 |
| Genetic Material |
|
| The genetic material is a nucleoprotein called chromatin. It is made up of DNA and protein. |
| |
|
| It is a double stranded molecule with each strand being made up of many nucleotide units. Each nucleotide is made up of a nitrogenous base, a sugar molecule and a phosphoric acid molecule. |
| |
| Nitrogenous bases are of two kinds: |
| |
 purines |
| |
|
pyrimidines |
| |
| The nitrogenous bases present in DNA are adenine and guanine, which are purines and cytosine and thymine, which are pyrimidines. |
| |
| The sugar molecule present in DNA is deoxyribose. The nitrogenous base, sugar and phosphoric acid together join to form a nucleotide that looks like this: |
| |
 |
| |
| Formation of a Nucleotide |
| |
| Many nucleotides join to form the polynucleotide chain. |
| |
 |
| |
| Formation of Polynucleotide |
| |
| Each DNA molecule has two such polynucleotide chains joined to each other by hydrogen bonds. The hydrogen bonds are between the nitrogenous bases of the opposite nucleotides. |
| |
 |
| |
| If the polynucleotide chains are the sides of the ladder, the bonds can be compared to the rungs of the ladder. The whole molecule can be likened to a rope ladder twisted around to from a helical structure. The DNA molecule is twisted around a core of proteins. |
| |
| Short chains of the DNA form the genes. Each gene is, therefore, a series of nucleotides in a particular sequence. Each gene codes for a particular trait. The genes are arranged in a linear manner on the chromosomes. |
| |
|
| |
| The complimentary property of the nucleotides of DNA has been proved to be the most powerful tool of genetic engineering. After cutting a segment of DNA or gene with the help of specific enzyme, it can be joined or attached with the DNA of a different organism. Such type of organism that contains a segment of foreign DNA or gene, is known as transgenic organism, or genetically modified organism (GMO). |
| |
