DNA replication is a semi-conservative process, which creates an identical replica of an already existing DNA double helix sequence. During DNA replication, the two antiparallel DNA strands are split in to the 'leading' and the 'lagging' strand by the enzyme DNA Helicase. This creates an open structure called the replication fork. By seperating the strands, free nucleotides have easy access to bond to the strand through complementary base pairing. The base A (adenine) bonds to T (thymine) and base G (guanine) bonds to C (cytosine) through hydrogen bonding. An enzyme called RNA primer adds a primer to the 3prime end of each strand. A primer is a short sequence of complementary base pairing, to get the whole system running. After this, the replication enzyme DNA Polymerase III can attach free nucleotides to the strands through complementary base pairing. DNA polymerase III moves in a 5prime to 3prime direction. The leading strand of DNA undergoes complementary base pairing smoothly as it runs in the direction from 5prime to 3prime, the same as the direction in which DNA Polymerase III works. However, the lagging strand runs in the opposite direction, from 3prime to 5prime. This means nucleotides can only be added discontinuously. RNA primers have to attach where they can, which is at different parts along the strand, to be able to initiate strand synthesis. This creates small fragments of DNA that have undergone complementary base pairing called okazaki fragments. These can later be linked together by another enzyme called DNA ligase to create a full strand, to complete DNA replication. Show
Delete Content DNA replication of the leading and lagging strand The helicase unzips the double-stranded DNA for replication, making a forked structure. The primase generates short strands of RNA that bind to the single-stranded DNA to initiate DNA synthesis by the DNA polymerase. This enzyme can work only in the 5' to 3' direction, so it replicates the leading strand continuously. Lagging-strand replication is discontinuous, with short Okazaki fragments being formed and later linked together. This image is linked to the following Scitable pages:
The decoding of information in a cell's DNA into proteins begins with a complex interaction of nucleic acids. Learn how this step inside the nucleus leads to protein synthesis in the cytoplasm.
Save NoteThe DNA replication process is generally referred to as discontinuous, because the polymerizing enzyme can add nucleotides only in the 5’-3’ direction, synthesis in one strand(leading strand is continuous in the 5’-3’ direction towards the fork. In
the other strand (lagging strand), as the forks opens, multiple sites of initiation are exposed. The synthesis, then proceed in short segments in the 5’-3’ direction: that is, synthesis in the lagging strand is discontinuous. The short segments of DNA synthesized on the lagging strand are called Okazaki fragment. These fragments are about 1000 – 2000 nucleotide long.
What is a difference between leading and lagging strand synthesis in DNA replication?The leading strand is synthesized in a continuous manner, whereas synthesis of the lagging strand requires a primase that makes RNA primers that are extended by the DNA polymerase to form Okazaki fragments — short DNA fragments that are processed to produce a continuous DNA strand.
What is the difference between the leading strand and the lagging strand in DNA replication quizlet?The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction. The leading strand requires an RNA primer, whereas the lagging strand does not.
What are the leading and lagging strands in DNA replication?During DNA replication, one new strand (the leading strand) is made as a continuous piece. The other (the lagging strand) is made in small pieces. DNA replication requires other enzymes in addition to DNA polymerase, including DNA primase, DNA helicase, DNA ligase, and topoisomerase.
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What is the difference between the leading and lagging strand in DNA replication?
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