The genotype of an organism represents its entire heritable genetic composition, encompassing the complete set of genes.[1] In a narrower context, the term can also specifically denote the alleles, which are alternative forms of a gene, carried by an organism in a specific genetic location;[2] this term was coined by the Danish botanist Wilhelm Johannsen in 1903.[3] Genotypes play a crucial role in determining an individual's observable traits, known as phenotypes.
Types of genotypes
There are three main types of genotypes: homozygous dominant, homozygous recessive, and heterozygous.[4] On one side, a homozygous dominant genotype occurs when an organism has two dominant alleles for a particular gene; for example, if the gene for eye color has a dominant allele (B) for brown eyes and a recessive allele (b) for blue eyes, an individual with a BB genotype would have brown eyes. A homozygous recessive genotype, on the other side, occurs when an organism has two recessive alleles for a particular gene. Using the same eye color example, an individual with a bb genotype would have blue eyes. The third type of genotypes, the heterozygous genotype, occurs when an organism has one dominant allele and one recessive allele for a particular gene. In the eye color example, an individual with a Bb genotype would also have brown eyes, as the dominant allele (B) masks the effect of the recessive allele (b).[5] A genotype can be identified by a Punnet square, which can help determine the probability of the genotype of an offspring, taking into account the genotype of the parents.[6]
Genotyping techniques
Genotyping, the method used to determine an individual's genotype, allows scientists to explore genetic variants such as single nucleotide variants, copy number variants, and large structural changes in DNA.[7][8] Some common techniques used for genotyping include DNA sequencing, polymerase chain reaction (PCR), and microarray analysis; many of these require amplification of the DNA sample, which consists of the production of multiple copies (millions) of a DNA sequence.[9]
Genotype vs. phenotype
While genotypes represent the genetic information of an organism, phenotypes refer to the observable characteristics that result from the interaction between an individual's genotype and their environment. For example, height is a phenotype influenced by multiple genes and environmental factors such as nutrition. It is important to note that not all genotypes directly correspond to a specific phenotype, as some traits can be influenced by multiple genes and environmental factors. Additionally, some genotypes may not have any observable effect on an individual's phenotype; in some cases, the same phenotype may or may not belong to the same genotype.[6]
The degree to which genotype affects phenotype depends on the trait. For example, the color of the petals in a pea plant is exclusively determined by its genotype, and the petals can be purple or white depending on the alleles present in the pea plant.[10] The skin color in humans, while it is determined by genotype, can darken if there is continuous exposure to the sun's rays, like with fishermen and regular beachgoers in tropical and Mediterranean countries.
Genotype and family history
Genetic pedigrees, or family trees, are visual representations of several generations in a patient's family. They show how family members are related to each other and can help identify patterns of inheritance for specific traits or medical conditions.[7] By studying the genotypes of family members, researchers and genealogists can trace the inheritance of specific traits or genetic conditions through multiple generations. This information can be useful for understanding the risk of inheriting certain genetic disorders, as well as for identifying potential carriers of recessive genetic conditions within a family.
Genealogy, the study of family history and ancestry, maximizes its research power with the construction of detailed family trees. By incorporating genetic information, such as genotypes, into genealogical research, individuals can gain a deeper understanding of their family's genetic makeup as well as their potential health risks.[11] Genetic genealogy uses DNA testing to determine relationships between individuals and trace ancestry through genetic markers. By comparing the genotypes of different individuals, researchers can identify shared genetic variants that indicate a common ancestor, and this information can be used to confirm or refute traditional genealogical research and provide new insights into family history.
See also
Explore more about genotypes
- The MyHeritage DNA test
- DNA Basics, Chapter 8: Genotypes and Phenotypes from the MyHeritage Blog
- DNA Basics, Chapter 3: DNA Expression from the MyHeritage Blog
- DNA Basics, Chapter 4: A Glossary of Terms from the MyHeritage Blog
- DNA Basics, Chapter 5: How DNA Testing Works from the MyHeritage Blog
References
- ↑ Why is it Important to Know Your Genotype and Blood Group Compatibility. Bridge Clinic
- ↑ Genotype. Scitable by Nature Education
- ↑ Johannsen W (1903). "Om arvelighed i samfund og i rene linier". Oversigt Birdy over Det Kongelige Danske Videnskabernes Selskabs Forhandlingerm (in Danish). 3: 247–70
- ↑ Genotypes. National Geographic Education. August 2022
- ↑ Genotype. StudySmarter
- ↑ 6.0 6.1 Difference Between Phenotype and Genotype. BYJU'S
- ↑ 7.0 7.1 Whole Genome Association Studies. National Human Genome Research Institute
- ↑ Introduction to Genotyping. Illumina
- ↑ Polymerase Chain Reaction (PCR) Fact Sheet. National Human Genome Research Institute
- ↑ Alberts B, Bray D, Hopkin K, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2014). Essential Cell Biology (4th ed.). New York, NY: Garland Science. p. 659. ISBN 978-0-8153-4454-4.
- ↑ Taking and drawing a family history. Genomics Education Programme. NHS