Partial or complete fusion of the eyelids by webs of skin. 


A thread-like structure in our cells that contains all our genetic characteristics. One chromosome contains many genes. In humans, there are 23 pairs of chromosomes altogether, 1 pair is inherited from each parent.


Inwardly curved fingers or toes.


Also known as a split hand/split foot malformation. Deficiency or absence of one or more central digits giving rise to a “claw-like” appearance. 


An unborn offspring in the early stages of human development after the fertilisation of female egg cells by male sperm.


The most basic functional unit of inheritance. Made up of DNA and provide instructions to cells to make proteins.


A doctor who diagnoses and manages patients with genetic disorders.


A doctor who specialises in the diagnosis and management of disorders of the female reproductive organs.


A blood-filled dilated vagina due to menstrual blood in the setting of an anatomical obstruction.

Hypomorphic allele

A variant leading to partial loss of gene activity.

Incomplete penetrance

A pathogenic variant may not necessarily result in disease. Frequently seen in autosomal dominant conditions where some heterozygous carriers are asymptomatic.

Incomplete penetrance

A pathogenic variant that may not necessarily result in disease. Frequently seen in autosomal dominant conditions where some heterozygous carriers are asymptomatic.

Missense mutation

A change in one DNA nucleotide which may result in the substitution of one amino acid for another in a protein produced by a gene. 

Null allele/null mutation/null variant

A variant that lead to minimal/absent production of functional protein.


Fewer than five fingers or toes. 


A doctor specialising in managing eye diseases.

Paediatric oncologist

A doctor who specialises in childhood cancers.


One or more extra fingers. 


This type of inheritance is described in families in which consecutive generations are affected by recessive disorders, hence appearing to follow a dominant inheritance pattern. It is more likely to occur in families with consanguinity or in recessive disorders where there is a high carrier frequency, such as in an isolated population.


Enlarged dental roots.


Either a disproportion of the length of the proximal limb (usually shortening) or deformity affecting shoulder and arm or hip and thigh. 


Fusion of two or more digits.


A drug that does not have any active ingredients.

Splicing defect/splice site mutation

A precursor messenger RNA (pre-mRNA) is produced during DNA transcription. The pre-mRNA contains both exons (segments of DNA coding for a protein) and introns (segments of DNA not coding for proteins), which needs to be processed to form mature mRNA in preparation for translation. To achieve this, introns are removed through a process called splicing so that only exons remain in the mRNA. Splice site mutations cause one or more introns to remain in the mRNA, potentially leading to the production of abnormal proteins. 


A doctor who specialises in disorders of the urinary tract and male reproductive organs.

Variable expressivity

A pathogenic variant associated with varying degrees of phenotypic severity among individuals within the same family.

X-inactivation (X-lyonisation)

A random process in females to ensure there is only one functional copy of X chromosome in each cell. This results in some cells having active maternal X chromosome while other cells have active paternal X chromosome.