Learning Objectives

• Understand the primary use of Microarrays in comparing gene transcription.
• Identify the types of genetic variations detected, such as SNPs and CNVs.
• Recognize clinical and forensic applications of genotyping.

1. Mechanism and Transcription Analysis

Microarrays consist of thousands of nucleic acid sequences arranged on a grid on a glass or silicon chip. They are most commonly used to compare gene transcription levels between two RNA samples (e.g., healthy tissue vs. tumor tissue).

• Process: mRNA from two samples is converted to cDNA and labeled with different fluorescent dyes (usually red and green).
• Hybridization: The labeled cDNA is applied to the chip. It binds to its complementary sequences.
• Result: The relative color intensity indicates which genes are upregulated, downregulated, or expressed equally across the samples.

2. Detection of Genetic Variants

When DNA is used as the sample, microarrays are powerful tools for identifying structural and sequence variations across the entire genome:

• SNPs (Single Nucleotide Polymorphisms): Identifying variations at a single base pair position.
• CNVs (Copy Number Variants): Detecting deletions or duplications of large segments of DNA.

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3. Practical Applications

Microarrays are used across multiple fields of medicine and science:

• Genotyping & Clinical Testing: Screening for genetic predispositions or diagnosing developmental delays.
• Oncology: Analyzing cancer mutations to determine the most effective targeted therapy.
• Forensics: Utilizing DNA profiling for identification.
• Genetic Linkage Analysis: Mapping the location of disease-causing genes within families.

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