Answer
A gene is a specific sequence of DNA bases or nucleotides that specify a particular protein or trait. It is the unit of heredity.
The process of gene expression includes the following steps: first transcription; this is the copying of gene sequence from DNA to mRNA.; this is followed by translation which is the reading of the mRNA code by rRNA and tRNA in the ribosome; mRNA is bound to the ribosome, and as the code is read appropriate amino acids are brought in and assembled to form the specified polypeptide. The assembly of this polypeptide or protein is the primary chemical expression of the gene. Proteins thus formed control structural and physiological characteristics of cells, tissues and organisms. This is the ultimate meaning of gene expression
Work Step by Step
Gene expression is the process by which a gene or genetic code dictates the appearance or development of the phenotypic characteristic , for example abnormal hemoglobins in sickle cell anemia or Beta -Thalassemia. The phenotype itself can also be considered the expression of the gene; so "gene expression" can be thought both as a process and as an perceptible physical or biochemical characteristic.
