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Bioscience in brief

An introduction to genes and crops

What is a gene?

Genes are small segments of a long molecule called DNA that is composed of four different nucleotides: adenine (A), thiamine (T), cytosine (C) and guanidine (G). DNA is a double stranded molecule (A always pairs with T, and C with G).

These number and order of the bases spell out the language known as the genetic code, which is universal to all life forms.

The nucleotides in a gene encode a recipe or template to produce a protein; the information in genes is sufficient to produce all the proteins the cells of an organism need.

Genes instruct cells how to function, and what characteristic they should express. For example, in flowers, the blue pigment expressed in petal cells. Gene activity is tightly regulated.

1. Nucleotides in the DNA double helix: adenine (A – red) pairs with thiamine (T –yellow) and  cytosine  (C – blue) with guanidine (G – green)

2. DNA molecule composed of paired nucleotides, and a backbone of sugar and phosphate molecules. The DNA molecule is coiled.

3. Genes, the heritable units of genetic information, are stretches of DNA. The information encoded within the DNA structure of a gene directs the production of proteins.

4. The DNA is further packaged into structures called chromosomes. These also contain proteins, which serve to package the DNA and control its functions.

5. Chromosomes are packaged by proteins into a condensed structure called chromatin. This allows the very long DNA molecules to fit into the cell nucleus.

6. An organisms is made up of thousands of cells, each containing the same genetic information