Gene and DNA-Definitions, Structure, and Functions Explained
Genes are units of heredity transferred from one generation to the next generation and are held to determine some characteristics of the offspring. The Word “ gene” was coined by Danish botanist Wilhelm Johnson in 1909. Gregor Mendel discovered that genes come in pairs and are inherited as distinct units. Genes are found on tiny structures called Chromosomes. Chromosomes are found inside the cells of our body. There is an important role of genes in determining physical traits. Information is carried by genes like whether a person has curly hairs or straight hairs, short legs or long legs. Most of these things are passed on from parents to their offspring.
Chromosomes are found in matching pairs or sets of two. There are hundreds or sometimes thousands of genes in just one chromosome. The chromosomes and genes are made up of DNA (deoxyribonucleic acid). Specific instructions are spelt out by DNA. DNA is just a cookbook recipe for the synthesis of proteins in the cells. Most of the things in our body are made up of proteins such as bones, teeth, hairs, earlobes, blood, muscles. Hence, they are considered as building blocks of the body. Proteins are essential for our body to work properly, the growth of our body, and to stay healthy. It is estimated by scientists that each gene makes as many as 10 different proteins in the body. It goes up to 300,000 proteins. The working of a gene can be explained with an example - Neera's mother has one gene for brown hair and one for red hair. She passed the brown hair gene to Neera. Neera's father has two genes for brown hair. Neera ended up with two genes for brown hair, one from each of her parents.
Gene Expression
The information encoded in a gene is used in the synthesis of a functional product like protein, and the process is known as Gene expression. While in non-protein-coding genes such as tRNA or small nuclear RNA genes result in the formation of a functional RNA as a product. DNA is transcribed into RNA, and this transcribed RNA is then translated into proteins. This is known as central dogma.
Stages of Gene Expression
Structural genes are those genes that code for the amino acid sequences. There are two stages involved in the process of gene expression.
Transcription
It is the process hatch that leads to the production of messenger RNA and the processing of the resulting mRNA molecule by using enzyme RNA polymerase.
Translation
It is the process in which mRNA is used to direct protein synthesis and also for the subsequent post-translational processing of the protein molecule. Other forms of RNA that play a role in transcription can also be produced by some genes. There are a number of components included in structural genes which are mentioned below.
Exons: Amino acids are coded by exons and they thoroughly determine the amino acid sequence of the protein product. Exons are the portions of genes that are represented in the final mature mRNA molecule.
Introns: These portions of the genes do not code for amino acids and are spliced (removed) from the mRNA molecule before translation.
What is DNA?
DNA, or deoxyribonucleic acid, is a complicated molecule that includes all of the information needed to construct and sustain an organism. It is a double-helix molecule that carries genetic instructions for all known species and many viruses' formation, functioning, growth, and reproduction. It is a mixture of two polynucleotides. This polynucleotide coils around itself, forming a double helix. All living organisms' cells contain DNA. In fact, practically every cell in a multicellular organism contains the whole set of DNAs needed for that organism. The whole set of your DNA is called your genome. There are 3 billion bases, 20,000 genes, and 23 chromosome pairs in it. Nucleotides constitute the DNA molecule. Each nucleotide is composed of three components: a sugar, a phosphate group, and a nitrogen base.
Structure of DNA
The DNA structure may be compared to a twisted ladder, and this structure is known as a double helix. It is a nucleic acid, and nucleotides are the building blocks of all nucleic acids. The DNA molecule is made up of units called nucleotides, and each nucleotide is made up of three separate components: sugar, phosphate groups, and nitrogen bases. The majority of DNA is contained inside a cell's nucleus, where it creates the chromosomes. Histones are proteins that attach to DNA on chromosomes. DNA is made up of two strands that twist together to form a spiral ladder known as a helix. DNA is composed of four nucleotide building blocks: adenine (A), thymine (T), guanine (G), and cytosine (C). Hydrogen bonds connect the complementary base pairs of guanine and cytosine, and adenine and thymine, respectively. The two strands of a DNA helix are held together by hydrogen bonds between complementary nucleotides. Each base has the ability to make hydrogen bonds with the outside world, such as water. In addition, the hydrogen bonds formed by each nucleotide's phosphate groups engage, causing two strands of DNA to create a helical helix. Genes are small strands of DNA that contain distinct genetic information. DNA contains the genetic information required for heredity, as well as for instructions and life processes. Vertical gene transfer transmits the instruction from parent to child.
The backbones of DNA and RNA are made up of phosphodiester links. When two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to generate two ester bonds, this is called a phosphodiester bond. This relationship is part of the "bond." C-O-PO2−-O-C. Although phosphodiesters are most commonly associated with DNA and RNA, they may also be found in other biomolecules, such as acyl carrier proteins.
Difference Between Genes and DNA
Deoxyribonucleic Acid (DNA)
DNA is the genetic material of organisms and it is located in the nucleus and nucleoid.
The information necessary for development, function, ng, and reproduction is stored in DNA.
A monomer that contains DNA is the nucleotide which consists of three groups, pentose sugar, a nitrogenous base, and a phosphate group. Phosphate and nitrogenous base are attached to pentose sugar.
DNA is stable even in alkaline conditions.
Gene
Gene is a specific nucleotide sequence.
Genes help to encode an amino acid sequence of a specific protein.
Genes are made up of DNA but few may have RNA.
Difference Between Genes and DNA
FAQs on Gene vs DNA: What Sets Them Apart?
1. What is the main difference between a gene and DNA?
The main difference is that DNA (Deoxyribonucleic acid) is the entire complex molecule that contains all genetic instructions for an organism, like a complete cookbook. A gene, on the other hand, is a specific segment or section of that DNA molecule, similar to a single recipe within the cookbook. Therefore, a gene is a functional unit of DNA that codes for a specific protein or functional RNA molecule.
2. In simple terms, what exactly is DNA?
DNA, or Deoxyribonucleic acid, is a long, double-helix shaped molecule that acts as the primary carrier of genetic information in all living organisms. It is made up of smaller units called nucleotides, which contain a phosphate group, a sugar group, and one of four nitrogen bases: adenine (A), guanine (G), cytosine (C), and thymine (T). The specific sequence of these bases determines the genetic code.
3. Which is larger: a DNA molecule or a gene?
A DNA molecule is much larger than a single gene. A gene is just a small, specific portion of a long DNA strand. An entire DNA molecule is condensed into a structure called a chromosome, and each chromosome contains hundreds to thousands of individual genes arranged in a specific order.
4. How are DNA, genes, and chromosomes related to each other?
These three components represent different levels of organisation of genetic material. The relationship can be understood as follows:
- DNA is the fundamental molecule that carries the genetic code.
- A gene is a specific, functional segment of this DNA.
- A chromosome is the highly condensed and coiled structure of a very long DNA molecule, which is wrapped around proteins called histones. Think of a chromosome as a single volume of an encyclopedia, a gene as a single entry or article in that volume, and DNA as the letters and words that make up the article.
5. If a gene is made of DNA, what distinguishes a 'gene' from a general 'DNA sequence'?
While all genes are DNA sequences, not all DNA sequences are genes. A gene is a specific DNA sequence that has a defined function, such as coding for a protein or a functional RNA molecule. It includes both coding regions (exons) and non-coding regulatory regions. A general 'DNA sequence' can refer to any stretch of DNA, including non-functional or 'junk' DNA, which does not code for any product but may have other structural or regulatory roles yet to be fully understood.
6. How does a gene use the DNA code to create a specific trait, like eye colour?
A gene creates a trait through a process called protein synthesis. The sequence of nucleotide bases in a gene for eye colour, for example, provides the instructions for building a specific protein (an enzyme). This enzyme then helps produce melanin, the pigment that determines the colour of the iris. The process involves two main steps:
- Transcription: The gene's DNA sequence is copied into a messenger RNA (mRNA) molecule.
- Translation: The ribosome reads the mRNA sequence and assembles the corresponding amino acids to build the specific protein. The amount and type of this protein (pigment) result in the observable trait of eye colour.
7. What is the difference between an organism's DNA and its genome?
The term DNA refers to the chemical molecule itself, the deoxyribonucleic acid. The term genome refers to the complete set of all DNA in an organism, including all of its genes and non-coding sequences. So, while your cells contain DNA molecules, your genome is the entire library of all your genetic information spread across all 23 pairs of chromosomes.
8. Can a random change in the DNA molecule affect a gene? What is this phenomenon called?
Yes, a random change in the sequence of nucleotides within a DNA molecule can certainly affect a gene. This phenomenon is called a mutation. If a mutation occurs within a gene, it can alter the instructions for making a protein, potentially leading to a non-functional protein or a protein with altered function. This can result in a different physical trait or, in some cases, a genetic disorder.
