Mendel was also the first to demonstrate independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the phenomenon of discontinuous inheritance. This description prefigured Wilhelm Johannsen's distinction between genotype (the genetic material of an organism) and phenotype (the observable traits of that organism). Although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. He described these mathematically as 2 n combinations where n is the number of differing characteristics in the original peas. From 1857 to 1864, in Brno, Austrian Empire (today's Czech Republic), he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. The existence of discrete inheritable units was first suggested by Gregor Mendel (1822–1884). Main article: History of genetics Discovery of discrete inherited units It is inspired by the Ancient Greek: γόνος, gonos, that means offspring and procreation. The term gene was introduced by Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1909. Therefore, a broad, modern working definition of a gene is any discrete locus of heritable, genomic sequence which affect an organism's traits by being expressed as a functional product or by regulation of gene expression. Some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. For example, regulatory regions of a gene can be far removed from its coding regions, and coding regions can be split into several exons. The concept of gene continues to be refined as new phenomena are discovered. Genes evolve due to natural selection / survival of the fittest and genetic drift of the alleles. Usage of the term "having a gene" (e.g., "good genes," "hair color gene") typically refers to containing a different allele of the same, shared gene. These alleles encode slightly different versions of a protein, which cause different phenotypical traits. Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. Some genetic traits are instantly visible, such as eye color or the number of limbs, and some are not, such as blood type, the risk for specific diseases, or the thousands of basic biochemical processes that constitute life.
Most biological traits are under the influence of polygenes (many different genes) as well as gene–environment interactions. Genotypes along with environmental and developmental factors determine what the phenotypes will be.
These genes make up different DNA sequences called genotypes. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. The RNA can be directly functional or be the intermediate template for a protein that performs a function. ĭuring gene expression, the DNA is first copied into RNA. In biology, a gene (from Greek: γένος, génos meaning generation or birth or gender) is a basic unit of heredity and a sequence of nucleotides in DNA that encodes the synthesis of a gene product, either RNA or protein. A human chromosome can have up to 500 million base pairs of DNA with thousands of genes. A chromosome consists of a long strand of DNA containing many genes. A gene is a region of DNA that encodes function.