DNA Replication process is used for producing two similar replicas of the original DNA molecule during cell division. This procedure is defined as a mechanism for transmission of genetic information after generation. The process is followed by numerous steps that involve multiple proteins called replication enzymes and RNA. It is carried out by an enzyme called helicase which breaks the hydrogen bonds holding the complementary bases of DNA together. DNA is made up of two complementary strands and during replication these strands get separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart. The DNA found within the nucleus must be replicated to ensure that each new cell receives an appropriate number of chromosomes.
Steps for the replication of DNA include:
• Initiation: The DNA molecule unwinds and separates to form a small open complex.
• Elongation: RNA polymerase moves along the template strand, synthesising an mRNA molecule
• Termination: In prokaryotes there are two ways in which transcription is terminated.
When a cell divides, each daughter cell receives its full complement of genetic material in the form of chromosomes that contains DNA. A chromosome is made of two long strands of DNA and several types of proteins. A DNA strand is made up of a long backbone of sugar and phosphate units. In DNA, the bases of one strand bind with those of the other strand. The process of replication begins at origin of replication on the double helix known as ‘oriC’. The separation of two strands creates a Y shape, which is known as replication fork. These two replication forks together make structure called replication bubble.
DNA polymerases add nucleotides to 3′ end of an existing DNA strand and the direction of replication is from 5′ to 3′ direction as DNA polymerase acts on the 3′-OH of the existing strand to add free nucleotides.
These two separate strand acts as a template for making new strand of DNA. One strand oriented towards replication fork is known as leading strand and the other moving away from the fork is known as lagging strand.
The lagging strand made in fragments and these small fragments are called as Okazaki fragments. DNA ligase joins together the Okazaki fragments into a single DNA molecule.
The newly synthesised strand of DNA (daughter stand) is made by the addition of a nucleotide that is complementary to the parent strand of DNA.In DNA replication process, one parent strand is always passed on to the daughter helix of DNA.
After elongation of DNA strands, the strands are further checked for errors and repairs, and telomere sequences are further added to the ends of the DNA.
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