Human Genetic Code and Human Chromosomes:

Chromosomes as discussed previously are the lengths of DNA grouped together, between 5000 and 50,000 genes per Chromosome. Not only do the genes between species vary, but the number and length of chromosomes. For instance a garden pea for instance has 14 chromosomes, a potato 48 and a crayfish 200.

Human Genetic Code and Human Chromosomes: There are 46 chromosomes in the living cell of a human being and these chromosomes carry the genetic information that decides how a person will grow- whether he or she will be dark or fair, short or tall, blue-eyed or brown. But the sex cells, the female egg and the male sperm each have only 23 chromosomes. They fuse at conception to make a cell containing 46 chromosomes, half from each partner and it is this mixing of two sets of characteristics that creates the diversity of human life. Thus, Chromosomes are often spoken of as 23 pairs. The major difference between humans are the 23rd chromosomes - X and y. The Chromosome X is much larger and has more genetic information than the smaller y chromosome. o women have 2 X chromosomes and 0y chromosomes, while o men have 1X and 1y chromosome. However, sperm produced by men can be of two types, X or y. In terms of bases, the entire DNA code of the human being is around 3 Billion, or 3 gigabytes of memory potential for chemical triple-base code. However up to 85% of the entire DNA code appears to code chemical material, the rest is currently classed as "junk DNA' by the experts in this field. This non-coding material is found throughout the code for functioning and redundant genes as well as on its own. It is also estimated that only around 5% of all DNA of a human being is functioning, the rest (10%) being redundant genes. There is estimated to be 100,000 genes in the genetic pool for humans. Estimated percentage of Human DNA coding genes If the DNA contained in the 46 human chromosomes were laid out end to end it would stretch several metres in length. Thus there is a very large amount of genetic detail embedded in these very long DNA strands, yet they are folded and compacted into the tiny space of the cell nucleus, which is only a few microns in diameter

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Deoxyribonucleic acid (DNA)

Deoxyribonucleic acid (DNA) is the basic genetic material of most living organisms. Although a large and apparently complex molecule, the structure of DNA is in fact astonishingly simple. A single DNA molecule consists of two separate strands wound around each other to form a double-helical (spiral) structure. Each strand is made up of a combination of just four chemical components known as nucleotides- all of which have the same basic composition. Each nucleotide consists of a sugar molecule (deoxyribose) linked to a phosphate group to form the helical backbone; different nucleotides are distinguished only by the identity of the nitrogen-based unit called the nucleotide base bonded to the sugar molecule.

The four bases are:

(A) adenine (C) cytosine (G) guanine (T thymine

The bases lie in the central region of the double helix, with each base linked by hydrogen bonds to specific complementary base on the partner strand. The base pair rule states that wherever you have an A on one strand, there will be a T at the same relative position on the other strand; wherever you have a G on one strand, you will have a C on the other strand. In addition, the number of molecules of A in a sample always equals the number of molecules of T. Similarly, the number of C molecules always equals the number of molecules of G. DNA is therefore basically a linear information macro molecules much like the long strips of computer tape used in the first computers. A typical DNA base sequence might be: 5'-AGCTTATTGCATAAGCGCGAT-3' 5' and 3' These refer to the left-hand and the right-hand ends respectively of a DNA or RNA base sequence.

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