If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:10:27

Fertilization terminology: gametes, zygotes, haploid, diploid

AP.BIO:
IST‑1 (EU)
,
IST‑1.F (LO)
,
IST‑1.F.1 (EK)
,
IST‑1.I (LO)
,
IST‑1.I.2 (EK)

Video transcript

so let's talk a little bit about how we all came into being what we see right over here this is a picture of a sperm cell of a sperm cell fusing with an egg cell so that's the sperm cell and this is an egg cell or we could call this an ovum and ovum and even this seen depicted right over here this is the end of an epic competition because this sperm cell is one of two to three hundred million that is vying for this ovum so there's two to three hundred million of these characters and they are all they're all vying for this ovum and the one that you see that's about to fuse for it this is the winner of this incredibly this is the remember two to three hundred two hundred million to 300 million sperm are trying to get here so this is a this is a major victory in to some degree we should all feel pretty good about ourselves because we are all the byproduct of that one in 200 to 300 million sperm cells that won this race getting to our mother's ovum so the sperm cell came from our father and the egg cell this is all happening this is all happening inside of our mothers the egg cell is from our mother now once this happens let's talk a little bit about the terminology so once these two fuse we call this prop or the process of them fusing we call that fertilization fertile I fertilize eight fertilization lies ation and it produces a cell that then differentiates into all of the cells of our body so you can imagine this is an important process so let's make sure that we understand the different terminology the different words for the different things that are acting in this process so thus for each of the these set each of these sex cells I guess we could say the sperm cell and the ovum these are each called gametes so this right over here is a gamete is a gamete and the ovum is a gammy the egg cell is also a gamete and as we'll see each gamete has half the number of chromosomes as a as your body cells or most of your or the somatic cells in your body so outside of your sex cells that might be in your in your oh and your ovaries or your testes depending on whether you're a female or female these have half the number so let's let's dig a little bit deeper into what I mean there so I'm going to so let's just do a blow-up of of this sperm of the sperm cell right over here so blow-up of the sperm cell and I'm not going to draw it to scale you see the sperm cell is much smaller than the egg cell but just to get a sense so let me draw the nucleus of this sperm cell so just like that if we're talking about a human being and I'm assuming your human being so that might be of interest to you this will have 23 chromosomes from your father so let's do them 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 and for the 23rd one that's going to be your sex determining chromosome so if your father contributes an X you are going to be female if your father contributes a Y you are going to be male so this is this is these are the chromosomes in the male gamete or I guess X today through the gamete that your father is contributing the sperm so this is a gamete right over here and then that's going to fuse with the egg the ovum that your mother is contributing and once again I'm not drawing that to scale so this is the this is the egg and let me draw its nucleus so that's its nucleus once again none of this is drawn to scale and your mother is also going to contribute 23 chromosomes so 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 and then she will contribute an X chromosome for the sex-determining so your sex-determining chromosomes are going to be XY you're going to be male if this was xx you are going to be female so this is also a gamete here so a gamete is the general term for either a sperm or an egg now once these two things are fused so once they are fused what do we have once they're fused then we're going to have a you could say a fertilized egg but we're going to call that a zygote so let me draw that I'll do this in a new color and I'm running out of space and I want this all to fit on the same piece all on the same screen so I'll draw it not quite at scale and so let me draw the nucleus of the zygote I'm going to make the nucleus fairly large so that we can focus on the chromosomes in it once again none of this is drawn to scale so you're going to have the 23 chromosomes from your father so let me do that 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 and 23 and then the 23 chromosomes from your mother 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 and 23 so you got that X chromosome from your mother and as you might have noticed I've drawn them in pairs so you now have a total let me let me make it clear you have 23 chromosomes here 23 chromosomes chromosomes in the sperm you have 23 chromosomes 23 chromosomes in the egg and now you have 46 chromosomes in the fertilized egg 46 chromosomes and now that we have a full contingent of chromosomes and then this cell can now keep replicating keep splitting and differentiating into all of what makes you you we call this right over here we call this a zygote zygote so one way to think about it the gametes are the sex cells that have half the number of chromosomes and the zygote is the cell that's now ready to differentiate into an actual organism that has double the number or it has that has a full contingency of korma zomes that has 46 chromosomes and you see it I made them in pairs and these pairs we call these homologous pairs and in each of these pairs this is a pair of homologous chromosomes pair of homologous homologous chromosomes chromosomes so what does what does that mean well that means that in general these two chromosomes you've got one from your father one from your mother they code for the same things they code for the same proteins but there are different variants of how they code for those pros those proteins those traits that you have so you know gross oversimplification is let's say that there was a gene let's say that there is a a gene on that one from your father that helps code for hair color well there would be a similar there'd be another variant of that gene on the chromosome from your mother that helps code for hair color as well so these are homologous chromosomes the these two chromosomes code for in general for the same things and so the zygote now has you could say it has 46 chromosomes or you could say it has 23 pairs of homologous chromosomes and this is once again this is the case for human beings if we're talking about some other species instead of 23 pairs of homologous chromosomes or 46 chromosomes in total you might be talking about 10 pairs of homologous chromosomes with or to end with 20 chromosomes in general now to help with biologists to help clarify when they're talking about the number of chromosomes for given species they introduce two words haploid and diploid and haploid haploid is referring to when you have half the full contingency of chromosomes so for human beings the haploid number is 23 so this is the haploid haploid number haploid number haploid number it is 23 for another species it would be something else and haploid is based on the prefix 8 Apple or that that's that's the prefix for single so you have kind of a single member I guess you could think of it of each of the pair's and now you have you have both of each pair you have both chromosomes or in each pair or you have the full contingency and this 46 chromosomes this is called the diploid number the diploid number for humans diploid the diploid number right over here and when people talk in general and we will speak in general when we start talking about mitosis and meiosis for a given species they will refer to the haploid number they will refer to the haploid number as n N chromosomes and the refer to the diploid number is just twice that as 2n chromosomes so hopefully this gets you familiar with some of the vocabulary around fertilization and haploid and diploid and zygotes and gametes and also makes you feel a little bit better about yourself that just to exist you at least I guess half of your chromosomes had to win an incredibly an incredibly competitive race
Biology is brought to you with support from the Amgen Foundation
AP® is a registered trademark of the College Board, which has not reviewed this resource.