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BIOLOGY OF HEREDITARY AND VARIATION (GENETICS)   DEFINITIONS OF GENETIC TERMS What is Genetics? Genetics is the scientific study of heredity and variation in all living things. The word genetics was coined by Dilliam Bateson (1906). What is hereditary?: Hereditary/Inheritance is the transmission and expression of characters or traits from parents to offspring. It accounts for the usual resemblance between a parent and its offspring. What is Variation? Variation is the differences which exist between parents and offspring and among the offspring.   What is Genes? Genes are hereditary or basic units of inheritance located in chromosomes and responsible for the transmission of characters from parents to offspring. The hereditary units were named genes by Johannsen in 1909. What are Chromosomes? Chromosomes are rod or thread like bodies found in the nucleus of a cell which house the genes. What are Characters? Characters are inheritable features possessed by an organism e.g… Read More »BIOLOGY OF HEREDITARY AND VARIATION



STRUCTURE. FUNCTIONS AND PROPERTIES OF CHROMOSOMES What are chromosomes? These are thread-like structures found in the nucleus. They are normally very thin and coiled and are not easily visible unless the cell is dividing. When a cell is about to divide, the chromosomes uncoil and thicken. Their structure, number and behaviour is clearly observed during the process of cell division. The number of chromosomes is the same in all the body cells of an organism.In the body cells, the chromosomes are found in pairs. Each pair is made up of two identical chromosomes that make up a homologous pair. However sex chromosomes in human male are an exception in that the Y-chromosome is smaller.   Number of Chromosomes Diploid Number (2n) This is the number of chromosomes found in somatic cells. For example, in human 2n = 46 or 22 pairs (44 chromosomes) are known as autosomes (body chromosomes”) While… Read More »CHROMOSOMES – STRUCTURE, FUNCTIONS AND PROPERTIES

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