Chromosome are thread like structure that appears inside the nucleus at the time of cell division.They were first observed by German embryologist Walther Fleming in 1882,when he was examining the rapidly division cell of Salamander Larvae.Since there discovery chromosomes have been found in cell of all eukaryotes.There number varies however from species to species.Penicilium,a fungus,has only one pair of chromosomes while some ferns have more than 50 pairs.A mosquito has 6 honeybee 32,corn20,sugarcane 80,frog 26 and a mouse has 40 chromsomes. Human cells have 46 chromosomes. Consist of 23 pairs.Each of these 46 chromosomes contain hundred or thousand of genes that play important rules in determining how a person body develop the functions.
The possessions of all these chromosomes is therefore, essential for survival.Missing of a part or whole of chromosomes leads to serious consequences,usually death occurs.
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| CHROMOSOMES |
TYPES OF COLONING:
Typically a chromosomes is made of chromatids ,centromere , (primary constriction) and a secondary constriction.
Chromosomes may widely differ in apperance. They vary in size staining properties, the location of centromere,the relative length of two arms on either side of centromere, and the position of constricted regions along the arms.The particular ray of chromosomes that an individual possesses is called its karyotype. Karyotype show marked difference species and sometimes even among individuals of the same species.
The chromosomes are called telocentric, acrocentric,sub metacentric and metacentric depend upon the location of centromere between the middle and tip of chromosomes.
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