Chromosome

"Checking chromosomes, of course, we can!" Xia Linfei looked at Su Yuan strangely, "Why are you suddenly interested in this?"

"It's nothing, I'm just suddenly curious."

Actually, Su Yuan was curious whether the chromosomes in her body were XX or XY. If it were XY, genetically speaking, she would have to struggle, because her current appearance might be a false state. Currently, science could not explain why such an unbelievable thing had happened.

But if it were XX, at least she would be consistent inside and out, and there wouldn't be any repeated situations. Although this result might make her lose hope of returning to her "male body," at least there would be a conclusion, and her future life would have a direction.

So, as soon as she heard that chromosomes could be checked here, Su Yuan immediately felt an impulse.

"The human body has a total of twenty-three pairs of chromosomes, of which forty-four are autosomes and two are sex chromosomes. The sex chromosomes of males are XY, and females are XX. During reproductive genetics, males undergo meiosis to produce X-type or Y-type gametes, while females can only produce X-type gametes."

"I know that. Males provide X or Y sperm, and females provide X eggs. After fertilization, if it's XX, it's a girl, and if it's XY, it's a boy. So, whether it's a boy or a girl, apart from some exceptions related to female exclusivity, it actually depends entirely on the male, because only males have Y chromosomes."

Xia Linfei nodded with a smile, "It's good that you're a biology student; it's not difficult to understand."

"Since you're curious about chromosomes, I happen to be researching a project on human gene polymorphism. How about providing some samples for my project?" Xia Linfei suggested.

"Using my samples?" Su Yuan hesitated.

She had to be cautious about this matter. Her transformation was already bizarre. Although it could be attributed to aliens, Su Yuan actually believed it was a problem with her own genes. The human body has about 3 billion base pairs and nearly 100,000 genes. So far, the Human Genome Project has discovered about 25,000 genes, which is less than the estimated 100,000.

But who knew if her genetic information contained genes that caused sex changes?

If so, leaking it would cause big trouble.

"Reluctant to part with it?" Xia Linfei raised her eyebrows slightly and said with a smile, "This time, to conduct the gene polymorphism project, my supervisor and I, along with a few senior and junior students, have collected over 10,000 samples from the public. Adding one more won't make much difference. What are you reluctant to part with?"

Su Yuan was still uneasy and asked with feigned curiosity, "What exactly does gene polymorphism study?"

"Simply put, the gene that controls a certain trait is not immutable. While the genetic code needs to be transmitted with a certain accuracy, it also has a certain degree of tolerance. Different populations, in order to adapt to different environments, may have genes that exhibit the same trait but are not entirely identical. While maintaining the trait, the length of DNA fragments can be different, the length of repetitive DNA sequences can be different, and scattered single bases can also be different."

"For example, the gene that controls single or double eyelids. Even if they both express as genes for single eyelids, these genes might not be completely identical."

Su Yuan nodded, "I roughly understand. You mean that a gene carries the same useful information, and in the long chain of DNA, the regions that do not encode proteins or do not have important functions, these non-coding parts, due to environmental factors, undergo gene mutations, causing them to not be completely identical."

"It's pretty much like that," Xia Linfei gave her a look that said she was teachable. "These variations might be the absence, duplication, or insertion of single bases that cause changes in 'restriction enzyme' sites—thus leading to changes in DNA length; or it could be variations in the copy number of repetitive sequences; or it could be the deletion, insertion, or substitution of scattered single bases."

"Our project is to study the distribution patterns of gene polymorphism caused by these three situations."

"So, do you select specific genes for comparison?" Su Yuan asked.

"That's right. We mainly selected the genes controlling single or double eyelids, the genes for hair color, and the genes for the presence or absence of earlobes."

"I thought you were going to check all the genes!" Su Yuan breathed a sigh of relief.

Xia Linfei patted her shoulder and laughed, "Checking all genes? Do you think we're the Human Genome Project? That took several countries years to complete. Even though our research group is only studying three genes, we need to divide the personnel into three groups to work simultaneously, and the workload is still quite enormous."

"I didn't know that at first!"

Su Yuan also chuckled at herself. Human genes are incredibly complex. Just selecting three specific genes for polymorphism analysis is a massive undertaking. She was actually worried about unknown genes being exposed, which was quite laughable.

Genes cannot be easily observed with the naked eye. Xia Linfei's project only involved targeted observation of three genes. As for other genes besides these three, there was no way to trace them.

It was understandable for an outsider not to know, but she herself was worrying unnecessarily.

"You were curious about chromosomes just now, right? If you provide a sample, I, your sister, can arrange for you to see your own chromosomes!"

"Will that be too much trouble?" Su Yuan thought that Xia Linfei's research project was already so demanding, would her "curiosity" increase her workload?

"Don't worry, it's just a minor matter that can be done incidentally."

Hearing her say that, Su Yuan didn't refuse.

Seeing this, Xia Linfei brought over a laboratory-specific stool, stood on her tiptoes, and took out a disposable blood collection needle and two blood sample tubes from the cabinet above.

Upon seeing the blood collection needle and the two blood sample tubes, Su Yuan's eyes widened, and she stammered, "You… you still need to draw blood?"

"How else can we get genes without drawing blood? Come on, roll up your sleeves."

"I thought epidermal cells or oral cells would suffice," Su Yuan mumbled, but she obediently rolled up her sleeves.

She was wearing a light purple long-sleeved casual shirt. It must have been difficult for her in such hot weather, no wonder she always went to the air-conditioned library.

"It's for the experiment; we're using peripheral blood."

Her long sleeves rolled up, revealing fair and smooth skin. Xia Linfei glanced at it and exclaimed, "Su Yuan, your skin is so fair!"

Su Yuan chuckled and closed her eyes, "Draw it."

She tied on the tourniquet, gently patted her inner elbow, and the sharp needle moved closer.

Su Yuan suddenly opened her eyes, "Wait! Sister Xia, are you skilled at drawing blood? Can you do it in one go?"

Xia Linfei immediately said indignantly, "Don't you know I used to be in medical school! Drawing blood is a piece of cake! Your arm is so fair, and your veins are quite clear. I guarantee I'll succeed in one go!"

"Oh." Feeling a slight prick from the needle, Su Yuan watched with her eyes open as bright red blood flowed out of the blood collection needle, quickly filling two blood sample tubes.

"Finished."

"What's next?" With one hand pressing on the antiseptic cotton ball, Su Yuan followed closely behind Xia Linfei.

"We need to culture the cells. Each chromosome can be seen as a double helix DNA molecule coiled and condensed. To see it more clearly, we need to obtain a large number of dividing cells."

Su Yuan nodded.

She understood the principle. The blood collected contains a large number of red blood cells, which do not have genetic characteristics and no DNA. Through culturing, we can obtain other cells in the blood that have genetic characteristics and are present in larger numbers.

"How long will it take?"

Xia Linfei considered for a moment and said, "About three days. Using the cell growth stimulant 'phytohemagglutinin' at 37 degrees Celsius for three days will yield dividing cells that can be observed."