Question

Amoeba Sisters Video Recap: DNA Replication

Answer 1

Before starting the explanation in the amoeba sister video, they explain what DNA replication is. We can say that DNA, which in eukaryotic cells is located in the nucleus, contains all the genetic information of a being and its duplication process is important for cell growth, reproduction and repair.

What is DNA replication?

A DNA molecule is made up of two strands that complement each other. For example, if we have an F and an F' strand, in the replication process the strands separate and are used as templates for the formation of complementary strands. Thus, the nucleotide sequence of F determines the sequence of a new F' strand, and F' indicates the composition of a new F strand.

DNA replication process

In the video of the amoebas sisters it is briefly explained that..

1. DNA replication occurs in the 5' → 3' direction and the strands are separated by the action of enzymes, which break the bonds between the nitrogenous bases and unwind the strands, opening the double helix.
2. As DNA uncoiling takes place, other enzymes act to catalyze the synthesis of two new sequences using the parent strands as a template. Each strand created joins an original strand of DNA. Therefore, the process is classified as semi-conservative.
3. DNA is a double helix molecule and for its duplication to occur, the first step is to unpack this structure by the action of the DNA helicase enzyme. The helicase recognizes the origin of replication and works by breaking the hydrogen bonds in the nitrogenous bases A-T and C-G. This process occurs at several points and forms "replication bubbles".
4. As the bonds unravel, it's like a zipper opening, so this step gives rise to a Y-shaped structure called the replication fork, the starting point of duplication.
5. The primase enzyme is responsible for synthesizing a portion of RNA, called a primer. In this step, several primers are generated and are joined to the chain to start DNA synthesis.
6. The DNA polymerase enzyme is the replication enzyme responsible for extending the new strand by adding the bases (A, C, G and T). This step is directed from the 5' end, with a phosphate group, to the 3' end, with a hydroxyl group. This phase is called continuous replication.
7. Among the primers attached to the original strand, several pieces of DNA are attached and are called Okazaki fragments. As the sections will need to be joined later, this phase is called delayed.
8. The exonuclease enzyme is responsible for removing the primers from the original strands after the formation of continuous and discontinuous strands. To avoid sequencing errors, a review and, if necessary, a correction is performed by another exonuclease.
9. The enzyme DNA ligase causes the DNA fragments to be joined and the DNA sequenced into two continuous strands.

thus, in a simple way, how DNA replication occurs in the video of the amoebas sisters.

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