Describe the Biochemical Composition Structure and Replication of Dna Essay

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Background DNA is an abbreviation for deoxyribonucleic acid, but it is usually known by its initials alone. DNA is found in practically all living organisms, and it is now known to carry genetic information from one cell to the next, and from one generation to the next. The units of inheritance, called genes, are actually sections of the DNA molecule. Nuclei of the cells of higher organisms contain thread-like bodies called chromosomes, which consist of DNA, wrapped around proteins. So understanding how the DNA molecule behaves inside cells helps explain how genetics works at the simplest level. In the nucleus of every normal cell of the human body there is over 1 metre of DNA, divided between 46 chromosomes. DNA is a…show more content…
Sexual reproduction and meiosis DNA also replicates reliably in the process of meiosis, which happens before sex cells ( gametes ) are produced, but only half the normal number of chromosomes (and hence genes, and DNA) are distributed to each gamete. The sharing process in halving the number of chromosomes also includes elements of "scrambling" which introduce variation, so each gamete has a unique DNA content. Meiosis | | | | | | Firstly, chromosomes associate with their "partners", then each replicates, perhaps with exchange of genetic material. Secondly, chromatids separate - as in mitosis. | | | | In meiosis, the nucleus divides twice to produce 4 nuclei, which then form into 4 genetically different sex cells (gametes), each containing half the number of chromosomes of the original cell (23 in human cells) Therefore every organism produced as a result of sexual reproduction varies. However, the DNA built into the nucleus of a gamete may also be changed due to a random event called a mutation, which may alter or even prevent the normal activity of a gene inside cells. In this way a different form of the gene, called an allele , is produced, and will possibly be passed on to the next generation. Because each chromosome usually has a partner in the nucleus, the effect of a mutant allele may be hidden by the DNA of a normal allele of that gene which produces a normal characteristic. This is the basis of

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