What is the structure and function of DNA, and how does it replicate?

Question

DNA (Deoxyribonucleic acid) is a molecule that carries genetic information in all living organisms. It is a long, double-stranded, helical structure that consists of four nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). These nucleotides are joined together by covalent bonds to form a long chain that is twisted into a double helix.

The structure of DNA is made up of two strands of nucleotides that run in opposite directions and are held together by hydrogen bonds between the complementary base pairs. Adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). The sequence of these base pairs determines the genetic code and instructions for the development and function of all living organisms.

The primary function of DNA is to store and transmit genetic information from one generation to the next. This genetic information is carried in the form of genes, which are specific sequences of nucleotides that encode for specific proteins and traits.

DNA replication is the process by which cells make copies of their DNA before cell division. The replication process is initiated by an enzyme called DNA helicase, which unwinds the double helix by breaking the hydrogen bonds between the base pairs. The resulting single-stranded DNA then serves as a template for the synthesis of a new complementary strand by the enzyme DNA polymerase.

Answer 1

That is a great amount of detail for your question. Well done! We could add some more detail depending on what you need to fully answer the question.

DNA Structure: In addition to the base pairs you mentioned, the backbone of DNA is made of a repeating set of phosphates and sugars. The sugar is deoxyribose (which has a very similar structure to ribose) and is the first part of DNA's name. This sugar has a 5-carbon structure.

Nucleotide Structure: Each nucleotide is made of deoxyribose sugar, a phosphate, and one of the four nitrogenous bases: adenine, guanine, cytosine, or thymine.

Nucleotide Pairing: Adenine will always pair with thymine. Cytosine will always pair with Guanine. This is assuming there are no mistakes within DNA Replication. The reason for this is the number of covalent bonds needed between the bases. A-T has 2 bonds between them. C-G has 3 bonds between them.

DNA Replication: After the DNA is unzipped by DNA Helicase, the two single-stranded molecules will become double-stranded again in a 5' (5 prime) to 3' (3 prime) direction. One strand is called the leading strand and will be easily replicated with DNA Polymerase. The other strand, known as the lagging strand, will be replicated in sections. Both strands will need the use of an RNA primer to start the process and DNA Polymerase will make both strands double-stranded again.

It may be important to note that the lagging strand's sections are called Okazaki fragments. There are multiple RNA primers used to help the lagging strand become double-stranded again. DNA Polymerase adds these sections of base pairs, called Okazaki fragments, to the lagging strand to make it double-stranded again.

Two other important enzymes used at the very end of replication are DNA Ligase and exonuclease. Exonuclease will remove the RNA primers. DNA Ligase will go back and make sure it "glues" together all of the Okazaki fragments to make it one whole strand again.