Final answer:
A Holliday junction is a branched nucleic acid structure important in genetic recombination and DSB repair. DNA has a double helical structure with a sugar-phosphate backbone. Nitrogenous base pairs connected across the two strands hold the genetic code.
Step-by-step explanation:
A branched nucleic acid structure that contains four double-stranded arms joined together, which are key intermediates in many types of genetic recombination, as well as double-strand break (DSB) repair, is known as a Holliday junction. This structure is integral in the process of genetic diversity through homologous recombination, as well as in the repair mechanisms that maintain the integrity of the DNA.
The DNA molecule itself is constructed from two long strands that form a double helix, with each strand having a sugar-phosphate backbone. These backbones are comprised of a repeating alternating sugar-phosphate structure, which is formed due to phosphodiester bonds between the sugar of one nucleotide and the phosphate group of another. These sugar and phosphate groups act like the sides of a ladder while the nitrogenous bases (adenine, thymine, cytosine, and guanine) are the rungs, attached to each sugar molecule and paired with their complement across the two strands.
DNA holds the genetic code that instructs cells on protein synthesis. The sequence of nitrogenous bases within the DNA code for genes, which are the functional units of heredity. DNA is essential for the inheritance of genetic traits, and repairing DNA is crucial for the survival of cells.