All About Biological Sciences

Encompasses the Biological World

CHROMOSOME AND DNA RELATIONSHIP

Life depends on the ability of cells to store, retrieve and translate the genetic instructions required to make and maintain a living organism. The hereditary information is passed on form a cell division and form one generation of an organism to the next through the reproductive cell. These instructions are stored with in every living cell on its genes.Gene: “Gene is information conduction elements that determine the characteristics of a species”.
History: Genetics emerged as a science at the beginnings of the twentieth century, scientist become able to know about the chemical nature of gene.
The information in a gene is copied and transmitted from parent cell to daughter cell millions of time during the life of a multicellular organism and it survives the essentially unchanged.
What kind of instructions does the genetic information contain?

Genetic information consists primarily of  instruction for making proteins .Proteins are the macromolecules , that are involve in cellular  functions .They serve as building blocks for cellular structure and form enzymes.

The crucial advance made in the 1940s was the identification of DNA (that carries genetic information).The mechanism where by the hereditary information is copied for transmission from cell to cell and how proteins are specified by the instruction in DNA remained completely mysterious. In 1953 the mysterious was solved when the structure of DNA was determined by James Watson and Francis Crick. They had recognized that genes are carried on chromosomes which were discovered in 19th century as thread like structures in the nucleus of eukaryotic cell. The chromosome is composed of DNA and histone protein. DNA is the genetic material. It exists with protein in the fix form. The chromosomes shows following phases: Chromatin (highly dispersed state of chromosomes, the chromosomes remains in chromatin state during most of the life cycle of cell. Therefore, the genes actively participate in the formation of protein). Chromosomes (the highly condensed form of chromatin during division of cell, this condensed state distribute chromosomes equally between newly formed cells. They are visible during cell division, biochemical analysis become possible, consist both DNA and protein. Chromosomes function largely to pack and control the enormously large DNA that can fit inside the cell.DNA is a long polymer consists of different nitrogenous basis. These nitrogenous bases are Adenine, Guanine, Cytosine and Thymine. Adenine and Guanine p0osses large molecules and form double ring structures, they are called purines. Cytosine and Thymine possess smaller form singled ringed structures and are included in pyrimidines.These nitrogenous bases are very similar to each other. These nitrogenous bases are bind with each other by covalent and ionic bond.DNA of human contain many genes coding  protein that serve essential functions inside the cell. Human genome contains 2.3×10  DNA nucleotide pairs, with 22 different autosomes and 2 sex chromosomes.
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