form thin structures called spindle fibers.

After prophase is metaphase, the second phase in mitosis. The prefix “meta-“ means between in this case. The nucleus is now gone, and the newly made chromosomes line up in the middle of the cell. The spindle fibers attach to each sister chromatid on both sides of the cell.

What follows after is anaphase, the third phase. The prefix “ana-“ means away in this case. The chromatids are separated from each other by the spindle fibers.

Telophase is the fourth phase of mitosis. The prefix “telo-“ means end. The spindle fibers dissolve, and the chromosomes are kept separated in newly formed nuclei. The cell begins to divide. The dip between two cells dividing is called the cleavage furrow.

We have made it to the final phase of mitosis — cytokinesis. The cells fully separate and are two individual beings that are genetically the same from originally having the same chromosomes.

As for the other type of cell division, meiosis can only create sex cells, or gametes. The sperm and the egg are gametes. Now, this process directly correlates to chromosomes, so pay attention. The process is twice as long as mitosis, but what exactly happens within these phases is virtually the same.

Karyotypes are a chart of an individual’s chromosomes. Like explained earlier, gametes will have 23 chromosomes, with each chromosome in 23 spots. The 23rd spot in the karyotype in both somatic cells and gametes will contain X or Y cells. Because somatic cells are diploid, if an individual has a combination of XX or XY chromosomes occupying that 23rd spot, the reproductive system of the organism is determined. As for gametes, because they are haploid, depending on the kind of gamete, the 23rd spot will only contain either an X chromosome or a Y chromosome. Eggs, which are produced by the female reproductive system, can only contain the X chromosome. Sperm, which are produced by the male reproductive system, can contain either an X chromosome or a Y chromosome.

Remember: somatic cells determine the sex of the individual, and gametes help create that combination of X and Y.

During sexual reproduction, when the sperm meets with the egg, the sperm will bring either X or Y to the X of the egg, thus determining to sex of the offspring. An XX combination will typically result in female reproductive parts for the offspring, and XY will result in male reproductive parts. This however, is not always the case, and sometimes the offspring will have differing karyotypes than a traditional two chromosomes at the 23rd spot. These cases are rare, but they do happen because the chromosomes may fail to separate during meiosis, which is called nondisjunction.

As for the actual process of creating the sperm and the egg, it starts with the first phase labeled prophase I. The chromosomes are created. In metaphase I, the chromosomes line up in the middle of the cell, and the spindle fibers formed previously in prophase I pull the sister chromatids apart in anaphase I. Then in telophase I and cytokinesis, the cell divides. This process will repeat with the two cells until there are now four cells. This part has each phase labeled the same, but it is prophase II all the way to telophase II.

It is important to note that the cells in meiosis begin as diploid, but since genetic information is pulled apart more than once, the four offspring of meiosis are haploid.

There are also important events that are unique to meiosis, which result in the offspring being genetically different rather than identical like in mitosis. The first is crossing over. This occurs in prophase I when the chromosomes will exchange DNA. The second is independent assortment, which occurs in metaphase I. This is when the chromosomes line up in the middle randomly. Because of these phenomenons, the products of meiosis are genetically unique.

That concludes my first lesson to you all. I hope you were paying attention — if not, then leave. I would like to note that if there is a topic you would like me to cover in a future lesson, my asks are open. I would like to apologize if my lesson seems as if I’m droning on, and the paragraphs of text do not provide a clear picture for some of you. I had intended to put illustrations throughout the lesson, but unfortunately Tumblr will not allow me to.

That being said, you can only learn if you are truly willing to. Let logic disseminate.

[thisis-intersexism]

sorry if this is weird to ask but how do you get karotyping done / how does karotyping work ? i didn't learn in biology and i wanna know more

I'm not 100% sure, anon! I haven't done much research on that yet, any help from the community would be greatly appreciated!!

[machine-unlearning]

[transitorri]

It's a Box With Nothing In It

Seeing the Supreme Court hearings today, really more of a job interview, for our next potential Justice of the United States Judge Jackson was asked her definition of what a “Woman” is, she refused to give an answer. Later John Roberts asked Marsha Blackburn for her definition, her response “I would say I am a woman. I am a Female, Females are women” I hope I don’t need to point out how very poor of a definition this is. But, the core of this question is actually something as a trans individual you have to grapple with, because a lot of soul searching is needed to answer it. So, here’s my experience, trying to answer that question directly.

Without going deep into the weeds on biology and that useless debate of “Well women have XX chromosomes and Men have XY and that’s biology and there’s nothing more to it.” Let us instead get even more basic, really basic. In order for a “thing” to be classified as a “thing” it has inherent in it a certain set of characteristics that we decide make it one “thing” or another “thing. Birds have feathers, plants require photosynthesis, dogs and cats are mammals and different shapes. Pretty basic stuff.

Think of this sorting as a “box” outside we label the thing “Trees” and we list the needed properties that make a “Tree” a “Tree”, leaves, bark, photosynthesis. In order for a Thing now to be a Tree and go in the “Tree Box”, it must have these properties. With this criteria in mind, let’s come back again to our idea of “Woman”, we could use ‘man’ as well, but I’m a trans woman and more people seem eager to discuss us instead of transmen who often get overlooked entirely, so let’s go with it.

Let’s make a list, I tried making one since that’s important to me as I transition to try and answer these questions. What do we define as “Woman '' well, they paint their nails, have long hair, cry more often, wear dresses and skirts, sit down to pee, birth children, have different genitals, have breasts, XX/XY chromosomes etc.

Now, let’s really go through that list. Do all women paint their nails or is it possible to be a woman and not do that? Yes, you can be a woman and not paint your nails. Wearing dresses? Having long hair? Ok, let’s skip the obvious. Birthing babies? Is it a requirement that to be called a “Woman” you must be able to bear children or do women exist who are unable to do this? I think sterile women are still defined as being women. Going down this list we can eliminate anything social, cultural and many things physical as well such as having bright voices, being physically small or even weaker than men.

Eventually, we end up having to deal with the only line in the sand left that is defensible for the definition, genitalia and chromosome pairings, but, we as a society do not examine one’s genitals to know how we’re going to interact with someone. We as humans do not go around like dogs sniffing each other's genitalia to make such a determination about what and who they are. Similarly, if a man goes to war and is injured in a way where his genitals must be amputated, is he still a man or not? Do genitals then determine if someone is ‘man’ or ‘woman’ then? Or is that another property we strip off the box because it no longer serves as a defining property?

Likewise, most people have never had themselves tested for their chromosomal pairings, it’s not a test we conduct on every infant born to determine what gender path to set them on through life. Nor do we ask to see such a test before we make a judgment about whether we call them “Mam” or “Sir”, both of which may not be labels the person identifies with at all. Most people do not even know what their exact karyotype even is, and I suspect many would be surprised to discover they're not what they thought they were. Finally the concept, the very idea of “man” and “woman” existed long before the understanding or chromosome were discovered and understood by more modern science.

With all of that said, we end up with a box that has a list of characteristics, any one of which could be stripped away until there’s nothing left at all. Does this mean the box itself doesn’t exist? Does the word “woman” mean literally nothing? Well, yes and no. The box exists but it's one with nothing in it. A concept with a loose definition of traits that are a mix of biological, cultural and social, no one ‘thing’ or even smaller collection of things defines the word. At best, a collective grouping of such traits might define someone as a “man” or “woman” but those by themselves don’t define the word, they’re an approximation of if we address someone as “Mam” or “Sir”. It’s a guess at best unless the other person lets us know certain information.

To parrot a phrase you’ve probably heard before on the topic, “Gender is a social construct”. Society and culture define what is or is not a “woman” and that encompasses behavior, fashion of dress, and most other properties. These elements are far more closely linked to what we view as a “woman” or not than our biology. That is how I loosely define “Woman” because the word itself cannot be tightly defined the way we do ‘Tree’ or ‘Bird’ unless we remove everything that makes us human at all.

[ephemeriee]

[moleculart]

embroidery: the telomeric effect

A karyotype, in this case it is that of a female’s, with the ends of the chromosomes highlighted with golden thread, to represent the telomeres. Telomeres are a bit like “the tips of shoelaces”, and are actually a series of DNA repeats. Every time a cell in our body divides, chromosomes can shorten at their ends, and then be rebuilt. Research has shown that unrepaired telomere shortening is one factor of the normal ageing process, amongst others, and can be somewhat malleable by a healthier lifestyle.

instagram: @moleculart_ and it’s on sale on etsy: moleculartstore.etsy.com

[beyond-mogai-pride-flags]

XYYY Pride Flag

48,XYYY syndrome: a rare Y trisomic (chromosome number) intersex variation characterized by mild-moderate developmental delay (especially speech), regular to mild intellectual disability, large, irregular teeth with delicate enamel, tall stature, and acne. Radioulnar stenosis and clinodactyly have also been associated. Children generally present typical genitalia, while hypogonadism and infertility is frequently reported in adults. It's often described as CTM karyotype with two extra Y.

-ap

[moleculart]

embroidered karyotype

with intricate stitching and vibrant threads, the piece captures the banding of the 23 chromosomes that make up our human karyotype; this karyotype in particular illustrates that of a biological female's, with XX chromosomes

A4 prints available on high quality Hahnemühle Bamboo paper (290 gsm), made with 90% bamboo fibres - with worldwide delivery!

etsy.com/shop/moleculartstore

instagram: @moleculart_