Many types of computations are available in the field. Not everyone uses the same to measure the dimensions. Formulas are constant but not the measurement. Many scholars preceded distinct measurements views. The penetrance and expressivity are the measurements of the phenotypes of the same genotype.
Penetrance vs Expressivity
The main difference between penetrance and expressivity is that their quantitive measure. The penetrance can be quantitively measured, and the expressivity can not be quantitively measured. The penetrance can statistically measure, and the expressivity cannot be statistically calculated. The modified genes and some environmental factors are the reason for both penetrance and expressivity. The range of gradation is more in expressivity than in penetrance.
The penetrance is a measure of a specific gene that carries an individual portion in a population. The genotype contains a phenotype termed penetrance. The percentage of the same type of genotype that expresses the trait in the individual is the penetrance. The part of the population having a particular type of genetic change refers to the penetrance. The penetrance divides into complete, incomplete, or reduced penetrance. The mutation will lead to disease in 95% of people, and the remaining 5%will not get affected.
The expressivity is the measure of the degree of the phenotype in the genotype. The condition where the trait expressed denotes the expressivity. It measures the level of phenotype and its severity. The difference between people with the same genotype of phenotypes is the expressivity. Even people with the same genotype have a distinct type of phenotype that is called expressivity. The expression of trait varies in the range of degree in individuals is called expressivity.
Comparison Table Between Penetrance and Expressivity
| Parameters of comparison | Penetrance | Expressivity |
| Definiton | Penetrance is the measure of the part of a specific gene with an individual portion. | Expressivity is the degree of the phenotype of an individual in the genotype. |
| Quantitive measure | Penetrance is measure quantitively. | Expressivity can not be measured quantitively. |
| Statistical calculation | Penetrance has a statistical prediction | Expressivity has not statistical calculation. |
| Number of types | Penetrance has two types. | Expressivity has one type. |
| Example | Achondroplasia | Neurofibromatosis. |
What is Penetrance?
Penetrance is the proportion where an individual with a specific gene that expressed as phenotype. The penetrance has three types. Complete penetrance is the person has 100%mutation, and that affects the gene will sometimes result in disease. The people with complete penetrance is the full carrier of the phenotype. The incomplete or reduced penetrance is the likelihood of phenotype in the genotype, and it may not has a severe effect on the genotype. The partial penetrance-affected people are the half carrier of phenotype. The trait exposure varies in people. Some peoples have lifetime effect while other are not.
The penetrance is due to mutation of the gene which, might cause disease in some people. The epistatic gene, suppressor gene, and modifier genes are all effective for penetrance. Mutations are the foremost reason for the cause of penetrance in the form of inherited disease. The environmental factors are also responsible for the penetrance which affect the genome. The change in a single polymorphic allele is also a penetrance. It is complex to locate the penetrance.
The achondroplasia is a fine example of complete penetrance. In this case, the mutation will charge a risk factor for breast cancer. The BRAC1 and BARC2 are the high penetrance alleles but, they are not complete penetrance. The osteogenesis imperfecta is a perfect example of incomplete or reduced penetrance. People with this mutation have collagen in one gene, either in COL1A1 or COL 1A2. But it does not affect both at the same time. The tissue collagen strengthens the bones and muscles. The measurement of the intensity of the phenotype in the genotype is the expressivity.
What is Expressivity?
Expressivity is the degree of the phenotype of genotype in individuals. The state when the trait expressed is expressivity. The extent or the degree of the phenotype in the genotype is the expressivity. Mar-fan syndrome, Van der Wo-u-de Syndrome, and Neurofibromatosis are common syndrome by expressivity. The blue shades in the eggs vary with individuals in the expressivity.
The variable expressivity is the many numbers of people who have the same genotype with the expressed trait. But not all of them have symptoms and severity. Only a few will be affected and express. People from the same family have distinct genome mutations. The expressivity tells the range of phenotypes in that genome. The modifier genes and environment are the factors for variable expressivity. The modifier can also affect other genes in multiple ways.
The polydactyly is a fine example of expressivity. The presence of extra toes in the group of affected cats is expressivity. The extra muscle is due to the mutation of the genotype. The expressivity shows the degree of phenotype. The new finger and the cleft in the lips are all expressivity. The cis-regulatory elements result in a change in phenotype and transcript of the gens.
Main Differences Between Penetrance and Expressivity
- Penetrance is measure quantitively, and expressivity can not be measured quantitively.
- Penetrance has a statistical prediction, and expressivity has not statistical calculation.
- Penetrance has two types, and expressivity has one kind.
- The example of penetrance is achondroplasia, and the example of expressivity is Neurofibromatosis.
- The range of gradation is less in penetrance than in expressivity.
Conclusion
Penetrance and expressivity are two different terms in genetic disorders. It may show that both have a similar definition but, by comparison, you can find the differences. Penetrance is the specific genome phenotype in the individual in the whole population. Expressivity is the degree or the range of the phenotype of the genotype. Both have unique consequences on the genes. The penetrance end expressivity is affected by the modified genes, mutation, and environmental factors. Since they have distinct effects in the genome, the cause may be similar in both.
References
- https://www.nature.com/articles/gim2003356
- https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1399-0004.1997.tb02508.x