* Gametes carry one allele per gene: Gametes (sperm and egg cells) are haploid, meaning they only have one copy of each chromosome. Each chromosome carries a set of genes, and for each gene, the gamete will carry *one* allele. This allele can be either the maternal or paternal version of that gene.
* Diploid organisms have two alleles per gene: When a sperm and egg fuse to form a zygote, the zygote receives one set of chromosomes from the mother (through the egg) and one set from the father (through the sperm). This means the zygote, and all subsequent cells of the organism, become diploid, having two alleles for each gene.
* Allele combination: The combination of alleles a gamete carries for different genes is random. This means a gamete might carry the maternal allele for one gene and the paternal allele for another gene, and so on.
Example:
Let's say there's a gene for eye color with two alleles: brown (B) and blue (b). A person could have the following genotype:
* BB: Brown eyes (both alleles are brown)
* Bb: Brown eyes (one allele is brown, one is blue)
* bb: Blue eyes (both alleles are blue)
When this person forms gametes, the possible allele combinations are:
* B
* b
Therefore, a single gamete will only carry *one* allele for eye color, either B or b.
In summary:
* Gametes carry one allele per gene.
* The combination of alleles a gamete carries is random.
* It's not necessary for a gamete to carry an allele from *each* gene, only one allele for each gene that it carries.
