2.8) Summary
DNA or deoxyribonucleic acid is the building block of life. It is a biological molecule that holds the code for making all living things. DNA is the hereditary material, passed from parent to offspring, in you and almost all other organisms. DNA matters because it is the hereditary material that holds the blueprint for life. Genes are regions of DNA that act as instructions for making molecules called proteins. Genetics is the study of genes, how they work, and how particular traits (such as eye color) are passed from parent to offspring.
Variation in our DNA allows us to adapt to our ever-changing environment. Genetic testing is used in determining carrier status for certain heritable diseases, detecting common mutations present in certain conditions, prenatal diagnosis, cancer medicine, paternity tests, crime scene investigation, susceptibility to disease, nutritional and metabolic assessments, individual traits or characteristics, ancestry information and pharmacogenetics.
Your body is made up of cells. DNA is present in the nucleus of each of your cells. It carries the instructions used for growth, development, function and reproduction. Genes contain the information needed to make functional molecules called proteins. Epigenetic changes “on top of” your genes affect the expression of genes. Epigenetic changes can turn genes up or down, on or off.
Everyone’s DNA is somewhat different – around 0.2% different. DNA is the basis for the diversity of all living things! Genetic variations make us unique. Complex traits are complex. They are a result of the combination of many genes as well as changes in gene expression and environmental factors.
Increased genetic risk or predisposition is an increased likelihood of developing a particular disease or trait based on a person’s genetic makeup. Increased genetic risk results from genetic variations that are inherited from a parent. Your predisposition can contribute to the development of a condition or trait. DNA variations that occur frequently in the population are called polymorphisms. A single nucleotide polymorphism, or SNP is a variation at a single position in a DNA sequence. Some SNPs are associated with certain diseases, traits or health factors.
Genotype is the genetic makeup of an individual or group of individuals. It can refer to a single locus, a particular trait, set of traits, or their complete genetic makeup. Phenotype is the of traits or features of an individual. Alleles are one of two or more alternative forms, or variants, of the same gene with small differences in their sequence of DNA. These variations arise by mutation, they are found at the same place on the chromosome.
Genotype frequency is the proportion of individuals in a population that possess a given genotype. It is how often we see each allele combination. Genotype frequencies vary within populations due to forces including mating patterns, genetic drift, physical distribution and migration. Genotype frequencies differ within different sub-populations due to mating patterns (sexual selection), genetic drift (random forces), physical distribution and migration.
Together, this makes up DNA science and how your biological DNA roadmap works.