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Bioscience in brief

What is a gene?

Gene Expression

All the cells in an organism carry the same genetic blueprint, but only selected genes are expressed and translated into proteins in each cell. What genes are expressed and how their products interact makes cells develop and function differently.

Humans have about 210 different cell types, and our body is formed by 50 to 70 trillion cells. Plants have fewer types of cells. Growth and development needs to be coordinated by the selective switching on and off of genes.

Genetic information is read in two stages: first the information coded in the DNA is transmitted to a messenger known as messenger RNA (mRNA). RNA is similar to DNA, but it is a single strand and thiamine (T) is replaced by a different nucleotide: uracil (U). The information in mRNA is translated into a sequence of amino acids that form a protein. The work is done by ribosomes which are the cell’s protein factories. Proteins carry out the information specified in genes, although for some genes the functional product is a RNA molecule.

The process of gene expression is used by all known life forms.