Genetics 2
The diagram attempts to simplify the relationship between the cell nucleus, the chromosome, and the DNA in an animal cell (eukaryote).

The chromosome is a coiled DNA molecule within the cell's nucleus that carries the bees genetic code. Most of the time the chromosome's structure is loose and indistinguishable. Only in the stage of cell division immediately before the cell divides (the metaphase) does the chromosome draw itself into a compact, rod-like structure which can be seen under a microscope after the application of a special dye to the cell which the chromosomes absorb. It is this ability to absorb a coloured dye that gives the chromosome its name, which means "coloured body".

DNA - is the abbreviation for deoxyribonucleic acid. DNA has a characteristic double-helix structure that resembles a gently twisting ladder. The DNA helix does a complete turn for every 10 base pairs. The supporting rails of this structure are deoxyribose, a sugar, attached to a phosphate group. The rungs of the ladder are pairs of nitrogen bases: adenine (A), thymine (T), guanine (G), and cytosine (C).
Complementary Base Pairing: adenine always pairs with thymine; guanine always pairs with cytosine through hydrogen bonding.
More information on the chemical structures of the base pairs can be viewed as a pop-up

A gene is a segment of the DNA (on a specific site on a chromosome - the locus) that is responsible for the physical and inheritable characteristics or phenotype of the bee. It also specifies the structure of a protein, and an RNA molecule.

cell nucleus-chromosome-DNA-gene relationship
image adapted from
Next page: Genetics 3.
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