What is the Difference Between Gen and allele?

Difference Between Gen and allele is that A gene is a fragment of DNA that stores genetic information for the synthesis of a protein or its regulation. An allele is each different version of a gene for the same protein. For example, the ABO gene encodes the ABO human blood group protein that has at least three alleles: A, B, and O.Difference Between Gen and allele

Genes determine the physical and biochemical characteristics that an individual will have. They manifest through visible physical features (phenotype), such as the color of the skin or eyes, in addition to the functioning of the organism.

An allele is a specific variation in the DNA sequence of a gene that determines how genetic characteristics will be expressed in the individual. For example, the androgen receptor gene has several alleles, one of which is associated with hair loss in men (baldness or androgenic alopecia).

Difference Between Gen and allele in Tabular Form

Gen Allele
Definition It is a DNA fragment that contains the genetic information for the synthesis of a protein. It is a possible variation of a gene in a species.
Types Coding genes: with information to synthesize proteins.

Non-coding genes: they act as regulators of protein synthesis.

Constituent genes: they are expressed continuously.

Housework genes: maintain the basic functions of the cell.

Optional genes: only expressed in certain conditions.

Inducible genes: they are expressed in response to certain stimuli.

Dominant alleles: it is expressed whenever it is present.

Recessive alleles: expressed only when presented in identical pairs.

Wild alleles: it is the allele that is predominantly expressed in the majority of the population of a species

Mutant alleles: any allele different from the wild.

Quantity In diploid eukaryotic cells occur in pairs, one from the father and one from the mother. For each gene, there can be multiple alleles.
Examples There is a gene for eye color, blood type, hair type, and skin color. Whether the eyes are blue or brown eyes; blood, type A or B; the hair, curly or straight, and the skin, light or dark.

What is a gene?

The gene is the functional unit of inheritance. It consists of a DNA fragment (deoxyribonucleic acid) that contains the genetic information for the synthesis of a protein. Proteins are macromolecules that perform the main functions of a cell.

The word “gene” comes from the Greek root genos, meaning ‘race’ or ‘origin’. Gregor Mendel (1822-1884) was the first to describe genes as “inheritance packages.”

The set of genes of an individual is known as a genome and determines the genotype or DNA sequence of the genome. The phenotype is represented by the visible and measurable characteristics and features of the living being.

The position on the chromosome of a gene is called a locus. For example, the insulin gene (INS) is found on chromosome 11 of humans at locus 11p15.5, while the gene for melanocortin receptor 1 (MC1R), responsible for skin pigmentation, is found in locus 16q24.3.

Characteristics of the genes

  • It is composed of DNA.
  • They are transmitted by parental inheritance.
  • There are about 20,000 genes in humans.
  • They are transcribed in the form of messenger RNA.
  • They may undergo changes that produce a genetic mutation, giving rise to alleles.
  • In eukaryotes, genes have coding sequences (exons) and non-coding sequences (introns).

How a gene works

In order for the gene information to be expressed as a protein, there are sequences in the DNA called promoters, which are the site of transcription initiation. The enzyme responsible for “gene reading” is RNA polymerase, which forms messenger RNA from the genetic sequence. Messenger RNA is then translated into proteins in the ribosomes.

Basically, the genes that transmit the specific biological characteristics of each living being, from one generation to another, are stored in the genes.

What is an allele?

An allele is any of the variations in the DNA sequence that a gene can adopt. Each gene can have two or more alleles, the difference of which can range from a single nucleotide to the addition or removal of a piece of its sequence.

Each individual inherits one allele from the father and another from the mother, for the same gene, which may be the same or different. If the alleles are equal, it is a homozygous individual; When the alleles are different, the individual is heterozygous.

The word allele is an abbreviation of allelomorph, it is composed of the Greek word allele- , which means ‘from one to another’, and – morphé, which means ‘form’.Difference Between Gen and allele

Characteristics of an allele

  • It can be caused by a simple replacement of a nucleotide, by insertion of nucleotides or by the elimination of nucleotides.
  • They occupy the same locus on chromosomes.
  • They can be “wild” when the allele is expressed predominantly in a species, or “mutant” when it differs from the wild. Difference Between Gen and allele
  • When dominant: it determines visible characteristics in the next generation.
  • When it is recessive: it is present, but without manifesting itself, in the set of visible features.
  • If there are two recessive alleles inherited from the parents, the features of these alleles are manifested.

Origin of the alleles

The alleles originate by substitution, insertion or elimination of nucleotides in the DNA sequence of the gene. For example, the Na 1.7 protein (which is a sodium channel) is encoded by the SCN9A gene that can have different alleles:Difference Between Gen and allele

Gen Change in gene sequence Allele
SCN9A A cytosine C is exchanged for a thymine T in position 829 829 C> T
SCN9A A cytosine C is exchanged for an adenine A at position 984 984 C> A
SCN9A A guanine G is exchanged for an adenine A at position 5067 5067 G> A
SCN9A A thymine T is inserted at position 2076 2076_2077insT
SCN9A Nucleotides from 3703 to 3713 are removed 3703_3713del

Alleles contain information about specific traits that each gene possesses. These features may manifest (it is possible to see them) or they may be hidden (even if they are present). For example, in rabbits the color of the coat is determined by the C gene that has four alleles:

  1. Brown color c +: brown rabbits are considered wild type, which is considered the “normal” phenotype.
  2. Albino color c : homozygous rabbits for this allele do not produce pigment and have white fur and pink eyes.
  3. Color chinchilla ch : these rabbits have a gray color.
  4. Himalayan color h : these rabbits are white but have dark fur on the legs, ears and nose.

When one of the alleles is expressed in the phenotype (it manifests itself), it is called dominant, while the allele that is not expressed in an individual is called recessive. For example, any rabbit with the dominant allele + will be brown ( + c, + c ch or + c h ). The recessive allele c will only be evident in homozygous rabbits cc.

Homozygous and heterozygous

Most diploid organisms have pairs of chromosomes inherited from both parents. Each of these chromosomes has an allele of a gene. If the two alleles located in the same place ( locus ) of their respective chromosomes are equal, the cell or individual is homozygous. When the alleles located in the same locus of the chromosome are different, they are called heterozygous.

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