by Gene
A gene is a hereditary unit of information stored in the DNA that encodes instructions for the synthesis of functional molecules, typically proteins or RNA molecules. Genes serve as the fundamental units of inheritance, carrying genetic instructions from one generation to the next. Each gene consists of a specific sequence of nucleotides along the DNA molecule. The information encoded in genes determines the traits and characteristics of organisms, influencing their development, growth, and functioning. Genes undergo processes like transcription and translation to produce functional products that contribute to the diverse biological functions and traits observed in living organisms.
Properties of Gene:
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Genetic Information:
Genes store hereditary information, encoding instructions for the synthesis of functional molecules.
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DNA Sequence:
Genes consist of specific sequences of nucleotides along the DNA molecule.
- Inheritance:
Genes serve as units of inheritance, passing genetic information from one generation to the next.
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Trait Determination:
The information encoded in genes determines the traits and characteristics of organisms.
- Transcription:
Genes undergo transcription to produce complementary RNA molecules.
- Translation:
The information in RNA is translated into proteins or directly contributes to various cellular functions.
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Genetic Variation:
Genes contribute to genetic diversity within populations and species.
- Mutability:
Genes can undergo mutations, leading to variations in genetic information.
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Gene Expression:
The process of gene expression involves the activation of genes to produce functional products.
- Regulation:
Gene expression is tightly regulated, influenced by cellular and environmental factors.
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Functional Products:
Genes produce functional products such as proteins or RNA molecules that contribute to cellular functions.
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Evolutionary Significance:
Genes play a crucial role in the evolution of species over time.
Allele
An allele is a variant or alternative form of a gene located at a specific position on a chromosome. Alleles arise through mutations or genetic variations and can result in different traits or characteristics in organisms. They occupy corresponding loci on homologous chromosomes and may be either dominant or recessive, influencing the expression of a particular trait. The combination of alleles an organism inherits determines its genotype, influencing the observable phenotype. Alleles undergo segregation during meiosis, contributing to genetic diversity in populations. The study of alleles is crucial in understanding inheritance patterns, genetic diversity, and the mechanisms underlying the inheritance of traits in living organisms.
Properties of Allele:
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Genetic Variation:
Alleles represent different forms or variants of a gene, contributing to genetic diversity within a population.
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Gene Loci:
Alleles occupy specific loci or positions on homologous chromosomes.
- Inheritance:
Alleles are inherited from parents and play a crucial role in passing genetic information from one generation to the next.
- Dominance/Recessiveness:
Alleles may be dominant, expressing their trait when present, or recessive, requiring two copies for expression.
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Genotype Influence:
The combination of alleles in an organism’s genotype influences its observable traits or phenotype.
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Mutation Source:
Alleles can arise through mutations or genetic variations in the DNA sequence.
- Segregation:
Alleles undergo segregation during meiosis, contributing to the variability of genetic information in gametes.
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Homozygous/Heterozygous:
An organism can be homozygous (having identical alleles) or heterozygous (having different alleles) for a particular gene.
- Expressivity:
Alleles may exhibit variable expressivity, leading to different degrees of trait expression.
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Genetic Diseases:
Certain alleles may be associated with genetic diseases or disorders when they carry mutations affecting normal functioning.
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Mendelian Inheritance:
Alleles follow Mendelian inheritance patterns, influencing the transmission of traits across generations.
Key Differences between Gene and Allele
| Aspect | Gene | Allele |
| Definition | Unit of hereditary information | Variant form of a gene |
| Location | Located on a specific chromosome | Occupies a specific gene locus |
| Forms | Single form in a population | Multiple forms in a population |
| Expression | Codes for a specific trait | Contributes to trait expression |
| Mutation Source | Subject to mutations, leading to variation | May arise through mutations, genetic variations |
| Inheritance | Passed from parents to offspring | Inherited from parents |
| Number in an Organism | Many genes in an organism | Multiple alleles for a gene |
| Loci Occupation | Specific gene loci on chromosomes | Occupies specific loci on homologous chromosomes |
| Role in Variation | Contributes to genetic variation | Contributes to allelic variation |
| Genetic Diseases | Mutations in genes may lead to genetic disorders | Certain alleles may be associated with genetic diseases |
| Dominance/Recessiveness | Genes may have dominant or recessive forms | Alleles may be dominant or recessive |
| Expression Control | Controlled by regulatory elements | Expression influenced by regulatory elements |
| Genotype Impact | Influences the overall genotype | Determines the specific genotype |
| Mendelian Inheritance | Follows Mendelian inheritance patterns | Alleles follow Mendelian inheritance patterns |
| Example | “Eye color” gene | “Blue eye” allele |
Key Similarities between Gene and Allele
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Genetic Basis:
Both genes and alleles are integral components of the genetic material that determines the traits and characteristics of organisms.
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DNA Sequence:
Both are composed of specific sequences of nucleotides along the DNA molecule, carrying genetic information.
- Inheritance:
Both genes and alleles are inherited from parents and play roles in passing genetic information to offspring.
- Variability:
Both contribute to genetic variability within populations, influencing the diversity of traits observed.
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Mutation Potential:
Both can undergo mutations, leading to the formation of new genetic variants.
- Expression:
Both genes and alleles play roles in determining the expression of traits in organisms.
- Regulation:
The expression of both genes and alleles is subject to regulation by cellular and environmental factors.
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Influence on Phenotype:
Both genes and alleles influence the observable phenotype or traits of organisms.
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Mendelian Inheritance:
Both follow Mendelian inheritance patterns, affecting the transmission of genetic information across generations.
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