The unit of heredity transmitted from one generation to the next generation is called a gene. A gene represented the heredity unit which responsible for inheritance of genetic characters of sex organism. The term gene was coiled by Danish Gene tieist wilhelm Johannsen in 1909.Genes (so called factors) transmit individual traits(called characters according to Handel)
Based on the classical concept, the gene is regarded as
The unit of junction. According to this definition gene are consider as the unit of
chromosome responsible for the expression of a trait.
Example:- blue or brown
eyes in humans.
The unit of mutation. According to this elefination gene and the smallest segment of chromosomes capable of undergoing mutation
The enzymes, protein factor and metal ions required for this pressure are:-
It is an enzyme which breaks the hydrogen bond and separates the DNA strands. Thus, a fork is formed of the junction known as replication fork.
These are the molecules which attached tightly to the exposed single stranded DNA in order to stabilize the single stranded DNA long enough for replication.
It is an enzyme responsible for synthesis of short RNA primers. A RNA primer a small strand of RNA which guides the process of replication.
It is an enzyme responsible for catalyzing the synthesis of DNA
It an enzyme responsible for causing nick in the DNA.(Nick means cutting or breaking of phosphodiester bond)
It is an enzyme which digest the RNA primers after the DNA synthesis is over.
It is an enzyme which seals the gap in the synthesized DNA fragments
The four deoxyribonucleoside triphosphate (dNTPs) such as dATPs, dGTPs, dTTPs.
It is an essential requirement for the synthetics of nitrogenous base.
These ions are essential for DNA synthesis
The Mechanism of DNA replication is a complex phenomenon which involve the following steps:
DNA is a long chain of polynucleotides. It has many replication units called replicons. Replication is iniated at each replicon by producing a nick (cut) in one of the strands of a specific initiation point called (ori-site). The nick is produced by an enzyme called Endonuclease
Free nucleotides present in the nuclei plasm as deoxyribonucleotides monophosphates (DNHPS) -dAMPS, dGMPs dCMPS, and dTMDs are activated into triphosphates (dAMPS, dGTPTs, dCTPs, dTTPs) with the help of an enzyme phosphorylase in the presence of ATP. This process is known as phosphorylation.
The unwind of two DNA strands in the presence of an enzyme helicase, which breaks the hydrogen bonds between the nucleotides. Due to the unwinding of two DNA strands, a y-shaped fork called replication fork is formed. Now both separated DNA strands are called templates.
Replication is guided by RNA primer. RNA primer is a small strand of RNA that is synthesized by an enzyme primase. Primase is attached to the template DNA at a site called initiation site from where the DNA synthesis begins.
Replication always initiated from 5' direction to 3' direction.
The replication is terminated when ever two replication forks meet.
Sometimes the wrong bases may be inserted during replication. It is an error. The probability of which error is about once per 100000 nucleotides. The error is connected is by inserting the correct nucleotides. This process is called Proofreading.
The replication in which half of the original DNA is conserved and half is the newly synthesized one is called semi-conservative mode of replication of DNA.
