Question

*minimum 250 words

You might find it amazing that most cells in the human body each contain at least one entire copy of your genome!!! That means a single cell has the genetic "blueprint" for your ENTIRE body! However, a particular cell does not "express" every gene found in your genome. How would you define "gene expression" in your own words?"

Answer 1

A DNA molecule isn't just a long, boring string of nucleotides. Instead, it's divided up into functional units called genes. Each gene provides instructions for a functional product, that is, a molecule needed to perform a job in the cell. In many cases, the functional product of a gene is a protein.

Many genes provide instructions for building polypeptides. The construction of a polypeptide involves two major steps: transcription and translation.

• In transcription, the DNA sequence of a gene is copied to make an RNA molecule. This step is called transcription because it involves rewriting, or transcribing, the DNA sequence in a similar RNA "alphabet." In eukaryotes, the RNA molecule must undergo processing to become a mature messenger RNA (mRNA).

• In translation, the sequence of the mRNA is decoded to specify the amino acid sequence of a polypeptide. The name translation reflects that the nucleotide sequence of the mRNA sequence must be translated into the completely different "language" of amino acids.

During expression of a protein-coding gene, information flows from DNA→RNA→protein. This directional flow of information is known as the central dogma of molecular biology. Non-protein-coding genes (genes that specify functional RNAs) are still transcribed to produce an RNA, but this RNA is not translated into a polypeptide. For either type of gene, the process of going from DNA to a functional product is known as gene expression.