Looks are not superficial and skin deep but an outward expression of what lies underneath. Our genetic make-up (genotype) influences our physical characteristics (phenotype) including our height & eye colour. But in the genetic disorder Marfan syndrome, these characteristics are very variable. Why?

What’s the difference – Genotype and Phenotype?

If you or your family member have a genetic diagnosis of Marfan syndrome you may be familiar with these two terms that are often used, but what do they mean?

Genotype refers to the genetic makeup of an organism, including humans. The genotype is the genetic blueprint that influences the way in which an organism develops and functions. Genetic testing is needed to determine a person’s genotype.

Phenotype refers to the observable physical and physiological characteristics of an organism e.g. hair colour, metabolism. The phenotype is the expression of the genetic instructions within the genotype along with the influence of environmental factors like diet and lifestyle.

Genotype and Phenotype in Marfan syndrome

MFS is caused by a gene change on the FBN1 gene but as you know, the phenotype of Marfan syndrome is very variable – people with Marfan syndrome have very different signs/symptoms and will be affected by their genetic change in different ways.

Research is ongoing (including in our own Sonalee Lab) to try and establish some correlations between genotype and phenotype so that in the future we might be able to predict more accurately the issues that an individual might face.

For example – if the gene change is in a certain position on the FBN1 gene we may be able to predict phenotype more accurately. e.g. a gene change in one position might mean that eye problems are more common while another gene position might indicate a higher risk of aortic problems.

Marfan Trust, a CIO registered as a charity in England in Wales with charity number 1198847 at: c/o 24 Oakfield Lane, Keston, Kent, BR2 6BY. Contact us at [email protected] or by phone on + 44 (0)333 011 5256
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