Introduction to Medical Genetics

Introduction to Medical Genetics

• Medical genetics is a branch of medicine that deals with the influence of genes on human health and disease.
• It encompasses a wide range of aspects, including diagnosing genetic disorders, counseling families at risk, and developing new treatments.
• Genetic disorders can be caused by mutations in genes, chromosomal abnormalities, or other factors.

Types of Genetic Disorders

• Single-gene disorders: These are caused by mutations in a single gene. Examples include cystic fibrosis, sickle cell anemia, and Huntington's disease.
• Chromosomal disorders: These are caused by abnormalities in the number or structure of chromosomes. Examples include Down syndrome, Turner syndrome, and Klinefelter syndrome.
• Multifactorial disorders: These are caused by a combination of genetic and environmental factors. Examples include heart disease, cancer, and diabetes.
• Mitochondrial disorders: These are caused by mutations in the mitochondrial DNA, which is inherited from the mother. Examples include Leber's hereditary optic neuropathy and mitochondrial myopathy.

Mechanisms of Genetic Inheritance

• Autosomal dominant: An affected individual inherits one mutated gene copy from one parent. The affected individual will likely express the trait; the parent with one mutated gene copy could be unaffected.
• Autosomal recessive: An affected individual inherits two mutated copies of a gene, one from each parent. The parents are often unaffected carriers.
• X-linked: The affected gene resides on the X chromosome. Males are more likely to be affected since they only have one X chromosome. Females may be carriers.
• Y-linked: The affected gene resides on the Y chromosome, and is passed from father to son.

Genetic Testing

• Genetic testing is used to identify mutations in genes, chromosomes, or mitochondrial DNA.
• Common types of genetic tests include:
  • Karyotyping: A visual examination of chromosomes.
  • DNA sequencing: Identifying variations in the DNA sequence of a gene.
  • Molecular genetic tests: Detecting specific DNA variations.
• Genetic testing can be used to:
  • Diagnose genetic disorders.
  • Predict the risk of developing a genetic disorder.
  • Identify carriers of genetic disorders.
  • Guide treatment decisions.

Genetic Counseling

• Genetic counseling is a process that provides information and support to individuals and families who are concerned about or have a genetic disorder.
• Genetic counselors: Evaluate family history, discuss inheritance patterns, and provide information about risks and available options.

Ethical Considerations

• Genetic testing raises ethical concerns, including privacy, discrimination, and informed consent.
• Data confidentiality when handling genetic information is crucial.
• Issues of potential discrimination based on a person's genetic predisposition for a disease need careful consideration.
• Individuals need to be well informed to make informed choices related to genetic testing.

Current Research and Future Directions

• Ongoing research in medical genetics focuses on:
  • Identifying new genes associated with human diseases.
  • Developing new diagnostic and treatment strategies.
  • Improving genetic counseling practices.
  • Applying CRISPR gene editing technology.

Clinical Applications

• Medical genetics plays a crucial role in diagnosing diseases, and identifying individuals at risk.
• Genetic information is used for prenatal diagnosis, and for newborn screenings.
• Genetic information can impact treatment strategies for specific conditions.