the discovery of dna structure

DNA molecule is a double helical structure made of deoxyribo nucleotides. RNA is also present in nucleus as well as cytoplasm. DNA is the major source of genetic information which is copied into RNA molecules (transcription). The sequence of nucleotides contains the '..

The most significant feature of DNA molecule is its capacity to make its own identical copies. This property is called replication. It occurs regularly during the synthetic phase of the cell cycle, every time a cell divides. During replication, the DNA molecule unwinds itself fr..

Discovery of the Cell - The history of the discovery of cells dates back to the 17 t h century and is closely associated with the history of the invention of microscopes. An Italian microscopist Marcello Malpighi studied the structure of some plants and proposed the id..

The DNA double helix structure is similar to a twisted ladde..

Double helical structure exists in six different forms. They are A-DNA, B-DNA, C-DNA, D-DNA, E-DNA and Z-DNA. Among these only 3 forms of DNA are important. They are B-DNA, A-DNA and Z-DNA..

Deoxyribose Nucleic Acid (DNA) - With the exception of a few viruses, DNA forms the genetic material in all living organisms. In the prokaryotic cells DNA occurs in the cytoplasm. In the eukaryotic cells it is confined largely to the nucleus and forms the main componen..

Mechanism of DNA Replication - It is a complex process and involves the participation of over a dozen enzymes and other protein factors. The intertwined DNA starts separating from a particular point and this is known as the origin of replication. The second step is that the two ..

DNA is a double stranded molecule (double helix) 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. Each DNA molecule has two such polynucleotide chains joined to each other..

RNA molecule is a single stranded structure made of ribonueleotides. RNA contains the pyrimidine uracil instead of thymine in DNA. RNA is of 3 types, based on the cellular compositio..

fig. 19.3 Structure of Chromosomes The terminal end of a chromosome is called as telomere. It is functionally different from the rest of the chromosome. A chromatid may breakup into pieces and the pieces may rejoin, but no segment becomes connected to the telomere. Thus, the telomere show..