What is a Nucleotide?

A nucleotide is the building block or the molecule that makes up DNA.

There are 4 variations of these building blocks in DNA (4 different nucleotides).

These 4 different nucleotides are represented by 4 letters, which are called alleles.

What is an Allele?

An allele is a letter that represents a molecule.

There are 4 different kinds of the molecules for DNA, which is why there are 4 different letters.

They are all considered nucleotides, but they are all a bit different.

So the 4 possible alleles or letters (“A” “T” “C” and “G”) represent variations in nucleotides.

This means that one person can have “A” OR “T” OR “C” OR “G” on the SNP….

What is a Gene?

The colloquial term for gene is different than the literal term. The colloquial term sees a gene as a SNP, because these are the differences in people. If you have ‘good genes’ it means you have good alleles of various SNPs. By definition, though, a gene is a whole area of your DNA that is needed to code a string of amino acids or a complete protein.

What is a SNP?

Sometimes, a nucleotide for one person is different than for another. This variation is called a SNP.

A SNP (single nucleotide polymorphism) is an area within someone’s genetics that has a variation in the letter or nucleotide.

A polymorphism simply means a change. In this case it’s a change in the nucleotide/allele/DNA letter.

So it’s a single change of the nucleotide base (from one letter to another).

At one point in history, this variation must have been new. At that time it was called a mutation.

Example of a SNP

So let’s say you have a 3 letter sequence of “ACG” on your DNA….

By the letter “C”, it could be changed in the population and some people will have “A”, let’s say…So someone can have a variation of this gene, and they’ll have “AAG” instead of “ACG”.

Major vs Minor Allele

The major allele is the common letter/allele/variation/nucleotide.

The minor allele is the less common letter/allele/variation/nucleotide.

There are usually only two possible variations, but in rare cases there is a third.

Amino Acid vs Protein

3 letters/alleles/nucleotides of DNA form an amino acid and a string of amino acids form a protein.

Variations vs Mutations

By definition, variations are simply more common than mutations. A variation will be somewhat common in the population. A mutation is rare.

Every variation was a mutation at one point in time. But if it spread through the population, it became more common and now it’s a variation, not a mutation.

Decodify Me is dealing variations, not mutations.

Why 2 Letters?

Each person has 2 sets of the same genes, one from each parent. That’s why you see 2 alleles for each SNP. A genotype is the 2 alleles from your parents.

You can have 2 major alleles, 1 minor and 1 major, or 2 minor alleles.