Are half the genes inherited from the mother and half from the father? Do environmental factors influence a person's observable physical traits? Here are some interesting questions about genetics.
Genotype and phenotype - what are they?
The genotype is the genetic make-up of an organism, the complete set of genes inherited from its parents. Did you know that half of the genes are inherited from the mother and half from the father?
The term phenotype, on the other hand, refers to a person's observable traits such as height, eye colour or blood type.
What determines the phenotype?
The phenotype is determined by its genotype and environmental factors. In fact, due to the environment, organisms with identical genotypes may express different phenotypes. The branch of science that studies this area of genetics is known as epigenetics.
What are Mendelian and polygenic traits?
An Austrian monk named Gregor Mendel established a set of general patterns for the transmission of genes from parent to offspring: Mendelian inheritance. These patterns refer to the type of inheritance that can be understood simply as the consequence of a single gene.
Mendel established alleles, each of the alternatives that a gene of a character may have, and its dominance or recessivity. Dominant genes dominate against a different gene, while recessive genes are not expressed in the presence of a dominant allele.
For years, this model was taught with one example: eye colour. There is now scientific evidence that the inheritance of this trait is not so simple, as up to 16 genes can influence eye colour. Such traits involving two or more genes, which do not follow Mendelian inheritance patterns, are called polygenic. Contrary to popular belief, most human traits are polygenic, with skin colour and height being other examples.
Interesting, isn't it?
