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DNA replication is the process by which a cell duplicates its DNA to produce two identical copies. It occurs during the S phase of the cell cycle. The process begins with the unwinding of the double helix structure of DNA by the enzyme helicase. This creates two separate strands, known as the template strands.
Next, an enzyme called DNA polymerase attaches to the template strands and starts adding complementary nucleotides to each strand. Adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). This results in the formation of two new strands, each complementary to the original template strands. This process continues until the entire DNA molecule is replicated.
Transcription is the process by which the information encoded in DNA is copied into a complementary RNA molecule. It occurs in the nucleus of eukaryotic cells. The process begins with the unwinding of the DNA double helix by RNA polymerase. The enzyme then attaches to the DNA template strand and starts synthesizing a complementary RNA molecule.
Unlike DNA replication, transcription only copies a specific region of the DNA molecule, known as a gene. The RNA molecule, known as messenger RNA (mRNA), is synthesized in the 5' to 3' direction, complementary to the DNA template strand. Adenine (A) pairs with uracil (U) in RNA, instead of thymine (T).
Once the mRNA molecule is synthesized, it undergoes post-transcriptional modifications, such as the addition of a 5' cap and a poly-A tail. These modifications protect the mRNA molecule and facilitate its transport out of the nucleus and into the cytoplasm.
Translation is the process by which the information encoded in mRNA is used to synthesize a protein. It occurs in the cytoplasm of both prokaryotic and eukaryotic cells. The process involves the participation of ribosomes, transfer RNA (tRNA), and amino acids.
The mRNA molecule binds to a ribosome, which serves as the site of protein synthesis. The ribosome reads the mRNA molecule in groups of three nucleotides, known as codons. Each codon corresponds to a specific amino acid.
tRNA molecules, each carrying a specific amino acid, bind to the ribosome and bring the corresponding amino acid to the growing polypeptide chain. The tRNA molecules have an anticodon that is complementary to the codon on the mRNA molecule.
As the ribosome moves along the mRNA molecule, it catalyzes the formation of peptide bonds between the amino acids, resulting in the synthesis of a polypeptide chain. This process continues until a stop codon is reached, signaling the end of protein synthesis.
In summary, DNA replication involves the duplication of the DNA molecule, transcription copies the DNA information into mRNA, and translation uses the mRNA to synthesize a protein. These processes are essential for the proper functioning and growth of cells.