What is Genotype and How Does It Affect Phenotype?
The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a specific gene depends on the number of copies of each chromosome found in that species, also referred to as ploidy. In diploid species like humans, two full sets of chromosomes are present, meaning each individual has two alleles for any given gene. If both alleles are the same, the genotype is referred to as homozygous. If the alleles are different, the genotype is referred to as heterozygous.
The genotype of an organism is the chemical composition of its DNA, which gives rise to the phenotype, or observable traits of an organism. A genotype consists of all the nucleic acids present in a DNA molecule that code for a particular trait. The outward appearance, or phenotype, is the result of interactions of proteins being created by the DNA. Modern DNA analyzing techniques have made it easier to identify which segments of DNA are responsible for various phenotypes. A genotype has different alleles, or forms. The different alleles are produced by mutations to the DNA, and may give rise to beneficial or detrimental changes.
Examples of Genotype and Phenotype
One example of how genotype affects phenotype is eye color. The trait for eye color could be represented with the letter âEâ. Varieties, or alleles, of that trait that are dominant will be designated by capital letters. Therefore, âEâ will represent brown eyes. Traits that are recessive are written in lower case. The allele for blue eyes is recessive to the allele for brown eyes, so we can call it âeâ. A set of parents has brown eyes. Having brown eyes only tells us their phenotype, not their genotype. The parents could be âEeâ, âEEâ, or there could be one of both. A single âEâ allele in the genotype will result in the brown-eyed phenotype, even if the parent harbors a recessive âeâ allele as well.
Another example of how genotype affects phenotype is cystic fibrosis. Cystic fibrosis is a genetic disorder that causes a thick mucus to build up in the lungs and other organs, leading to breathing problems and infections. Cystic fibrosis is caused by a mutation in a gene called CFTR, which codes for a protein that regulates the movement of salt and water across cell membranes. The normal allele for CFTR is dominant and represented by âFâ. The mutated allele for CFTR is recessive and represented by âfâ. An individual who inherits two copies of the mutated allele (âffâ) will have cystic fibrosis. An individual who inherits one copy of the normal allele and one copy of the mutated allele (âFfâ) will be a carrier but will not have cystic fibrosis. An individual who inherits two copies of the normal allele (âFFâ) will not have cystic fibrosis and will not be a carrier.
Genotype is the genetic makeup of an organism that determines its phenotype, or physical appearance and behavior. Genotype can vary depending on the number and type of alleles present in a gene or genetic location. Genotype can influence phenotype in different ways, depending on whether the alleles are dominant or recessive, and whether they interact with other genes or environmental factors.