What Is an Allele Definition Types and Inheritance
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.
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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 Allele in Genetics and How It Determines Traits
1. What is an allele?
An allele is an alternative form of a gene found at the same position (locus) on a chromosome. Alleles arise due to variations in DNA sequence and control specific traits in an organism.
- Each individual inherits one allele from each parent.
- Alleles can be dominant, recessive, or show other inheritance patterns.
- Example: The gene for eye color has different alleles for brown or blue eyes.
2. Where are alleles located in a cell?
Alleles are located at the same locus on homologous chromosomes within the cell nucleus. In diploid organisms:
- Chromosomes occur in pairs called homologous chromosomes.
- Each chromosome in the pair carries one allele for the same gene.
- Together, the two alleles influence the organism’s trait.
3. What is the difference between a gene and an allele?
A gene is a segment of DNA that codes for a trait, while an allele is a specific version of that gene.
- A gene determines a characteristic (e.g., flower color).
- Alleles are variations of that gene (e.g., purple or white).
- Different alleles arise due to mutations in DNA sequence.
4. What are dominant and recessive alleles?
A dominant allele expresses its trait even when only one copy is present, while a recessive allele expresses its trait only when two copies are present.
- Dominant alleles mask the effect of recessive alleles in heterozygous individuals.
- Recessive traits appear only in homozygous recessive conditions.
- Example: In pea plants, the tall allele (T) is dominant over the short allele (t).
5. What is a homozygous and heterozygous genotype?
A homozygous genotype has two identical alleles for a gene, while a heterozygous genotype has two different alleles.
- Homozygous dominant: AA
- Homozygous recessive: aa
- Heterozygous: Aa
6. How do alleles affect phenotype?
Alleles affect the phenotype by determining which version of a trait is expressed in an organism.
- The combination of alleles forms the genotype.
- The genotype interacts with environmental factors.
- Together, they produce the observable characteristic, such as height or blood type.
7. What are multiple alleles?
Multiple alleles refer to the existence of more than two allele forms of a gene within a population. Although an individual carries only two alleles, the population may have several variants.
- Example: The human ABO blood group system has IA, IB, and i alleles.
- These combinations produce blood types A, B, AB, or O.
8. Can alleles show incomplete dominance or codominance?
Yes, alleles can exhibit incomplete dominance or codominance depending on how they interact.
- Incomplete dominance: The heterozygous phenotype is intermediate (e.g., red and white flowers producing pink).
- Codominance: Both alleles are fully expressed (e.g., AB blood type).
9. How are new alleles formed?
New alleles are formed through mutations in the DNA sequence of a gene.
- Mutations can occur during DNA replication.
- They may involve base substitutions, insertions, or deletions.
- If the mutation is inherited, it becomes a new allele in the population.
10. Why are alleles important in genetics and evolution?
Alleles are important because they create genetic variation, which is essential for inheritance and evolution.
- Different alleles produce variation in traits.
- Natural selection acts on these variations.
- Over time, allele frequencies change, leading to evolution in populations.
