AS & A Levels: Chromosomes part 1

A living organisms grow and reproduce. since organism

The nucleus contains chromosomes

Before a eukaryotic cell divides, a number of thread like structures called chromosomes gradually 

become visible in the nucleus. They are easily seen, because stain intensely with particular stains. they were originally termed chromosomes, because 'chromo' means colored and 'some' means body.

The number of chromosomes is characteristic of the species. such as, in human cells there are 46 chromosomes, and in fruit fly there are only 8 chromosomes.

• There are matching pairs of chromosomes called homologous pairs. Each pair is given a number.
• Human chromosome is 46 which means 23 from the father and 23 from the mother
• Sex chromosomes, which determine the sex of the individual. All other chromosomes are called autosomes.
• The pairs of chromosomes can be distinguished not only by size and shape, but because each pair has a distinctive banding pattern when stained with certain, as











Set of chromosomes in human  (Karyogram)