SC.912.L.16.3: Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic information.
Deoxyribonucleic acid is a biochemical that exists within the cells of every organism and act as a blue print instructing the cell how to operate and construct proteins. DNA consists of monomer building blocks called nucleotides. There are 4 nucleotides; adenine, thymine, guanine, cytosine. Every nucleotide consists of 3 basic components; pentose sugar, phosphate group and a nitrogen base
Nucleotides bond together forming a twisted ladder structure known as a double helix.
Adenine forms complementary hydrogen bonds to the nucleotide Thymine. Cytosine forms complementary hydrogen bonds to the nucleotide Guanine. The genetic code that is commonly referred to is simply the order of the ATC and Gs in a section of DNA. What makes you genetically different than your classmates is that in many sections of your DNA the order of the letters is slightly different.
Prokaryote vs Eukaryote DNA
Prokaryotic DNA has a few distinct differences from eukaryotic DNA. The chromosomes of prokaryotic cells are always circular while eukaryotic chromosomes are usually linear. Circular means that the chromosomes are continuous while linear means the chromosomes actually have a beginning and an end.
Prokaryotic DNA tends to have only 1 origin of replication while eukaryotic dna has multiple origins of replication. Since eukaryotic chromosomes tend to have more genetic information they are larger in size and require the cell to start copying the chromosomes from multiple locations so that the dna can be copied quickly.
Since there is so much more dna in a eukaryotic cell special structures are needed to efficiently pack the DNA into the cell. These balls of protein (histones) are used to wrap the DNA tightly and forms super coiled structures that we call chromosomes.
DNA Replication
DNA replication is known as Semi-conservative because the double stranded DNA molecules is seperated and each side of the molecule is used as a template that instructs the cell on how to properly construct the other half of the molecule.
Insert Picture of Semiconservative Replication Model here
Key DNA Enzymes involved in replication
- Topoisomerase – Enzyme that untwists the double stranded DNA molecule. This makes the dna go from being a spiral shaped staircase to a ladder.
- Helicase – Enzyme that unzips the double helix dna molecule.The molecule must be untwisted by topoisomerase to expose the hydrogen bonds of the nucleotides.
- DNA Polymerase – Enzyme responsible for adding new nucleotides together in a chain to construct a complementary strand of DNA. This enzyme can only add nucleotides once helicase has unzipped the double stranded molecule and exposed complementary nucleotides.
