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It seems like you might not completely understand the relationship among alleles, genes, and chromosomes, so I'll try to help you fill in some of the gaps.
You are correct about "alleles" being a "form" of a gene. However, when we talk about alleles, we typically think about them on an individual gene basis and not in comparison to other genes. In other words, we would say things like, "there are 6 possible alleles of gene Y", and not "there are 2000 total alleles on each chromosome". (The second statement might technically be true, but that's semantics.) Additionally, we don't make distinctions between "ordinary" genes and "allelic" genes. There are some cases where one allele of a gene might be silenced/"turned off" in a cell, but generally, in diploid organisms, every normal cell will have 2 alleles (copies) of each gene: one from mom and one from dad.
As a very simple example, let's consider gene X, which encodes a protein that helps determine eye color. We can pretend that there are 4 possible alleles of gene X - green, brown, blue, and grey. (In reality eye color is much more complicated than this, but let's just try to keep it simple.) You receive 1 copy, or allele, of gene X from your mom, and another copy, or allele, of gene X from your dad. Therefore, depending on what you receive from your parents, you could have 2 different alleles of gene X (say, brown and blue), or 2 of the same one (say, 2 copies of the brown allele). However, other alleles of gene X, such as the grey and green alleles, still exist in the human population even though you personally only have 2 of them. This is one way to ensure genetic diversity in a population, which is advantageous for all sorts of reasons.
The specific alleles of a given gene are transmitted through the process of meiosis. If you're not familiar with it, there are many good videos out there that explain the process very well. I hope this helps!
Comment by RegZaaa23 at 19/11/2021 at 12:44 UTC
1 upvotes, 1 direct replies
It helped a lot thx man!!