Difference between Gene and Allele

Genes and Alleles are the two basic and most important terminologies in Genetics. In general, Gene is a basic and functional unit of heredity that is responsible for all genetic traits the human have, for example, hair colour, eye colour etc. Each cell in our human body has 25000-30000 genes. This gene has several variations which are responsible for unique characteristics of individuals like blue eyes, brown hair etc. These variations or changes in genes are known as an Allele. 

Keyterms: Gene, Allele, Genetics, Heredity, Genetic Trait, Nucleus, Chromosome, Cell, Eukaryotes, Prokaryotes, Cytoplasm, Bacteria, Animals, Plants, Fungi

Read Also: Chromosome Theory of Inheritance

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What is Gene?

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Gene is a functional unit of heredity, which is located in the chromosome of a cell. In Eukaryotes (Animals, plants and fungi) genes are located within the nucleus. In Prokaryotes(which doesn’t have a nucleus like some bacteria), genes are located in a single chromosome that is freely floating in the cell cytoplasm.

Genes are a section of DNA. Each gene has a unique set of instructions for particular functions. For example, the ABO gene is responsible for the blood group of individuals. Genes are responsible for traits that are inherited from parents like hair colour, height etc.

Fun Fact: The word “gene” was first coined in 1909, long after George Mendel’s experiment.

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What is an Allele?

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Allele is simply a different form of the same gene. It is responsible for unique features each human individual has like blue eyes, green eyes etc. An allele is found at a fixed location in a chromosome(locus). Dominant Allele and Recessive Allele are two types of Allele. Dominant Allele plays a major role in determining unique features

Fun Fact: In genetics, all human beings in the world are 99% identical

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Difference Between Gene and Allele

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Fun Fact: In 2017, scientists discovered that octopus and some kind of squids routinely edit their RNA to adapt to their environment.

Read Also: Difference Between Antigen And Pathogen

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Gene and Allele: Example

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A human gene is inherited from its parents i.e one gene(Allele) from each. For example, consider a family in which the father has a Brown hair genotype(BB) and the mother has a Red hair genotype(bb). Their children will get mixed alleles(Bb) and this depends on the instruction of alleles. 

If one allele dominates the instruction of another allele, it is a dominant allele and the one which accepts that will be the recessive allele. In this family, all the children will have the Bb genotype. If a child grows up and marries a partner who also has a Bb genotype. The children will have 4 types of genotypes BB, Bb, Bb and bb where bb is the recessive one which results in red hair for any one of the children. This is presented in punnett square below

B- denotes allele responsible for brown hair

b- denotes allele responsible for red hair

Like the above example, many genetic functions are passed from one generation to another.

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Mendel’s Experiment

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George Mendel is referred to as the father of Modern Genetics. He made his genetic inheritance experiment with two traits of flower(Purple and white) to analyse 7 different characteristics.

He cross-breeds the flowers of two different traits and waits for three offspring generations to see the trait results.

In the first generation of offspring, only one trait was expressed(purple). Then he crossed the first-generation offspring with each other. Approximately 75% of second-generation offspring expressed dominant first trait and 25% of second-generation offspring expressed recessive second trait which is lost in the first generation.

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Names of Genes and Their Functions

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Globin Gene: It is responsible for the production of haemoglobin in the human body, where haemoglobin is responsible for oxygen circulation in our body

ABO Gene: It is responsible for the Blood Group of individuals

BRCAI: It is responsible for controlling an early-onset form of Breast Cancer

RH Gene: Responsible for Controlling Rhesus Blood Type

CFTR Gene: It controls mucus and secretion from various glands

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Things to Remember

• Gene, a section of DNA responsible for traits inherited from parents whereas alleles are different forms of the same gene responsible for unique features of individuals
• Both Gene and allele are found in the locus of the chromosome, for eukaryotes it is found in the cell nucleus and for prokaryotes, it is found in the cell cytoplasm
• Gene cannot form pairs whereas Allele occurs only as a pair.
• Based on the gene copies from the parent, an allele is distinguished into homozygous(identical copies) and heterozygous(different copies)
• Gene determines the genotype of an organism where Allele determines the phenotype of an organism
• Punnett Square and George Mendel’s offspring genetic experiment are the best ways to understand genetic inheritance in a simplified manner. 

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Previous Year Questions

1. The science that deals with the application of principles….[CUCET 2010]
2. A 10 years old patient is found to have the following….[COMEDK UGET 2012]
3. Which of the following genes shows the heterozygous...[BHU UET 2008]
4. Which chromosomal constitution refers to Jacob's syndrome….[BHU UET 2012]
5. Which of the following is an example of intergenic gene….
6. Which of the following is not considered as a mutagen…
7. Haemophilia is an example of….
8. In order to lessen the suffering of phenylketonurics...[AMUEEE 2014]
9. In Mendel's experiments with garden pea, round seed shape..[JKCET 2015]
10. Genotypic and phenotypic ratio in monohybrid cross remains..[JKCET 2011]
11. Who proposed the chromosomal theory of inheritance ?….[CUCET 2010]
12. The children of a father with type 'O' blood and mother with type….[COMEDK UGET 2012]
13. Epicanthus skin fold above the eyes and transverse palmer….[COMEDK UGET 2007]
14. Distance between the genes and percentage of….[COMEDK UGET 2015]
15. Which one of the following is a sex-linked disease….​[CUCET 2010]