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Chapter 21: Problem 18

What are gene microarrays? How are microarrays used?

Short Answer

Expert verified
Answer: The purpose of using a gene microarray in studying gene expression is to simultaneously measure the expression levels of thousands of genes, allowing researchers to identify differences in gene expression patterns across various tissues or conditions. This can help in understanding gene function, the molecular basis of diseases, and in developing new therapies for various medical conditions.

Step by step solution

01

Introduction to Gene Expression

Gene expression is the process by which the information stored in a gene is used to produce a functional product, such as a protein. This occurs in two main steps: transcription, where the DNA sequence of the gene is copied into an RNA molecule, and translation, where the RNA molecule is used to create a protein. The level of gene expression can vary between different tissues or in response to different conditions, and understanding these differences can provide insights into the functions of genes and the molecular basis of diseases.
02

What are Gene Microarrays?

A gene microarray, also known as a DNA microarray or DNA chip, is a high-throughput technology used to measure gene expression levels simultaneously across thousands of genes. A microarray consists of a solid support, such as a glass slide or silicon chip, onto which DNA fragments representing individual genes are immobilized in a grid-like pattern. Each spot on the array contains thousands to millions of identical DNA molecules, called probes, that can specifically hybridize, or bind, to a complementary RNA molecule from the sample being analyzed.
03

Preparation of Microarrays

The first step in creating a microarray is designing the probes. Researchers choose a set of genes they are interested in studying and obtain the DNA sequence for each gene. Then, they synthesize short fragments of DNA (usually about 25-60 base pairs long) that are complementary to a specific region of each gene's RNA transcript. These fragments are then chemically attached to the surface of a solid support, such as a glass slide, in a precise pattern to create the microarray.
04

Sample Preparation and Hybridization

To use a microarray to analyze gene expression in a sample, researchers first isolate the total RNA from cells or tissues of interest. The RNA is then reverse transcribed to create a complementary DNA (cDNA) copy. This cDNA is labeled with a fluorescent dye, usually green or red, such that it can be visualized using a specialized scanner. The labeled cDNA is then hybridized, or allowed to bind, to the probes on the microarray. Since the probes are designed to specifically bind to their complementary RNA sequences, the amount of cDNA bound to each spot on the array reflects the level of expression of the corresponding gene in the sample.
05

Data Collection and Analysis

After hybridization, the microarray is scanned using a specialized scanner that detects the fluorescent signal from each spot. The intensity of the fluorescence is directly proportional to the amount of cDNA bound to each probe, and therefore, to the level of gene expression. The data collected from the microarray can then be analyzed using various statistical and bioinformatics tools to identify patterns of gene expression and to compare them across multiple samples or conditions. This can help researchers uncover important information about gene function, the molecular basis of diseases, and the development of new therapies for various medical conditions.

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Most popular questions from this chapter

Review the Chapter Concepts list on page \(556 .\) All of these pertain to how genomics, bioinformatics, and proteomics approaches have changed how scientists study genes and proteins. Write a short essay that explains how recombinant DNA techniques were used to identify and study genes compared to how modern genomic techniques have revolutionized the cloning and analysis of genes.

Compare and contrast whole-genome shotgun sequencing to a map-based cloning approach.

The term paralog is often used in conjunction with discussions of hemoglobin genes. What does this term mean, and how does it apply to hemoglobin genes?

Genomic sequencing has opened the door to numerous studies that help us understand the evolutionary forces shaping the genetic makeup of organisms. Using databases containing the sequences of 25 genomes, scientists (Kreil, D.P. and Ouzounis, C.A., Nucl. Acids Res. 29: \(1608-1615,2001\) ) examined the relationship between GC content and global amino acid composition. They found that it is possible to identify thermophilic species on the basis of their amino acid composition alone, which suggests that evolution in a hot environment selects for a certain whole organism amino acid composition. In what way might evolution in extreme environments influence genome and amino acid composition? How might evolution in extreme environments influence the interpretation of genome sequence data?

MALDI-TOF spectra can be used to identify bacteria by analyzing a colony and comparing the spectra with known profiles. Describe how this could be used to fight outbreaks of multidrug-resistant bacteria in hospitals.
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