STRUCTURE & FUNCTIONS OF DNA
NOTE!
This is an essay written on the above mentioned topic. It has been added under additional topics, as it may include information one might find helpful, or information that has not been discussed in much detail in the notes section. DO NOT COPY PASTE THIS.
You may use it as inspiration if citation is given.
​
Author: Amina Haider
Date added: 26th August 2018
UNIT: Heredity-evolution, biotechnology, interactions with organisms
STATEMENT OF INQUIRY: "The transformation of genetic material into inherited traits connects individuals to one through another patterns of inheritance"
KEY CONCEPT: Relationships
RELATED CONCEPTS: Function, Interaction, Patterns
GLOBAL CONTEXT: Scientific and Technical Innovation
Deoxyribonucleic acid (DNA) was first discovered by Frederich Miescher, a German biochemist, in 1869, but it was not until 1953 that James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins figured out the structure of DNA (a double helix) which could carry biological information. For their discovery, the four were awarded the 1962 Nobel Prize in Medicine (Rettner, 2013).
​
“DNA, or deoxyribonucleic acid is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA” (USA.gov, 2017). Most of the DNA is located in the cell nucleus, and hence called ‘nuclear DNA’, but some of the DNA can also be found in the mitochondria, where it is called mitochondrial DNA or mtDNA.
​
The information in DNA is stored as codes made up of four chemical bases – Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). Human DNA is made up of around 3 million bases, and more than 99% of those bases are the same in all people.The orders of these bases determine the characteristics and buildup of the organism (USA.gov, 2017).
​
Figure 1 (USA.gov, 2017)
Adenine and Thymine pair up, while Guanine and Cytosine pair up to make base pairs. Each base pair is attached to a phosphate and sugar molecule, and together a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a double helix.
​
DNA can replicate, and each strand of DNA in the double helix serves as a pattern for duplicating the sequence of patterns in the bases. The replication of DNA is critical as when cells divide, the two daughter cells need to have the exact copy of DNA present in the original cell (USA.gov, 2017).
​
The phosphate and sugar make up the backbone of the DNA, while the bases act as the connections between the phosphate-sugar backbones. DNA strands are very long, and to fit inside cells, they are tightly coiled to form chromosomes. Each chromosome contains a single DNA molecule. Each human has 23 pairs of chromosomes found inside the cell’s nucleus (23 from each parent) (Rettner, 2013).
​
Figure 2 Bonding in a DNA molecule (OpenStax CNX, 2017)
The DNA segments that carry genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the expression of genetic information. The major function of DNA is to encode the sequence of amino acids residues in proteins, using genetic code through the process of transcription (B, Johnson, & J, 2002).
​
The structure of DNA is such that it easily allows the replication of itself. As DNA is formed as a double helix, with each base on one strand directly related to another base on the other strand of DNA, during cell replication when RNA (through the process of transcription) copies the genetic information from both single DNA strands, and mRNA decodes this information at a ribosome or through cell division, the DNA is copied perfectly, and can easily fit with the other single strands copied. Hence the structure of DNA is in a double helix format, the copy of one of the single DNA strand will perfectly fit with the copy of the other single strand of DNA. This discovery of the double helix in DNA is the most important discovery in understanding how the function of DNA is directly based on DNA’s structure (B, Johnson, & J, 2002).
​
In conclusion, the main job of DNA is to store hereditary information and replicate it to help proteins synthesize in cells. DNA stores all the genetic information of the organism, which determines its characteristics and various traits. The structure of DNA (double helix), and the way it is bonded together (two DNA strands in a chromosome have a non-covalent bond), allows easy transcription and later translation. This makes the copying and transferring of genetic material much easier. This is an important function of the body, as whenever each cell divides the DNA is copied and given to the two daughter cells, and the process of transcription in protein synthesis is also important in cell activity. Hence, the double helix structure of DNA determines the DNA’s function and makes it easier.
​
References
B, A., Johnson, A., & J, L. (2002). The Structure and Function of DNA. New York: Garland Science.
​
OpenStax CNX. (2017). Structure and Function of DNA. Retrieved September 13, 2017, from Lumen
Mircrobiology: https://courses.lumenlearning.com/microbiology/chapter/structure-and-function-of-dna/
​
Rettner, R. (2013, June 6). DNA: Definition, Structure & Discovery. Retrieved September 13, 2017, from
Live Science: https://www.livescience.com/37247-dna.html
​
USA.gov. (2017, September 12). What is DNA? Retrieved September 13, 2017, from Genetics Home
Reference: https://ghr.nlm.nih.gov/primer/basics/dna