Genetics: Variation

Genetics explains the diversity of species through variation and heredity. Variation is when individuals of the same species differ in their characteristics.
Variations can be environmental or genetic; environmental variation (like suntan) depends on where and how an organism lives, while genetic variation (like eye colour) is determined by genes.
Genes are sections of DNA that carry instructions for a particular characteristic or function.
DNA (Deoxyribonucleic acid) is a long molecule that contains our unique genetic codes. It is located in the nucleus of cells.
A set of chromosomes from each parent results in genetic variation for offspring. Humans have 46 chromosomes, 23 from each parent.
An allele is a version of a gene. Individuals inherit two alleles for each gene, one from each parent. This leads to phenotypes (the visible characteristics or traits of an organism) and genotypes (the genetic makeup or set of genes in our DNA).
Genetic mutations are changes in the DNA that can cause new characteristics to emerge. These can either be beneficial, neutral, or harmful.
Different species have different numbers of chromosomes; this is called the species’ genome size.
Charles Darwin’s theory of evolution through natural selection explains how species have evolved over time. According to him, those individuals with characteristics advantageous for their environment are more likely to survive and reproduce.
Genotype and environment also interact, as the expressed genes (phenotype) can be influenced by the environment. Stocky body shape can be due to genetic factors (e.g. genotype) and also environmental factors (e.g. eating a high calorie diet).
Genetic disorders are medical conditions caused by abnormalities in the genome. Some disorders are hereditary, meaning the genetic mutation is passed from parents to their offspring.
Genetic engineering involves modifying an organism’s genome to introduce desirable characteristics. This is achieved by inserting, replacing, or deleting genes.
Genetic diagrams and Punnett squares can help to predict the outcomes of genetic crosses. These diagrams represent the possible combinations of alleles in offspring.
Meiosis is a type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell. This is essential for sexual reproduction.
Genetic variation can be increased by sexual reproduction, mutations, and gene flow. This diversity can be important for the survival and evolution of species.
Inheritance, chromosomes, and DNA are key concepts in the study of genetics. Knowledge about these topics supports an understanding of variation, evolution, genetic diseases, and genetic engineering.