describe how two nucleotides are linked to form a single strand of dna in order for the strand to have 5 prime to 3 prime orientation
In DNA, nucleotides are linked by a phosphodiester bond which forms between the phosphate group of one nucleotide and the sugar group of the next nucleotide. The sugar group in DNA is a deoxyribose molecule, which contains a 3' hydroxyl (-OH) group and a 5' phosphate group (-PO4).
To form a single strand of DNA with a 5' to 3' orientation, the 5' phosphate group of one nucleotide must be linked to the 3' hydroxyl group of the next nucleotide. This linkage occurs through a condensation reaction, which involves the removal of a water molecule (-H2O) from the two nucleotide subunits, resulting in the formation of a phosphodiester bond between them.
Specifically, the 3' hydroxyl group of the sugar in the first nucleotide (the 5' end) will react with the phosphate group of the second nucleotide, resulting in a covalent bond between the 3' carbon of the first nucleotide and the 5' carbon of the second nucleotide. This process is repeated for each successive nucleotide, resulting in a long chain of nucleotides linked by phosphodiester bonds. The resulting DNA strand will have a 5' end with an available phosphate group and a 3' end with an available hydroxyl group, determining its 5' to 3' orientation.
To form a single strand of DNA with a 5' to 3' orientation, two nucleotides are linked through a process called phosphodiester bond formation. Here is a step-by-step description:
1. Nucleotides: The basic building blocks of DNA are nucleotides, which consist of three components: a nitrogenous base, a sugar molecule (deoxyribose), and a phosphate group.
2. Sugar-Phosphate Backbone: The sugar molecule in each nucleotide is connected to a phosphate group via a phosphodiester bond. This bond attaches the 5' carbon of one sugar molecule to the 3' carbon of the adjacent sugar molecule.
3. Hydroxyl Group: The phosphate group attached to the 5' carbon of one nucleotide has two oxygen atoms, one bonded to the phosphate and the other with a free hydroxyl group (OH). This free hydroxyl group is referred to as the 3' end of the nucleotide.
4. Dehydration Synthesis: The formation of a phosphodiester bond occurs through dehydration synthesis. During this process, the hydroxyl group at the 3' end of one nucleotide reacts with the phosphate group of another nucleotide, resulting in the release of a water molecule.
5. Polymerization: This process is repeated as more nucleotides are added to the growing DNA strand. Each new nucleotide is linked to the previous one through a phosphodiester bond, extending the sugar-phosphate backbone.
6. 5' to 3' Orientation: The 5' to 3' orientation refers to the numbering of the carbon atoms in the sugar molecules of the DNA backbone. The 5' carbon is attached to the phosphate group, while the 3' carbon has a free hydroxyl group. This orientation is essential in DNA replication and transcription processes.
By repeating these steps, nucleotide by nucleotide, a DNA strand is formed with a 5' to 3' orientation. It is important to note that in a double-stranded DNA molecule, the two strands run in opposite directions: one strand with a 5' to 3' orientation and the other with a 3' to 5' orientation. This arrangement is known as antiparallel.