Journal of Population Sciences
Table 1 Glossary of the biological concepts used in the text
From: The role of genetics and epigenetics in sex differences in human survival
Term | Meaning |
|---|---|
Gamete | A mature haploid germ cell, defined as sperm cell in male and as egg cell in female |
Karyotype | The complete set of chromosomes of an organism |
Sex chromosome | A chromosome involved in the determination of the sex of an organism |
Autosome | In humans, one of the 22 chromosomes different than sex chromosomes |
Phenotype | The set of visible traits of an individual. Phenotypic variability is the result of the interaction between the genotype and the environment, which affects gene expression by means of epigenetic modifications |
Genotype | In the broader sense: the genetic make-up of an individual; in the narrower sense: the two alleles carried by an individual at a given genomic position |
SNP (single nucleotide polymorphism) | The substitution of a single nucleotide with another such that the polymorphic allele is present in at least 1% of the population |
Allele | One of two or more variant of a DNA sequence of variable length (a single base or a block of bases) at a given genomic position |
Gene expression | The process by which the genetic information contained in a gene is converted in a protein (or non-coding RNA), that affects the phenotype of an individual |
Epigenetic modification | A molecular mechanism that regulates gene expression without modifying the genotype. One of the most studied types of epigenetic modification is DNA methylation (DNAm) |
DNA methylation | DNAm consists in a reversible epigenetic modification and occurs by the addition of a methyl group to DNA without changes in the DNA sequence itself. This addition takes place at specific nucleotides of genomic DNA, i.e. cytosines that are followed by a guanine, names CpG dinucleotide. DNAm is relatively stable, as it can be inherited across cell divisions (for example during development) but at the same time can be modulated by a wide range of factors, both external to the body (for example, the lifestyle, the exposure to pollutants, the diet) (Martin & Fry, 2018; Ryan et al., 2020) and internal (for example, the hormonal set-up, the presence of pathogenic processes, etc.) (Argentieri et al., 2017; Dor & Cedar, 2018). DNA methylation is usually expressed as a continuous number ranging from 0 (all the DNA molecules of the sample are not methylated) to 1 (all the DNA molecules of the sample are methylated) |
Nuclear DNA | The DNA contained in the nucleus of a cell and organized in autosomes and sex chromosomes. Inherited from both parents |
Mitochondrial DNA | The DNA contained in the mitochondria of a cell and organized in a single circular chromosome. Inherited from mothers |
Antagonistic pleiotropy | The phenomenon by which a gene (or a SNP) controls for more traits, such that at least one of these traits has a beneficial effect on the organism early in life, and at least one has detrimental effect later in life, or vice versa |