What are the four bases in DNA?
Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), or thymine (T).
Which of these is are pyrimidines ?\?
While thymine, cytosine, and uracil are all pyrimidines, only thymine and cytosine are found in DNA. Uracil replaces thymine in RNA. Adenine is a purine, and is found in both DNA and RNA.
What are the three main components nucleotides?
Nucleotide A nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base. The bases used in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T).
How are 2 nucleotides linked together?
Nucleotides are joined together by covalent bonds between the phosphate group of one nucleotide and the third carbon atom of the pentose sugar in the next nucleotide. This produces an alternating backbone of sugar – phosphate – sugar – phosphate all along the polynucleotide chain.
What is the role of DNA polymerase 3?
DNA Polymerase III, Bacterial DNA polymerase III holoenzyme (Pol III HE) is an enzyme that catalyzes elongation of DNA chains during bacterial chromosomal DNA replication. Together with a DNA helicase and a primase, Pol III HE participates in the replicative apparatus that acts at the replication fork.
Does DNA polymerase 3 need a primer?
Thus, DNA polymerases are template-directed enzymes. DNA polymerases add nucleotides to the 3′ end of a polynucleotide chain. To initiate this reaction, DNA polymerases require a primer with a free 3′-hydroxyl group already base-paired to the template.
Why is DNA polymerase 3 used in prokaryotes?
In prokaryotes, three main types of polymerases are known: DNA pol I, DNA pol II, and DNA pol III. DNA pol III is the enzyme required for DNA synthesis; DNA pol I and DNA pol II are primarily required for repair. There are specific nucleotide sequences called origins of replication where replication begins.
What do DNA polymerase 1 and 3 do?
DNA polymerase 3 is essential for the replication of the leading and the lagging strands whereas DNA polymerase 1 is essential for removing of the RNA primers from the fragments and replacing it with the required nucleotides. These enzymes cannot replace each other as both have different functions to be performed.
What is the function of DNA polymerase I in prokaryotes?
DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. The physiological function of Pol I is mainly to repair any damage with DNA, but it also serves to connect Okazaki fragments by deleting RNA primers and replacing the strand with DNA.