Rucete ✏ Campbell Biology In a Nutshell
Unit 3 GENETICS — Concept 20.2 Biologists Use DNA Technology to Study Gene Expression and Function
DNA technology allows researchers to investigate when, where, and how genes are expressed within organisms. Various tools such as nucleic acid hybridization, RT-PCR, DNA microarrays, and RNA sequencing help analyze individual genes and groups of genes to uncover their functions and interactions.
Studying Expression of Single Genes
- Nucleic Acid Hybridization:
- Detects mRNA using a complementary probe labeled with a fluorescent tag.
- In situ hybridization identifies gene expression patterns directly within tissues or organisms.
- Example: Studying gene expression in Drosophila embryos.
- Reverse Transcriptase PCR (RT-PCR):
- mRNAs are converted into complementary DNA (cDNA) using reverse transcriptase.
- PCR amplifies specific gene sequences from the cDNA.
- RT-PCR quantifies gene expression and detects specific mRNAs in different tissues or developmental stages.
Studying Expression of Gene Groups
- DNA Microarrays:
- Analyze expression levels of many genes simultaneously.
- cDNA labeled with fluorescent dyes is hybridized to DNA microarray slides.
- Allows comparison of gene expression between different tissues, conditions, or diseases.
- RNA Sequencing (RNA-seq):
- More precise than microarrays; RNA-seq involves sequencing fragmented cDNA directly.
- Does not rely on hybridization; instead, short reads are assembled computationally.
- Reveals quantitative expression levels and alternative splicing events across entire genomes.
Determining Gene Function
- Functional studies identify gene roles by disabling or modifying genes:
- In vitro mutagenesis disrupts genes to determine the effects.
- CRISPR-Cas9: Precise gene-editing tool widely used to knockout or modify genes.
- RNA interference (RNAi): Silences gene expression temporarily using double-stranded RNA.
- Genome-wide association studies (GWAS):
- Correlate genetic variations (SNPs) across populations with specific diseases or traits.
- Help identify genes linked to complex diseases like diabetes and cancer.
Cross-Species Gene Expression
- Demonstrates evolutionary conservation of genetic mechanisms:
- Genes from one species can function effectively in another, e.g., Pax-6 gene in vertebrates and fruit flies.
- Indicates deep evolutionary relationships and fundamental genetic similarities among diverse organisms.
In a Nutshell
DNA technologies enable scientists to study gene expression and function comprehensively. Single-gene and genome-wide analyses reveal detailed insights into gene regulation, interactions, and evolutionary relationships, profoundly impacting biology, medicine, and biotechnology.