Entries Tagged 'DNA' ↓

Palindromic sequence: A nucleotide sequence which is the same when read in either direction DNA locus whose 5` to 3` sequence is identical on each DNA strand. The sequence is the same when one strand is read left to right and the other strand is read R to L.

What Is Transcription:Transcription is a process in which ribonucleic acid is synthesized from DNA. The word gene refers to the functional unit of DNA that can be transcribed. Thus the genetic information stored in DNA is expressed through RNA – for this purpose, one of the two stands of DNA serves as a template and produces working copies of RNA molecules. The other DNA strands which does not participate in transcriptions is referred to  as coding stands or antisense strand. The entire molecule of DNA is not expressed in transcription. RNAs are synthesized only for same selected regions of DNA. The exact reason for the selective transcription is not known. The product form in transcription is referred to as primary transcript.

A single enzymes DNA dependent RNA polymerase or simply RNA polymerase. Synthesizes all the RNAs in prokaryotes. RNA polymerase of E.Coli is a complex holo enzyme with five polypeptide subunits 1a,1b,1b` and one sigma (0) factor. The enzyme without sigma factor is referred to as core enzyme (a2bb`) Continue reading →

Nucleosomes:Any of the repeating subunits of chromatin in eukaryotic cells , consisting of a DNA chain coiled around a core of histones. The structure is responsible in part for the compactness of a chromosome

Watson and Crick: The double helical structure of DNA was proposed by james Watson and francis crick in 1953. The structure of DNA double helix is comparable to a twisted ladder. The salient features of Watson – crick model of DNA are given below. Continue reading →

Nucleoside :A nucleoside is a compound in which a purine or pyrimidine base is bound via a N-atom to C-1 replacing the hydroxyl groups of either 2-deoxy-d- ribose or of D- ribose but without any phosphate groups. The common nucleosides in biological systems are adenosine guanosine, cytidine, and widine and deoxyaclenosine, deoxyguanosine, deoxycytidine and thymidine