The Structure of DNA
In this section, we will discuss the structure of DNA and its basic units. DNA, which stands for Deoxyribonucleic acid, stores genetic information in its sequence of bases, determining the genotype of an organism and the structure of its proteins. The basic units of DNA are nucleotides, each consisting of a deoxyribose sugar, a phosphate group, and a base, which can be adenine, guanine, cytosine, or thymine. These nucleotides are joined together by strong covalent bonds to form the sugar-phosphate backbone. The complementary base pairs in DNA are joined together by weak hydrogen bonds, allowing the strands to be easily separated. The base pair rule states that guanine will only bond with cytosine, and adenine will only bond with thymine. Additionally, DNA is a double-stranded double helix with antiparallel strands, where the two strands run in opposite directions.
DNA Organization in Prokaryotes and Eukaryotes
DNA is organized differently in prokaryotes and eukaryotes. In prokaryotic cells, such as bacteria, DNA is organized into circular chromosomes and plasmids, while in eukaryotic cells, DNA is tightly coiled into linear chromosomes and associated with proteins called histones. Eukaryotes also have small circular chromosomes within their mitochondria and chloroplasts.
Replication of DNA
DNA replication occurs before cell division, ensuring that each daughter cell has an identical copy of genetic information. The leading strand of DNA is replicated continuously, with DNA polymerase synthesizing a complementary strand in one continuous process. On the other hand, the lagging strand is replicated in fragments, which are then joined together by the enzyme ligase to form a complete complementary strand. DNA replication occurs at replication forks, where DNA is unwound and multiple replication forks can form at a time, increasing the speed of replication.
PCR & Gel Electrophoresis
The Polymerase Chain Reaction (PCR) is a procedure used to amplify small fragments of DNA for analysis in the lab. It involves repeated heating and cooling steps to allow the replication of specific DNA sequences. PCR has applications in paternity testing, DNA profiling, and genetic research. Gel electrophoresis is used to visualize the results of a PCR reaction, separating DNA fragments according to size by pulling them through a gel matrix with an electric current. DNA samples and a DNA ladder are used in gel electrophoresis to compare samples with known fragment sizes.
In conclusion, understanding the structure and replication of DNA is crucial in the study of biology, and these concepts have numerous practical applications in various fields of research and testing.
