Allele vs Gene: Differences, Examples, and Importance
An allele is an essential term of genetics. Gene is the structural unit of the chromosome, which carries heredity from one generation to another. The alleles are the pair of genes, which is located in a specific area of the chromosome. On this page, we are going to define allele and discuss what is the meaning of allele.
Allele Definition - There are different variants of genes present in a chromosome. An allele is a variant of the gene, which locates in a chromosome's specific location as a pair of genes.
In the human chromosome, alleles are present in pairs and maintain the same trait. Therefore, humans are diploid organisms. Two similar alleles are present in each genetic locus, where one allele is inherited from each parent. Also, an allele can be two or more variants of a gene at one genetic locus. But all the alleles maintain the same trait at a genetic locus of the chromosome.
Alleles Meaning In Biology
Now, we will discuss alleles meaning. The word allele comes from the Greek word 'allos'. An allele is the modern formation of that word. The word 'allos' means other. In biology, an allele means different varieties of a gene. The alleles present in a particular genetic locus maintain the same trait. Though alleles are present in a locus as a pair, they can also be found in more than two numbers. In the human chromosome, alleles are present in a pair only to carry the heredity.
Genotype of Allele
Alleles are located in a particular location of the chromosome. The chromosome is the central unit of an organism. All the alleles present in an organism build its genotype. Genotype can be of two types depending on the similarity of the alleles.
When a pair of alleles are the same, they build homozygous genotypes. When the pair of alleles in a location are not similar, they build heterozygous genotypes. In the case of homozygous genotype, the allele is not dominant or recessive. But the heterozygous genotype includes one dominant allele. The dominant allele overrules the features of the recessive allele.
[Image will be Uploaded Soon]
Example of Allele
Now, we will be discussing some examples of alleles. Here, we are taking the example of a pea plant. The alleles for the colour of the flower build heterozygous genotype, where the purple allele is dominant, and white is recessive. For the height of the plant, tall is the dominant allele, and short is recessive. For the pea colour, the dominant allele is yellow, and the recessive allele is green. In these three cases, the dominant alleles overrule the recessive alleles' feature in the case of heterozygous genotype. Also, the eye colour and hair colour of human organisms can be observed as the example of alleles.
Difference Between a Gene and an Allele
There are some fundamental differences between gene and allele. The differences between a gene and allele are given below in a tabular form.
Solved Examples
1. Give an Example of an Allele.
Solution: The genetic locus of each gene that consists of two alleles for different characteristics can be seen in the pea plant. In an experiment, it was seen that, for colour, the plants are purple due to the dominant allele and white due to the recessive allele. In height, they are tall due to the dominant allele and short due to the recessive allele. Like these, the other traits are governed by the dominant alleles in the specific genetic locus.
Conclusion
Biology is a vital subject of the Class 10 curriculum. The students should read all the chapters of biology sincerely. In Class 10, the biology syllabus contains introductory chapters of some important conceptual topics. The students should read all the chapters for their future convenience. These chapters will help them in higher studies. Genetics is a vital part of biology. The students can easily learn the primary concept of genetics in Class 10 from this page.
FAQs on What Is an Allele?
1. What is an allele in biology?
An allele is one of two or more alternative forms of a gene that are found at the same position, or locus, on a chromosome. Alleles are responsible for the variations in inherited characteristics. For example, the gene for eye colour has multiple alleles, such as those for blue, brown, or green eyes.
2. What is the main difference between a gene and an allele?
A gene is a segment of DNA that codes for a specific trait (like flower colour), while an allele is a specific version of that gene (like the allele for purple flowers or the allele for white flowers). In essence, a gene is the instruction, and an allele is the particular variation of that instruction.
3. What are dominant and recessive alleles? Explain with an example.
A dominant allele expresses its trait even if only one copy is present in the genotype. A recessive allele only expresses its trait if two copies are present. For instance, in pea plants, the allele for tallness (T) is dominant over the allele for dwarfness (t). A plant with genotype TT or Tt will be tall, while only a plant with genotype tt will be a dwarf.
4. Where are alleles located in a cell?
Alleles are located at a specific, fixed position called a genetic locus on homologous chromosomes. Since diploid organisms like humans have pairs of homologous chromosomes (one from each parent), they have two alleles for each gene, situated at the same locus on each chromosome in the pair.
5. How do alleles determine an organism's traits or phenotype?
Alleles determine an organism's observable traits (phenotype) by controlling the production of specific proteins. The combination of alleles an organism possesses is its genotype. This genetic makeup dictates which traits are expressed. For example, if an individual is heterozygous (Aa), the dominant allele (A) will determine the phenotype, masking the effect of the recessive allele (a).
6. What are multiple alleles? Provide a common example in humans.
Multiple alleles exist when a gene has more than two allelic forms within a population. Although any single individual can only carry two of these alleles, more than two can exist in the gene pool. The most common example in humans is the ABO blood group system. The gene 'I' has three alleles: IA, IB, and i, which combine in different ways to produce the four blood types (A, B, AB, and O).
7. Can a single individual have more than two alleles for one gene?
No, a single diploid individual cannot have more than two alleles for one gene. This is because they inherit only one set of chromosomes from each parent, meaning they can only have a maximum of two alleles at any given genetic locus. However, the population as a whole can have many different alleles for that gene.
8. What is the importance of homozygous and heterozygous genotypes in genetics?
The distinction is crucial for understanding inheritance patterns.
A homozygous genotype (e.g., AA or aa) means an individual has two identical alleles for a gene. They are 'true-breeding' for that trait.
A heterozygous genotype (e.g., Aa) means having two different alleles. Such individuals are carriers of the recessive allele, which can be passed to offspring even if it's not expressed in the parent.
9. How do new alleles arise in a population?
New alleles are created through gene mutation, which is a random and permanent alteration in the DNA sequence of a gene. If this change occurs in a gamete (sperm or egg cell), it can be passed on to the next generation. This process is the ultimate source of all new genetic variation in a species, providing the raw material for natural selection and evolution.
