MI Unit 2

Study Guide: Genetic Testing and Screening

Lesson 2.1: Genetic Testing and Screening

Overview:

- Genetic testing is used to diagnose, predict, or identify carriers of genetic disorders.

- It involves analyzing DNA to detect abnormalities in genes or chromosomes.

- The Smith family case study introduces the importance of genetic screening during pregnancy.

Key Concepts:

1. Genes, Chromosomes, and DNA

- 23 pairs of chromosomes (22 autosomes + 1 sex chromosome pair)

- Genes are DNA segments that code for proteins, influencing traits and diseases.

- Chromosomal abnormalities and defective genes cause genetic disorders.

2. Types of Genetic Disorders:

- Single-gene disorders: Caused by mutations in one gene (e.g., Sickle Cell Anemia, Cystic Fibrosis).

- Multifactorial disorders: Result from multiple genes and environmental factors (e.g., Breast Cancer, Diabetes).

- Mitochondrial disorders: Caused by mutations in mitochondrial DNA, inherited from the mother (e.g., Leber’s Hereditary Optic Neuropathy).

- Chromosomal disorders: Caused by missing or extra chromosomes (e.g., Down Syndrome/Trisomy 21).

3. Genetic Testing Methods:

- Carrier Screening: Identifies individuals carrying a recessive genetic disorder.

- Preimplantation Genetic Diagnosis (PGD): Screens embryos for genetic disorders before implantation.

- Fetal Screening/Prenatal Diagnosis: Uses amniocentesis or chorionic villus sampling (CVS) to detect disorders in the fetus.

- Newborn Screening: Tests infants for genetic disorders after birth.

4. PCR (Polymerase Chain Reaction):

- A laboratory method to amplify DNA.

- Steps: Denaturation (unzipping DNA), Annealing (binding primers), and Extension (copying DNA with Taq polymerase).

- Used in genetic testing for diagnosing diseases.

5. Gel Electrophoresis & Restriction Enzymes:

- Used to identify mutations by separating DNA fragments based on size.

- Helps diagnose genetic conditions by detecting specific gene variations.

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Lesson 2.2: Our Genetic Future

Key Topics:

1. Gene Therapy:

- Replaces defective genes with healthy ones using vectors.

- Types of vectors: Retroviruses, Adenoviruses, Liposomes, Naked DNA.

- Challenges: Targeting correct cells, integrating genes permanently, ensuring safety.

2. Designer Babies:

- Ethical concerns over genetic enhancement.

- Potential to select traits beyond disease prevention.

3. Reproductive Technologies:

- Sperm Sorting: Selects sperm carrying X or Y chromosomes for gender selection.

- Preimplantation Genetic Diagnosis: Screens embryos for genetic conditions before implantation.

4. Cloning:

- Reproductive Cloning: Creating a genetically identical organism.

- Therapeutic Cloning: Cloning body parts for medical purposes (e.g., growing organs for transplants).

Conclusion:

- Advances in genetics allow for early disease detection and treatment.

- Ethical considerations must be addressed as technology progresses.

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Flashcards:

1. Q: What is genetic testing?

A: The use of molecular methods to diagnose, predict, or identify carriers of genetic disorders.

2. Q: What are the four types of genetic disorders?

A: Single-gene, Multifactorial, Mitochondrial, Chromosomal.

3. Q: What is a karyotype?

A: A picture of an individual’s chromosomes used to detect chromosomal disorders.

4. Q: How does PCR work?

A: DNA is amplified through denaturation, annealing, and extension.

5. Q: What is gene therapy?

A: A treatment that replaces faulty genes with functional ones.

6. Q: What are restriction enzymes used for in genetic testing?

A: To cut DNA at specific sequences, helping identify mutations.

7. Q: What is Preimplantation Genetic Diagnosis (PGD)?

A: Screening embryos for genetic disorders before implantation.

8. Q: What is the difference between reproductive cloning and therapeutic cloning?

A: Reproductive cloning creates a new organism; therapeutic cloning creates body parts for medical use.

9. Q: What is the purpose of newborn screening?

A: To test infants for genetic disorders shortly after birth.

10. Q: What are the risks of fetal screening methods like amniocentesis and CVS?

A: They carry a small risk of miscarriage.