[Medical genetics] Introduction

Medical geneticists specialise in diseases of the karyotype and genotype of a patient.
There is significant overlap with paediatrics.
This is a pathology discipline.  

 

Etymology

Latin medicus, medica, medicum = healing, curative, medical
Ancient Greek γένεσις (génesis) = origin

 

Subspecialties

• Cytogenetics
• Molecular genetics

 

Responsibilities

• Counselling patients and their relatives about the implications of a diagnosis and the risks of inheritance
• Determining the type and number of chromosomes 
• Making prenatal diagnoses 
• Predicting the severity of disease from the genotype (e.g. counting gene duplications, microsatellite expansions, etc.)
• Sequencing a particular gene to identify mutations
• Screening for a known DNA sequence (e.g. known gene mutations)

 

Investigations 

• Deletion analysis  
• Dosage analysis 
• Linkage analysis   
• Methylation analysis 
• Microsatellite analysis

Screening for known mutations

• Comparative genomic hybridization (CGH) 
• Karyotype test
• Fluorescence in situ hybridization (FISH)

• Chemical cleavage of mismatch
• Multiplex ligation-dependent probe amplification (MLPA)
• Next generation sequencing (NGS) 
• Oligonucleotide ligation assay
• Polymerase chain reaction (PCR)
• Reverse Transcriptase-Polymerase chain reaction (RT-PCR)
• Southern blot analysis  

Identifying unknown mutations

• Comparative genomic hybridization (CGH) 
• Karyotype test

• Chemical cleavage of mismatch
• Denaturing Gradient Gel Electrophoresis (DGGE)
• Heteroduplex analysis
• Multiplex ligation-dependent probe amplification (MLPA) 
• Next generation sequencing (NGS) 
• Oligonucleotide ligation assay
• Protein truncation test
• Restriction fragment length polymorphism (RFLP)
• Reverse Transcriptase-Polymerase chain reaction (RT-PCR) 
• Single Strand Conformational Polymorphism (SSCP) 

 

History taking 

The history involves being able to construct an accurate and detailed family tree with all available information.

 

Physical examination

 The physical examination should be guided by both the presenting problems, and the suspected diagnoses. Many genetic diseases are strongly associated with a characteristic phenotype. A facies is a physical appearance which strongly points to a diagnosis.

 

Genetic diseases sorted by frequency

 

Inborn genetic diseases