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Core Genetics & Mechanisms

Allele / Genotype / Phenotype

An allele is a specific version of a gene, a genotype is the combination of alleles an organism carries, and a phenotype is the observable outcome of that genetic makeup interacting with environmental factors.

Overview

At the heart of every genetic experiment—from basic Mendelian crosses to advanced preclinical mouse modeling—lie three foundational concepts: allele, genotype, and phenotype. These terms describe different layers of biological information: the sequence variants that define genes (alleles), the combinations of those variants in an organism (genotype), and the observable traits that result (phenotype).

Frequently Asked Questions

Does genotype always predict phenotype?

Not always. Modifiers, environmental factors, incomplete penetrance, and epigenetic influences can all contribute to variation in phenotypic outcomes, even among organisms with identical genotypes.

What's the difference between heterozygous and homozygous?

Heterozygous organisms carry two different alleles at a genetic locus, whereas homozygous organisms carry two identical alleles.

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Related Terms

Zygosity (Heterozygous vs Homozygous)

Describes whether the two copies of a gene in an organism are identical (homozygous) or different (heterozygous). Determining zygosity is crucial for interpreting phenotypes and designing experiments.

Breeding Scheme (Hetero × Hetero, etc.)

Planned mating strategies used to generate offspring of specific genotypes—such as heterozygous, homozygous, or compound mutant combinations—from established genetically modified lines.

Germline Transmission

The process by which a genetic modification introduced into an organism is passed on to its offspring through reproductive (germ) cells. It confirms that the engineered change is stably integrated into the genome and can be inherited by future generations.

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Point MutationMissense and Nonsense MutationsFrameshift MutationGain-of-Function vs. Loss-of-Function MutationsPromoter / Enhancer / Regulatory Element
View All TermsBaseline Phenotyping

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