Final answer:
A researcher can use methods like qPCR, RNA sequencing, and microarray analysis to calculate the original number of targeted mRNA molecules in a cell.
Step-by-step explanation:
A researcher uses various methods to calculate the original number of targeted mRNA molecules present in a particular cell. One common method is quantitative polymerase chain reaction (qPCR) which measures the amount of mRNA in a sample. This method uses specific primers to amplify the mRNA of interest and then quantifies the amplified product using a fluorescent probe. Another method is RNA sequencing (RNA-seq) which involves sequencing the entire transcriptome of a cell and then analyzing the data to determine the abundance of specific mRNA molecules.
Additionally, microarray analysis can be used to measure the relative amounts of different mRNA molecules in a sample. This technique involves hybridizing labeled cDNA to a microarray chip that contains probes for thousands of genes. The fluorescence intensity of the probes is then measured and used to estimate the abundance of specific mRNA molecules.