Describe the changes in the structure of the chromosomes during DNA replication.
Question
Describe the changes in the structure of the chromosomes during DNA replication.
Solution
During DNA replication, the structure of the chromosomes undergoes several changes:
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Unwinding: The first step in DNA replication involves the unwinding of the double helix structure of the DNA molecule. This is facilitated by an enzyme known as DNA helicase, which breaks the hydrogen bonds between the base pairs of the DNA strands.
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Replication Forks: The unwinding of the DNA molecule creates a 'Y' shaped structure known as the replication fork. This is the area where the DNA replication takes place.
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Primer Binding: The next step involves the binding of a short RNA primer to the single-stranded DNA. This is facilitated by an enzyme known as primase. The primer serves as the starting point for the new DNA strand.
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Elongation: The enzyme DNA polymerase then adds new nucleotides to the primer, based on the sequence of the template strand. This process continues until the entire DNA molecule is replicated.
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Termination: Once the entire DNA molecule is replicated, the RNA primers are removed and replaced with DNA. The new DNA strands then rewind into the double helix structure, resulting in two identical copies of the original DNA molecule.
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Proofreading: The DNA polymerase also has a proofreading function. It checks the newly synthesized DNA for errors and corrects them. This ensures the accuracy of DNA replication.
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Chromosome Condensation: After replication, the DNA is packaged into chromosomes. This involves the condensation of the DNA into a compact, organized structure. This is facilitated by proteins known as histones, which the DNA wraps around to form a structure known as a nucleosome. The nucleosomes are then further packed into a dense structure to form the chromosomes.
These changes in the structure of the chromosomes ensure that the genetic information is accurately copied and passed on to the next generation of cells.
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