In reality this gene is really a sequence of dna that

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In reality, this gene is really a sequence of DNA, that codes for a particular protein but we can think about a gene in terms of a gene for hair color or eye color or any number of other characteristics. Allele: One form of a gene There are multiple forms of a gene and each form of a gene is known as an allele, so I can have genes for blonde hair, or brown hair, or red hair. I can have genes for purple flowered pea plants and white flowered pea plants. So the different forms of a gene are known as alleles. Locus: The location of a gene on a chromosome If we look at all the DNA within a cell, every gene has a particular location along the chromosome that it’s found on, and that location is known as the locus Phenotype: The physical expression of the alleles (purple flowers) It could be purple flowers versus white flowers, that would be a description of the phenotype It can also be brown eyes versus blue eyes Genotype: A listing of the alleles for an individual Often for just one or two genes Technically, you could list all the alleles that an individual has for all their genes, and that would also be their genotype Within Genotypes, we can talk about two different conditions: Homozygous: The condition in which both alleles for a gene are the same Here’s a figure showing all of this information sort of together. So I have a gene for flower color, and that gene exists right in this location here. There are two forms of that gene: a purple flower allele and a white flower allele. The two alleles would be found in exactly the same location. The two different alleles would have almost the same sequence of DNA nucleotides, but there’d be some small difference, and that difference would ultimately result in a difference in flower color
We might have a genotype in which an individual has the two recessive alleles and we would say they were a/a and the two dominant alleles A/A Heterozygous: The condition in which the alleles for a gene are different The two alleles they have are different and we would write that as A/a *WE ALWAYS WRITE THE DOMINANT ALLELE FIRST* Gamete Formation 1 In thinking about genetics, it’s really important to understand how gametes form and really this is thinking about the relationship between meiosis and what that means in term s of producing the final gametes. Meiosis is the type of cell division that fundamentally leads to gamete formation Gamete Formation Rules An allele can be present in a gamete only if that individual has that allele o You cannot put alleles into your gametes that you do not contain within your own genotype. For every pairs of an alleles an individual gamete only gets one of the pairs
Let’s look at how this happens and think about meiosis. Here’s an individual who is homozygous dominant.

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