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Different Types of Genes and Their Functions

In this different types of genes and their functions post we have briefly explained about different types of genes in human and their functions.

Around 200 different types of cells make up the human body, including bone cells, blood cells, skin cells, nerve cells, liver cells, and so on. These cells produce several organs that differ in structure and function due to the expression of different genes in these cells based on the needs of the various organs.

For example, the serum albumin gene is only active in liver cells (hepatocytes). Similarly, the insulin gene is solely expressed in the pancreas’ beta cells. Aside from that, while some genes are found in all cells of the human body, some of them are expressed in kidney cells, while others are expressed in liver cells, and so on.

Types of Genes in Human

House Keeping Genes

Constitutive types of genes in human are another name for house keeping genes. They are constantly expressing themselves since they are required to carry out basic cellular processes. In other words, they code for proteins that the cell need on a regular basis to accomplish essential cellular functions such as cell maintenance. As a result, under normal circumstances, they are always present and expressed in the cells. As a result, they are required for the existence of a cell, regardless of its function. Genes for glycolysis and the ATPase enzyme are two examples of housekeeping genes.

Non-constitutive Genes

These types of genes in human do not express themselves continually. They’re also known as “luxury” or “specialist” genes. They can be turned on and off depending on the needs of cellular reactions or activities. The gene for nitrate reductase in plants and the gene for the lactose system in E. coli are two examples. During an organism’s lifetime, they are inactive or switched off for the most of the time. Only when their products are required do they become active and express themselves in certain cells.

Structural Genes

They’re also known as cistrons because they’re protein-coding genes, which means they solely code for proteins and not RNA or other products. They are a continuous length of DNA that contains exons, which code for proteins, and introns, which are non-coding regions. Inside the cistron, these sequences appear again and alternately. They code for the creation of chemical compounds or proteins that are required for the cell’s morphological and functional characteristics. The structural gene is still controlled by the regulator gene, operator gene, and promoter gene, which are all located upstream of the cistron.

Pseudogenes

They are close or homologous to functional protein-coding genes, but because to a disordered open reading frame, they are unable to produce a functional protein (ORF). Similarly, they may look a lot like RNA encoding genes, but they can’t make an RNA transcript.

Transposons

They are genes or segments of DNA that can jump or travel from one spot in the genome to another; from one chromosome to another inside an individual’s genome, as the name implies. Nobel Laureate Mc Clintock (1951) identified jumping genes in maize when she noticed that a DNA fragment can jump from one position to another within a cell’s genome. They are mainly found at the chromosome’s telomeric region.

Single Copy genes

These types of genes in human exist as single copies. It has one physical location in a genome and can have orthologs or orthologous in other species.

Processed genes

They are found in eukaryotes and they lack introns. They are formed due to reverse transcription or retroviruses. Processed genes are mostly non-functional as they lack promoters.

Overlapping genes

They are DNA fragments that, by employing alternative reading frames or initiation codons, can code for many products or polypeptides. They are referred to as overlapping since they code for multiple products and do not code for a single product. They aren’t found in vertebrates or higher organisms. They are usually found in organelles, bacteria, animal viruses, nuclear eukaryotic genomes, DNA virus, RNA virus, and other types of viruses, such as x 174 and SV-40.

Split genes

They were discovered by Sharp and Roberts. They were awarded the Nobel Prize in 1993. It is a gene that contains a non-functional part along with the functional part. They possess extra or non-essential part interspersed with the essential or coding part. So, they have intervening sequences that do not code for a protein.

Multi genes

These are the groups of similar types of genes in human. They work or express continuously to fulfil the needs of a cell depending on a particular protein product. These genes are homologous genes and they are work for a particular pathway and they synthesize the product as per the demand of the cellular environment.

Regulator gene

It controls another gene. They turn on or off the transcription of structural genes. It controls the expression of structural genes of an operon through the synthesis of a repressor protein. It is called regulator as it regulates whether the cistron will be expressed or not. They code for repressor protein and are present upstream to the coding sequence of cistron or structural gene.

Operator gene

This types of genes in human acts as a switch, for example, if the repressor protein produced by the regulator gene binds in the operator region, it (operator gene) remains switched off and it does not allow the mRNA polymerase enzyme to move forward and transcribe the structural gene of cistron so it acts as a switch to turn on or off the transcription of the cistron.

Promoter gene

The promotor types of genes in human is located upstream (towards the starting point) of the structural gene in the cistron. Only when it is present and active can the cistron work or express itself. It serves as a binding site for the RNA polymerase enzyme, which binds to the cistron’s promoter region so that it may scan the nucleotides of structural genes and transcribe mRNA. As a result, the promoter gene is where the RNA polymerase binds.

Terminator gene

This gene (a segment or piece of DNA) is found downstream of the cistron, when transcription stops and the RNA polymerase enzyme separates from the DNA. As a result, it’s a DNA location where RNA polymerase activity comes to a halt and transcription ends.

Silencer gene

Other types of genes in human are silenced as a result of their actions. If a gene’s protein output is no longer required by the cell, the silencer gene will silence that gene.

Enhancer gene

These genes enhance the activities of other genes related to the production of a particular protein product when demand for this product is high in a cell.

Integrated gene

They might be found on distinct chromosomes or in different sections of the same chromosome. All of these genes are turned on at the same time because they are supposed to be involved in a metabolic process involving 10 or more enzymes.

So, 10 or more proteins are required for 10 or more enzymes, and 10 or more cistrons are necessary to produce the required number of proteins. All of these cistrons are protein-coding genes that turn on at the same time when the metabolic pathway is active.

Further Readings

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