Final answer:
The two main differences between CGH arrays and expression arrays are their applications and probe designs. CGH arrays identify genomic imbalances, while expression arrays quantify gene expression levels. Additionally, CGH arrays use DNA-based probes, and expression arrays use mRNA-targeting probes.
Step-by-step explanation:
There are two main differences between CGH arrays and expression arrays. Firstly, CGH arrays, which stand for Comparative Genomic Hybridization arrays, are used to detect and analyze copy number variations within DNA sequences. They compare differences in DNA content between different cell samples to spot genomic imbalances, which can include deletions or duplications within a genome. In contrast, expression arrays, often called gene expression arrays, measure the activity or expression levels of genes by detecting specific mRNA sequences. This can be particularly useful for comparing gene expression between, for example, healthy and cancerous cells.
Secondly, the probe design differs between these two types of arrays. CGH arrays require DNA-based probes that cover specific regions of the genome to detect variations in DNA copy number. Conversely, expression arrays use thousands of gene-specific probes that target mRNA sequences to quantify gene expression. While expression arrays can represent gene expression patterns as a heat map, CGH arrays focus on identifying which genes have alterations in their copy number.