Meiosis, Gametes, and the Human Life Cycle
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- เผยแพร่เมื่อ 12 มิ.ย. 2024
- We know that your body produces more cells through mitosis. But where did your very first cell come from? It can't have been mitosis, because mitosis needs a cell to start with. As it turns out, meiosis and subsequent fertilization are the culprits! Meiosis is another kind of cell division, but it is different from mitosis. How is it different, pray tell? Watch and find out!
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my teacher tried explaining this today and i was so confused but this professor always helps me out when i’m confused as hell
You know that Professor Dave had all the time he needed to make the video as clear as possible, right while your teacher hadn't. Also maybe the fact that your teacher explained this topic made you understand it better listening it a second time. Well it did months ago but still I don't know why the hell I wrote this when you likely aren't going to read it and it has passed so much time that you probably have 100 percent forgotten about this comment. Damm what a huge waste of time.
@@klb9672 it wouldn't had been a frustrating 🥴 note if u hadn't wasted 50% more words to explain your note as useless
Well it's not easy being a teacher,and as a student we all have to understand what hardworks they do for us.😊
I'm kinda confused 😢
Several khan academy videos, ameoba sisters videos, some other random popular dude on the internet for science videos, hours. And you’ve just explained it better it 10 minutes
5 1-hour lectures and I learned this more quickly in 2 videos totaling less than 20 minutes. Incredible, thank you professor Dave!
I think this is by far the best video I’ve seen explaining this topic! Thank you!
I really love your content.
I visit your page every-time I have a hard time understanding a topic.
These videos are so helpful!! I watch all your videos before a Bio exam!
This is very helpful thank you for posting Professor Dave
Thanks! This helped me a lot in this subject; especially for tests!
Would love to see a part about aneuploidy and nondisjunction!
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Thanks prof, I can finally smile during today's lecture after I watched your video.
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this was really helpful thank you! I have a test today for my anatomy lab, so thank you so much for explaining this!
Thank you so much, your videos are very helpful!
Professor Dave, you get it. You know just what we need to learn. Thanks for making your videos easy to understand and an effective way of learning.
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Thank you professor Dave!
Very nicely explained
Thank you so much after 4 years reading this only now I clearly got to understand..
thank you professor dave!!
Thanks, Dave!
Really Thanks 🤩 I understood it all
Thank you.
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you explain so much better than my biology teacher, thanks alot 😁😁😁😁
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This video helps summarize Meiosis in a concise way. Nice video! This is helpful for my Genetics class.
YOU TEACH BIOLOGY TOO?! GEEZ. you're a god.
Thanks
What about the significance of mitosis for the fertilization process? Cell repair process? And for budding process?
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that was supposed to be explain
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This video is full of information. I managed to understand the meiosis thing. But still, You have blown my mind.
According to your video all animals begin with a single cell that is made throw meiosis that is a type of cell division. Then you haven't answer to you question."where does this single cell come from?" What I am trying to say is that your question is where does life come from. None knows
Professor Dave Explains but still, gametes are cells with DNA inside. where this sperm and egg came from.
I know they were created some where in the prostate and the ovaries. But How?
meiosis!
Actually, if we are going as far back as meiosis creating gametes that join in a process of fertilization creating the first new organism's cell, the process actually can go a bit farther back starting with mitosis! Oogonia and spermatogonia undergo mitosis to form the primary oocyte or spermatocyte, respectively. The only question I have is: is there really a telophase at the end of meiosis 1 if no nucleus reformation is necessary since meiosis 2 follows?
of course there is
oocytes arrest at metaphase II, so fertilization takes place when the there is only on polar body and the is another division left?
Very helpful , your explanation is so clear, can u come and teach me biology in my high school?lol
I hope someone can answer this because I have seen no video that explains how 4 haploid cells that have crossed over and have already undergone recombination become a diploid zygote?
well it's not that four haploid cells generate a zygote, it's simply that meiosis produces four haploid gametes, in both males and females, so one somatic cell will make either four sperm cells or four egg cells. then, totally separately, a sperm cell and an egg cell fuse to become a diploid zygote, because n + n = 2n.
@@ProfessorDaveExplains can u please make a video to explain. Like zygote is formed with 46 chromosomes 23 from each parent. Then after fertilization meiosis takes palce? 😭😭😭😫😫😫 i am sooo confused.
No, after fertilization mitosis takes places. Meiosis forms the gametes.
After crossing over what is ghe use it continues to 4 daughter cells remaining in the same body. Or does it enhance different body parts. Please help me I am soo confused 😫😭😭😢😢
This topic is kind complicated, you will take it more in details in embryology. There you will understand the meiosis much better... I actually understood meiosis once i took embryology.
Anyway, those 4 haploids cells produced from meiosis are the ones which form the gametes and only one of them will be used during fertilization. Meiosis has nothing to do with enhancing body parts, growing, etc..
Meiosis is just for sexual reproduction. MITOSIS is the one used to grow and enhance different body parts.
A male germ cell in meiosis produce 4 spermatids(4 haploid cells) which will later mature in sperms. There are millions of sex cells in the testis that undergo meiosis and as a result there will be produced millions of sperms but only ONE sperm will fertilize the egg cell.
In female egg cell is also produced by meiosis, the difference is that females will produce only ONE mature egg during meiosis. 3 out of the 4 haploids cells produced in meiosis will degenerate thus forming only a SINGLE egg cell.
Again,this is how gametes are produced.
As i said, when you take embryology; spermatogenesis and ovogenesis you will get the point.
*For now, if you still haven't taken embryology, you can just know that MEIOSIS PRODUCES GAMETE CELLS*
Good
This is best explanation of Meiosis and sexual reproduction I have seen so far. Much kudos to Prof. Dave
Sir ya tamam batay assignment ma add kar saktay ha
Hmm... Around the 6-Minute mark you state that maternal and paternal chromosomes play a role in Prophase I and Metaphase I. But doesn't Meiosis produce the gametes which only upon fertilization combine maternal and paternal chromosomes?
The cells undergoing meiosis have both sets of chromosomes, they must be separated in meiosis 1.
Damn, I was intrigued regarding the DNA part. My mother is a mathematic savant while I don’t even have the brain cells to calculate tough math questions. 😂 Thanks for the lesson, Professor Dave. It cleared up my confusions.
So the result of spermatogenesis are sperm cells with 23 chromosomes, each with only 1 chromatid (so in total 23 chromatids). And the result of oogenesis is a primary oocyte with 23 chromosomes each with 2 chromatids (so in total 46 chromatids). But when fertilization happens 23 chromatids are lost to the polar body, leaving 23 chromatids to combine with the 23 chromatids of the sperm cell. 23+23= 46. How do you get the 92 chromatids that are needed to form the 46 chromosomes (each with 2 chromatids) that a zygote supposedly has? I don't get it:(
Me tooo please help
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@@ProfessorDaveExplains thank you so much. It was very helpful 😄💜
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Finally understand the difference between mitosis and meiosis. You're the best
Is cross over always random?
I got a question Professor. I heard about centrioles, an organelle only found in animal cells. However, as I dig deeper, centrioles are important in forming spindle apparatus during cell division. As i was starting to understand all about this stuff, I'm kinda inquisitive about what that teacher said about centriole only found in animal cells. But wherever part of that google world I check, centrioles are always found in either human or animal cells. So, my question is, is there really a different name of a human centriole from an animal centriole? I would love to hear your answer about this thing, i would appreciate it a lot. Thanks
Well, humans are animals, so humans would of course have animal cells. Unless you heard somewhere that centrioles are absent in humans... Did you hear that somewhere? It's been a while since I learned this in school.
Damm! I don't understand that if we have gamete it's from by meiosis and that includes both the parents characters? How? And during fertilization they from a 46 diploid cell?!
I attempt assignment of zology about miosis 1in male to jo is ma miosis Ki batay ha bas Wo add kar do
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@3:58: the two red X-shaped double-chromosomes right after DNA replication, and the two red X-shaped double-chromosomes in the left haploid cell at the end of Meiosis (1), are they NECESSARILY the same chromosomes? I mean, I'm missing some randomness in this picture. At the beginning of Meiosis (1) it's not yet clear which one of the two haploid cells any chromosome will end up in, right? The colour coding, however, kind of suggests that, doesn't it? It also suggests that the two red chromosomes have some common property, which they don't, do they? [Of course the same comment/question could be made for the blue chromosomes]
I have question :
I know meiosis for Sperm and egg which are haploid cell. As u said at end of video , Sperm and egg combine and fertilization occur and after that Mitotic occur
But how premeiotic cell is diploid and have parental homologous and maternal homology
Supposed this sperm still didnot fertilize egg yet
I'm not an expert but as i know, the homologous chromosomes(paternal and maternal) that undergo crossing over when producing sperm or eggs(during meiosis 1) are the chromosomes which were passed by their own parents.
There are 23 pairs of chromosomes( 46 total, 23 paternal and 23 maternal) in every cell of the body
Let's say someone produces a gamete. During profase 1 'paternal' and 'maternal' chromosomes(homologous) swap a section of DNA, these maternal and paternal chromosomes actually belong to the parents of the person producing the gamete.
Thanks brother... this helped me a lot 🥹
thanks, professor, btw you were so formal back then lol
I want a lyric to that starting song(...Science staff Professor Dave explains)
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Hi
@@ProfessorDaveExplains lol
ok but his intro is so fun-
4:26 "At prophase, each chromosome already duplicated". What cell is that and how did the chromosome duplicate?
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How do the resulting haploids form meiosis ii have the same number of chromosomes as the resulting haploid from meiosis i? Is it because a single chromosome can be recognized as both two sister chromatids or one single chromatid depending on the stage in replication?
the sister chromatids are identical, so when they are pulled apart it's still the same number of chromosomes, just now unduplicated
@@ProfessorDaveExplains That's what I was thinking, thank you!
So: sperm meets egg and they make zygote. Then The zygote is divided to four parts(n cells).
And Then? Does these 4 cells Combine together to make 2 diploid cells which starts mitotic dividing and makes new human?
Or what exactly happens right after meiosis.
The zygote is already diploid, it divides by mitosis.
Heh. Now I finally got it..
Meiosis happens later (before birth or during pubertity) and it Have nothing to do with fertillization..
I always thought fertillization process includes meiosis somehow 😅
@@wepe187 lol.. this was the same doubt puzzling me for years. NOw its clear. ha ha
But if each daughter cell is now a unique haploid of its own, how does that for a human? Does one combination dominate? And how do the cells go from this point to mitosis? Do new "sister" dna strands appear? That's a 4 cell organism, we are billion cell organisms... what is the "missing piece"? I understand both processes now, BUT how do they go from 4 cells to the variation end point where all we need is mitosis to maintain a human's various organs and cells?
The gametes undergo fertilization and the zygote is diploid. The rest is mitosis. This is all explained very clearly.
What happens after 4 cells are produced? Do the continue mitosis if yes then why each of them has 23 chromosomes?
the gametes undergo fertilization
In simple terms; father makes 4 cells, each is called a gamete (haploid), mother makes 4 cells each a gamete also. Then one gamete from each parent join together to form a zygote which is, therefore, diploid. The remaining gametes just die off and the zygote will continue to grow by mitosis. haha.
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one day definitely!
Question!: So, when you have 46 Unduplicated chromosomes in the nucleus, what you have is 23 chromatids from your mother and 23 chromatids from your father correct? Are they only in the X shape as chromosomes once DNA replication has occurred? Therefore, you have 46 X's so to speak? After replication you have 92 chromatids = 46 pairs of chromosomes? In Meiosis I see that you have 23 duplicated chromosomes and the ploidy number is "n". Im confused by that because im imagining that there is still 23 X-shaped chromosomes in each of the cells produced, and so thats 46 chromatids..I think im thinking about it wrong...
I know thats a lot, sorry! but thanks in advance
23 pairs of chromosomes so 46 chromosomes at all times, which can either be unduplicated or duplicate sister chromatids in the familiar X shape.
HELPP!! I don't get meiosis. first of all, egg and sperm forms zygote. then the zygote divides to 4 daughter cells. but the biology book says that the four daughter cells are gametes, which is sperm and egg. it obviously can not be sperm or egg, because it has already fertilized in the first place!!
no no, meiosis is what produces the egg and sperm. once the zygote forms, it only undergoes mitosis.
1:03, 4:32, 4:46, 5:11 - 5:26!, 5:59 indep. assort, 8:09 2^n n=haploid #, so humans can have about 8million different gametes.
4:30
at the end of the meiosis I, we have 2 diploid daughter cells, not haploid. at the end of Meiosis 2 we will have 4 haploid daughter cell. (6:38)
No, they are haploid. The homologous chromosomes were separated.
@@ProfessorDaveExplains what about the tetrad? In meiosis 1 there will be 92 so at the end there is 64 again and then when they separate at the end of meiosis 2 there will be 32 in each
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Prophase 1 need better elaboration😕
Meiosis produces "daughter cell" or "haploid gametic cells"??
Sir will you please explain slowly
well i can't change the clip in any way, but just watch it again and/or pause when you want to stare at something!
Professor Dave Explains OK sir thank you
Click the wheel on the bottom right side of the video. There you can set the speed of the video. Put it on .75
It'll help
Do people with Swyer syndrome also still have meiosis?
I don't think so. Meiosis occurs in the ovaries and testis, and people with Swyer syndrome don't have either. From my understanding, Swyer is when the Y chromosome screws up and doesn't turn someone male due to a defective or missing SRY gene. I may be wrong but I remember learning in high school that meiosis occurs in the ovaries (to produce eggs in females) and the testis (to produce sperm in males), so you need either of those organs to do meiosis and make gametes.
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I'm slowly getting it, thanks but! You say all cells have DNA. Do red blood cells have DNA? Thanks for these videos.
No,matured RBC donot have nucleus..so it has no dna
Just now i got to know sister chromatids are identical to one another and it only looks like X’s when it’s already duplicated. How dumb am i.
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Wao👌
1:31 isn't it -> 1 chromosome made up of 2 chromatids? Why is it 46 unduplicated chromosomes although chromatids haven't replicate? i thought that is is 46 chromatids-> duplicate x2 = 92 chromatids = 46 chromosomes (92/2 since 1 chromosome consist of 2 chromatids)
sure, that's correct
I DONT UNDERSTAND
watch one more time!
try to be consistent with use of colors. its very confusing when you reach understanding meiosis.thanks
i don't know what you're referring to
Gametes are also cells.
It still makes no sense to me
Hahaha you used the Linux mascot as the penguin :))
Mitosis ...=Normal Jindagi
Meosis= Mentos Jindagi😂
😂😂😂😂