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Biology

BIOLOGY OF HEREDITARY AND VARIATION

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

Biology

STRUCTURE OF DNA

STRUCTURE OF DNA What is structure of DNA? The structure of DNA was first explained in 1953 by Watson and Crick. DNA was shown to be a double helix that coils around itself. The two strands are parallel and the distance between the two is constant.   Components of DNA What are the components of DNA?  DNA is made up of repeating units called nucleotides. Each nucleotide is composed of: A five-carbon sugar (deoxyribose). Phosphate molecule. Nitrogenous base, four types are available i.e. Adenine – (A) Guanine – (G) Cytosine – (C) Thymine – (T) The bases are represented by their initials as A, G, C and T respectively. The sugar alternates with the phosphate, and the two form the backbone of the strands. The bases combine in a specific manner, such that Adenine pairs with Thymine and Guanine pairs with Cytosine. The bases are held together by hydrogen bonds.… Read More »STRUCTURE OF DNA

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