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  • Sperm cells are the smallest cells produced by the human body, at only 50 micrometers long.

  • But a single sperm cell contains a complete copy of all the data found on 23 chromosomes,

  • which can be hundreds of megabytes of information.

  • Even your fancy new microSD card can’t compete with that kind of storage density.

  • And thanks to a study published this week in the journal Cell Metabolism, we now know

  • that sperm carries not just genetic information, but epigenetic information as well.

  • Your DNA contains most of the instructions for making you, organized into genes, and

  • all those genes together make up your genome.

  • But even though each cell gets a complete copy of that genome, it only needs to use

  • certain parts -- and it figures out which parts based on your epigenetic information.

  • It needs the help, because your DNA is an incredibly complex molecule -- and it’s

  • also really, REALLY long.

  • If you stretched out a single molecule of your DNA? It would be two meters long!

  • So, how do you squeeze a two meter long molecule inside the nucleus of a cell? You wrap the

  • DNA tightly around a long filament of protein called histone. Coiling the molecule into

  • a spring like that compresses it down.

  • But it also introduces a new problem: your DNA is wrapped SO tightly around the histone

  • that your cell can’t access most of your genetic information anymore.

  • So, in addition to histone and DNA, you also have epigenetic markers.

  • Epigeneticliterally meansabove your genes.” And those epigenetic markers

  • sit right on top of your DNA.

  • They tell the cell where to coil the DNA tighter, and where to let it unspool. Unspool the DNA,

  • and the cell can read the genes in that location. Tighten up the coil, and the genes there won’t

  • be expressed in that cell.

  • It’s part of the reason that, say, a neuron becomes a neuron, and not a muscle cell -- those

  • cells carry different epigenetic data.

  • The neuron reads the parts of your DNA that tell it how to be a neuron, and not the parts

  • that would tell it how to be a muscle cell.

  • That’s how powerful epigenetic markers can be -- and they can change based on how you

  • live your life. Your weight, diet, stress levels, and even your moods can alter those markers.

  • We also know that theyre inherited, but for a long time, geneticists thought that

  • sperm cells were too small to contain both the genome AND the epigenetic information of the donor.

  • And while some studies in the past have suggested this might not be the case for mice, there

  • hasn’t been much research into the human side of things.

  • Sperm cells were believed to be inert carriers of DNA, so scientists just...never really

  • looked into it.

  • Until now! In this study, a group of researchers from

  • the University of Copenhagen were specifically looking at the differences in the sperm cells

  • between lean and obese men.

  • And what they discovered was that those sperm cells not only contained epigenetic markers,

  • but they contained DIFFERENT epigenetic markers depending on whether the donor was lean or

  • obese.

  • Specifically, there were differences at the gene regions associated with appetite control.

  • The team compared sperm cells from 13 lean men and 10 obese men, and then tracked 6 men

  • who were going through weight-loss surgery, to see how the weight loss affected their sperm.

  • On average, five thousand changes to sperm DNA were found between samples from before

  • the surgery and a year after.

  • Well, the differences in those sperm cells were found not in the structure of the DNA

  • or in the histones -- they were in a different, related kind of molecule, called small RNA.

  • And turns out that small RNA can also act as an epigenetic marker, by telling the cell

  • which genes to turn on and off.

  • For decades, scientists believed that RNA molecules only functioned as messenger molecules,

  • carrying information to different parts of your cells.

  • Then, in 1998, geneticists discovered that some RNA molecules play a huge role in silencing

  • your genes. They can prevent genes from being expressed -- making them an epigenetic marker.

  • They detect certain groups of instructions in your DNA, and then just clip onto them,

  • so the cell can’t access them.

  • And in the men in the study, they clipped onto different parts of the DNA, depending

  • if they were lean or obese.

  • Women who want to have a child hear a lot of health recommendations, both before and

  • after they get pregnant: things like maintain a healthy weight, don’t smoke, stay away

  • from alcohol and drugs -- because that could potentially affect the health of the child,

  • even before conception occurs.

  • And at least part of the reason is that these things can change epigenetic markers, which

  • then get passed on.

  • But according to the lead author on the study, these results tell us that prospective fathers

  • might want to take care of themselves, too.

  • Thanks for watching this episode of SciShow Space News, and thanks especially to our patrons

  • on Patreon who help make this show possible. If you want to help us keep making episodes

  • like this, just go to patreon.com/scishow. And don’t forget to go to youtube.com/scishowspace

  • and subscribe!

Sperm cells are the smallest cells produced by the human body, at only 50 micrometers long.

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健康如何影響精子 (How Health Affects Sperm)

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    PPPqqq 發佈於 2021 年 01 月 14 日
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