HowDoesLifeWork#08_The reproduction

docteur-plantes (49)in #nature • 7 years ago (edited)

The reproduction

Version française : Steemit | Busy

Aaaah what an interesting subject!

The RE-PRO-DUC-TION, very important subject, this is one of the three goals of the life (you will know them soon!).
Let’s make a rapid point: for the moment we have mainly talked about DNA with his changes allowing evolution and about primitive organisms, mainly bacteria! By the way, I told you that bacteria don’t reproduce itself but divide itself in order to multiply itself.
Yes, remind you, we can’t talk about reproduction because there is not genetics mixing!

Indeed, when there is reproduction, there is genetics mixing, let’s see why:

The reproduction is the process that allows the birth of a new individual. At the beginning this individual is an egg, I don’t talk about chicken eggs or snake eggs but well before that, when the individual is just one cell (yes everybody goes through there). This cell is called egg or zygote.

So yes, we no longer are in bacteria, now we are in eukaryotes organisms. Remember, a nucleus, a DNA cut into chromosomes, and… something that I didn’t tell you, their chromosomes are in double (this is why we say that human has 23 chromosomes pairs). So, in each cell there is DNA coil in two copies, however, they are not identical copies. Roughly speaking these two copies have the same genome but some genes don’t have the same version between the two chromosomes, these genes versions are called alleles.

A cell that has chromosomes pair is called diploid, otherwise, if a cell just has alone chromosomes it’s called haploid.

Let’s go to the reproduction!

To produce this egg, we need a male and a female, this you already know, you also know that we need a spermatozoid and an ovule for this. These two will merge during the fecundation to give the egg (zygote). That is the reproduction.

However, spermatozoid and ovule terms are specific for mammalians (at least), we talk rather of male and female gamete. They are the specifics cells of the reproduction, they are particular because they are haploid (we will see their production in the meiosis and mitosis). So, the zygote (egg) have one chromosome from the male gamete and one from the female gamete, this is that we called a genetic mixing!

The reproduction allows the mix up of the mother and father genome.

But in all of this, on which chromosomes the genetic code is read?

Genetic information will share between these two, so some genes will be read on the chromosomes from the male gamete, some other will be read on the one from the female gamete and some will be read on the two. The thing which determines that is the “strength” of the allele, one of the two version will be stronger. We talk about dominant, recessive alleles, and also codominance between two alleles.

The reproduction is an universal process among all eukaryotes organisms, whether it’s a human, a mouse, a bug, a tree, a fungus, a cactus, … A big part of the living. There are just the reproduction strategies that change between kingdoms, orders or species.

So why set up this process?

The reproduction makes it possible to speed up in evolution, indeed, the genome changes hugely at each generation (compared to bacteria which wait for the change), in addition, it’s an orientated change because we can** choose our partner** (although we do not see his alleles, we can see his strength, his speed, …).

Here we deal with reproduction implying a partner (the male and the female), consequently, we must talk about sexual reproduction. I precise this because there is a debate on the word reproduction… For some (like me) the reproduction says genetic mixing, so male and female gametes merging. For others, the reproduction would include sexual and asexual reproduction, the one which doesn’t need a partner and doesn’t allow the genetic mixing. But let’s leave that for the scientists!