The “debunking race denial” articles may get confusing due to the unavoidable use of genetics jargon. Below is a glossary containing a few key terms that feature throughout the series. If you aren’t familiar with the basics of genetics, you may wish to keep this section at hand while reading the articles.
Deoxyribonucleic acid (DNA)
DNA is the molecule that contains an organism’s genetic code, the information necessary to build and maintain said organism.
The genome of an organism is the sum total of its DNA, the entirety of its genetic code.
A nucleotide is the smallest component that makes up DNA. Think of it as a DNA building block.
Base pairs consist of two nucleotides joined together, to form the “rungs” on the “ladder” of DNA. A nucleotide is labeled ‘nucleic acid’ in the diagram below.
Single-nucleotide polymorphism (SNP, “snips”)
A SNP is a genetic variation in one single nucleotide (DNA building block). SNPs are the most common form of genetic variation among humans, occurring approximately once every 1000 nucleotides.
A gene is a section of DNA that determines the characteristics of an organism. A sexually reproducing organism inherits genes from two parents (male and female) while an organism that reproduces asexually is genetically identical to its singular parent. Asexual organisms only “evolve” if a random gene mutation is passed onto offspring. Genes are often encoded by many base pairs, though one single base pair difference can dramatically alter the functions of a gene. Since some genes control the functions of multiple other genes, one tiny SNP variation can theoretically have a large knock-on effect.
A chromosome is essentially a package of DNA. They are found in the nucleus (center) of every single cell in the human body. Each cell contains 23 pairs of chromosomes (or 46 chromosomes in total), except sex cells (‘gametes’) which contain 23 single chromosomes. Of the 23 pairs of human chromosomes, men and women share 22. The 23rd pair, which is the sex chromosome, differs between men and women. Women have two X chromosomes, while men have one X and one Y chromosome (as shown below).
Human sperm and egg cells have only 23 individual chromosomes each, which results in the regular 46 chromosomes when the cells combine to form a child. Sperm cells also carry either the X or Y sex chromosomes that determine the sex of the child. Human sex chromosomes can occasionally align differently to XX (female) and XY (male). However, these chromosomal mutations are medically and scientifically classified as ‘disorders’ or ‘syndromes.’ This is due to their adverse effects on health. Chromosome disorders are a common cause of stillbirth, and can cause sterility or even death in adulthood. TL;DR: A chromosome disorder is not a ‘gender.’
An allele is one of two or more variations of a gene that is found at a specific location on a chromosome. Alleles are either recessive or dominant, meaning that if each parent has a different allele (variant) for the same gene, the dominant allele will be expressed, while the recessive is hidden.
Locus (plural: Loci)
A locus is a specific fixed location on a chromosome where a particular gene or genetic marker is located.
Genetic markers are specific genes or sequences of DNA that can be used to identify individuals, species, etc.
Heterozygosity is the probability that two members of the same species will have a different allele (gene variation) at a specific locus (location on a chromosome). To discover an organism’s overall heterozygosity, scientists use multiple genetic markers and multiple loci, and then calculate the average.
Fixation index (Fst)
Fst is a way to measure how much genetic material is shared by population groups. “Fst” is the proportion of the total genetic variation of a subpopulation (s) relative to the total genetic variation of the total population (t). An Fst rating of zero means total sharing of genetic material. The subpopulations are genetically identical, like clones, for example. An Fst rating of one means that there is no sharing whatsoever.
Lower Fst = more shared genes and less genetic variation.
Higher Fst = less shared genes and more genetic variation.
Genotype and Phenotype
An organism’s genotype is the sum-total of its genes, while its phenotype is the sum-total of its observable characteristics; behavior, appearance, and so on. Phenotypes are defined by the dominant genes in the genotype, i.e. the genes that physically manifest. The non-dominant genes that don’t physically manifest are still in the genotype, but are not expressed in the phenotype. For example, a blue-eyed individual may have an eye-color genotype that includes genes for blue eyes and brown eyes. However, their phenotype only has blue eyes.
Morphology is the physical structure of organisms. It includes external morphology (eidonomy), and internal morphology (anatomy).