DNA molecule composition and the functions of genes

What are the gens ?

They are the parts of DNA present on the chromosomes and they control the individual’s hereditary traits , And the hereditary traits are transferred from the parents to their offspring through the hereditary factors which are known as Genes .

You should know that the cell nucleus contains a number of chromosomes , and each chromosome consists of two chromatids , Each chromatid chemically consists of proteins and DNA ( a nucleic acid ) which carries the hereditary traits of the living organism .

DNA molecule composition

The gene is the building block of nucleic acid ( DNA ) , The gene consists of more smaller blocks ( consecutive units ) called nucleotides , Each nucleotide consists of three components which are a phosphate group , a deoxyribose sugar ( 5 – carbon sugar ) and a nitrogenous base .

There are four types of nitrogenous bases like Adenine ( A ) , Thymine ( T ) , Cytosine ( C ) , and Guanine ( G )Scientists Watson and Creek were able to make a model of the DNA molecule .

DNA molecule

DNA molecule

DNA molecule is composed of two strands coiled around each other like the spiral ladder called the double helix , where the sides of this consist of sugar molecules ( Deoxyribose sugar ) and phosphate groups , Its steps consist of groups of the nitrogenous bases , where , The adenine pairs with Thymine ( A = T ) , The Guanine pairs with Cytosine ( G ≡ C ) .

How do you inherit your genes ?

It is very important to know that the individual inherits half of his genes from the father , and the the other half from the mother and  as follows :

By the meiosis division , The reproductive cells produce the male gametes ( the sperms ) containing half number of the chromosomes ( n ) , Female gametes ( ova ) containing half number of chromosomes ( n ) .

After the fertilization , a zygote ( containing 2n of chromosomes ) is found and it is divided mitotically many successive divisions to form the cells , Each cell in the fetus ‘s body carries a complete set of genes responsible for the appearance of the hereditary traits .

The cells group together forming the tissues which form the organs until all the body of the fetus is formed .

How do the genes perform their functions ?

Badel and Tatum the scientists ( who took Nobel prize in the year 1958 ) discovered the means of how the genes controls the appearance of a trait , where they found that every gene gives a special enzyme .

This enzyme is responsible for the occurrence of a chemical reaction , Each chemical reaction resulting in a protein shows a specific hereditary trait .

The function of genes 

The genes control the body growth , the features and the functions , They are responsible for the hereditary traits appearance as the hair colour , the eye colour , ………… and so on .

The inheritance of the trait of eye colour

If you inherit one gene from one of your parents which is responsible for the brown coloured eyes trait ( Dominant trait ) , The gene is working on the enzyme formation which is responsible for the occurrence of the chemical reaction producing the protein that makes the trait of the brown eye appears on you .

The Danish scientist Johansen used the term gene instead of the hereditary factor and he introduced the term the genotype for the gene structure in the living organism , and the term phenotype for the hereditary trait that appear on the living organism .

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