Deoxyribonucleic acid, abbreviated as DNA, is the hereditary material present in almost all prokaryotes and eukaryotes. DNA is located at the cell’s nucleus, but there is some DNA present in the mitochondria known as mitochondrial DNA. Thus, every cell circulating in your body has the same type of DNA composition.
Types of DNA
The DNA structure is a double helix that resembles a twisted ladder. The structure was discovered in 1963 by James Watson and Francis Crick. The frame is of alternating deoxyribose, which is a sugar and phosphate molecule.
There are two types of DNA the autosomal DNA and mitochondrial DNA.
- Nuclear DNA or autosomal DNA: Nuclear DNA (nDNA) is present in the cell nucleus of eukaryotic organisms and acquired from both parents. The structure of nuclear DNA is composed of 46 chromosomes, whereby 23 are from the father and the other 23 from the mother.
- Mitochondrial DNA: Mitochondrial DNA is present in the mitochondria, and each cell contains about 100-1000 copies. Mitochondrial DNA is haploid, meaning it comes from one source, which is the mother. This type of DNA has a higher mutation rate than nuclear DNA.
There are also several forms of DNA based on structural diversity, as can
- A-DNA: This appears when the environmental humidity is less than 75% and is rarely present under normal physiological conditions. The double strands are antiparallel and formed by sugar phosphates using phosphodiester bonds. Viruses adapt this form of DNA as an adaptive mode of survival in harsh environmental conditions.
- B-DNA: Discovered based on X-ray diffraction patterns and existed under normal physiological conditions. Double strands of B-DNA run in opposite directions, and the two strands are held together by hydrogen bonds between the base units.
- C-DNA: This is the form DNA takes when subjected to relatively low humidity and specific ions like Li+ and Mg2+. This form is unstable and doesn’t occur naturally in living organisms. Both B and C-DNA contain similar nucleotide conformations but at different ratios.
- D-DNA: Lacks the Guanine (G) base unit making it a rare variant. This form of DNA forms under lower humidity than A-DNA.
- E-DNA: Is an extended or eccentric organismal DNA present in the environment. E-DNA is from cellular material shed by different organisms into the environment like skin, mucous, secreted fecal matter, hair, gametes, and carcasses. The DNA lasts about 7-21 days, depending on environmental conditions like exposure to acidity, heat, or radiation.
- Z-DNA: Stands out with its zigzag appearance. It consists of minor and major grooves as it’s a left-handed double helix. This form of DNA is present in eukaryotes, bacteria, and viruses. Based on recent studies, Z-DNA links to diseases like Alzheimer’s and Systemic lupus erythematosus through the presence of naturally occurring antibodies.
DNA Replication and Uniqueness
DNA replication is essential for the formation of new cells. In this case, the DNA in all-new cells must be an identical duplicate of the DNA in the starting cells. Because it controls cellular activity and general biological development, having a copy of the genetic “blueprint” is crucial. The double helix is unzipped and unwound in the DNA replication process above, and each split strand serves as a template for duplicating a new partner strand. Nucleotides (bases) are paired to synthesize the new partner strands into two new double helices.
In humans, DNA sequencing is a one-of-a-kind experience. Except in the rare instance of identical twins, no two individuals will have identical DNA. However, more than 99 percent of the approximately three billion base pairs that make up the human genome are identical in all individuals. The chimpanzee, our closest surviving cousin, shares 96 percent of our DNA. Despite the seeming high degree of similarity, humans and chimps have 40 million distinct DNA molecules.
The DNA structure comprises twisted strands with distinct grooves. There are two kinds of tracks in the DNA, minor and major grooves vital as they form different proteins. The major and minor grooves bind transcription factors that lead to protein formation.
The major grooves of DNA form when the base units are far apart, while the minor grooves form when the base units are close together, and the formation of the grooves can tell the base sequence of specific DNA molecules. The grooves are opposite each other and run throughout the entire DNA molecule. The grooves are vital as they play a crucial role in replication and transcription.
The major grooves are deep and wide, while the minor grooves are narrow and shallow. The proteins bind at the base of the DNA grooves by special forces like hydrogen bonds and other non-specific bindings. Thus, some proteins bind to the significant grooves while others attach to the minor grooves and bind to both.
Building blocks of DNA
DNA building blocks have three components:
- Deoxyribose, and
- Four nitrogenous bases: Adenine, Guanine, Cytosine, and Thymine.
In this instance, two of the base units, adenine, and guanine, are purines with a double-ring structure, while cytosine and thymine are pyrimidines with a single-ring structure. Furthermore, DNA is made up of nucleotides, which are smaller subunits. The liver synthesizes nucleotides, which are acquired through the food we eat.
Genes as Part of DNA
One of the major discoveries of contemporary science is the discovery that DNA contains the information blueprint (genes) for all living creatures and the processes that convert the DNA code into the material of life. From the tiniest bacteria to the largest plants and animals on the planet, all living things depend on DNA to survive.
DNA has much fewer biological “letters” than the English alphabet’s 26 letters, yet it contains instructions for how organisms live, reproduce, metabolize, develop, and die. This is possible through the help of genes that are designed to code for specific traits. A gene is defined as a segment of DNA that codes for a protein.
In essence, DNA stores information in the form of code in four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). The DNA base pairs with each other A with T, C with G, forming base units.
These genes are passed down from parents to offspring and carry with them some specific individual traits. Genes in a human being are a set from both the mother and father, but mitochondrial DNA is from the mother. Genes dictate a person’s eye color, IQ level, personality traits, and body type. Therefore, the sequence in which the bases appear plays a vital role in building and maintaining a living organism.
DNA has two biopolymer strands called polynucleotides and is further made of monomer units known as nucleotides. The nature of the strands is due to the base units. For example, A-T interacts via two hydrogen bonds, while C-G interacts via three hydrogen bonds of the opposite strand. The shape and structure of the DNA strand are more potent with the hydrogen and hydrophobic bonds between base units.
Functions of DNA
DNA plays an essential part in the body of living organisms. Here are a couple of reasons why DNA is vital.
- DNA plays an integral part in carrying genetic material present in every cell and faithfully replicates during cell division.
- The relationship between DNA and proteins plays a vital role in forming body structure, messengers, enzymes, and hormones.
- When DNA changes on rare occasions, it forms mutations which bring about genetic variations which bring about evolution.
- DNA stores the genetic information necessary for inheritance and provides instructions and life processes. The instruction is passed from parent to offspring through vertical gene transfer.
Role of DNA in Reproduction
Humans produce gametes, which are unique cells with just one set of 23 chromosomes, during sexual reproduction. During conception, the father’s DNA combines with the mother’s to form a new set of 46 chromosomes. This is how the characteristics of an ancestor are handed on to descendants.
A single chromosome determines the gender of children in a gamete. The chromosome in question may be either the X or the Y: two X chromosomes make a girl child, whereas XY creates a boy child. Different genes regulate how cells differentiate from one another when the fertilized egg divides, resulting in numerous human tissues, organs, and systems.
Role of DNA in Biochemistry
All the cell proteins that enable life are coded in DNA. DNA is transcribed into RNA, which acts as a primer for translation into proteins by the cell. The enzymes, hormones, and structural proteins that each cell needs are among them. Complex biochemical feedback systems determine the DNA genes to be expressed.
Genes regulate the shape of your nose and the size of your ears through cellular biochemical pathways. You may have birth abnormalities, such as a cleft palate, or genetic illnesses, such as cystic fibrosis and Down’s syndrome, if a gene is improperly coded, such as when a mutation in the DNA molecule occurs.
DNA can be Transcribed to Proteins
The “core dogma of molecular biology,” which explains how the cell transcribes DNA into RNA and then interprets that RNA into proteins, is one of science’s most fundamental concepts. The DNA unzips during transcription, allowing the cell to make a corresponding strand of messenger RNA or mRNA. This mRNA moves from the cell nucleus to the cytoplasm, where it is read by the ribosome and translated into a protein.
A codon is a sequence made up of three nucleotides that encodes one amino acid. Polypeptides are lengthy sequences of amino acids that join together. These fold into proteins, which play critical functions in the human body’s structure, function, and regulation. This is why a gene was defined earlier as a segment of DNA that codes for a protein.
Contact Modern Biology Inc for your DNA Experiments
The best way to understand the properties of DNA is through practical experiments. At Modern Biology Inc, we provide students with experiments on the properties of DNA. Our experiments come with the equipment and reagents required, so you don’t have to source any additional materials. Even better, our kits come with instructional manuals to guide students through. For more information, contact us at (765) 446-4220, or fill out a short online form for us, and we’ll get back to you ASAP!