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Lactose intolerance has primarily been linked to SNPs found in the introns of the MCM6 gene which turn out to have some control over the lactase LCT gene located many thousands of base pairs away. These SNPs include:

rs4988235 and rs182549, for which the (T) and (A) alleles, respectively, form a haplotype predicting lactase persistence (thus avoiding lactose intolerance) in 77% of Europeans studied. [PMID 11788828, PMID 15114531]


A different SNP, rs145946881, known as "G/C-14010", appears to be associated with lactase persistence in sub-Saharan African populations. Two other nearby SNPs, rs41380347 "T/G(-13915)" and rs41525747 "C/G(-13907)", are also associated to a lesser degree. [PMID 17159977, PMID 23029545]
https://www.snpedia.com/index.php/Lactose_intolerance

Nucleobases:

Nucleobases, also known as nitrogenous bases or often simply bases, are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Five nucleobases—adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical. They function as the fundamental units of the genetic code, with the bases A, G, C, and T being found in DNA while A, G, C, and U are found in RNA. Thymine and uracil are distinguished by merely the presence or absence of a methyl group on the fifth carbon (C5) of these heterocyclic six-membered rings.[1][page needed] In addition, some viruses have aminoadenine (Z) instead of adenine. It differs in having an extra amine group, creating a more stable bond to thymine.[2] [...]
https://en.wikipedia.org/wiki/Nucleobase

The Western Steppe Herders are believed to have been light-skinned and had a variety of eye colors, including dark eyes and blue eyes.[26][27]

The Western Steppe Herders carried an allele that is responsible for the expression of classical European blond hair. Geneticist David Reich said that this allele first appeared in Central Asia, and that the massive migration of Western Steppe Herders brought this trait to Europe, explaining why there are millions of copies of this SNP in modern Europeans.[28] Gavin Evans has likewise stated that the "all-conquering" Western Steppe Herders were responsible for the transmission of this allele in to the dark haired native populations of Europe.[29] In 2020, a study suggested that ancestry from Western Steppe Pastoralists was responsible for lightening the skin and hair color of modern Europeans, having a dominant effect on the phenotype of Northern Europeans, in particular.[30]

About a quarter of ancient DNA samples from Yamnaya sites have an allele that is associated with lactase persistence, conferring lactose tolerance into adulthood.[31] Steppe-derived populations such as the Yamnaya are thought to have brought this trait to Europe from the Eurasian steppe, and it is hypothesized that it may have given them a biological advantage over the European populations who lacked it.[32][33][34]

Eurasian steppe populations display higher frequencies of the lactose tolerance allele than European farmers and hunter gatherers who lacked steppe admixture.[35]
https://en.wikipedia.org/wiki/Wester...s#cite_note-38

rs4988235 (T): A/G ; I have it despite being heterogeneous because A corresponds with T.

rs182549 (A) : C / T ; I have this because C corresponds with A as a nucleobase in one's dna.