Genetics Terminology and Concepts Explained
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Genetics Terminology
Basic Concepts
- Trait: An inheritable characteristic of an organism.
- Gene: A DNA segment containing information that controls a specific trait.
- Allele: A variant form of a gene, often arising from mutations, contributing to hereditary variations.
- Locus (pl. Loci): The specific location of a gene on a chromosome.
Zygosity
- Homozygous Organism: Possesses identical alleles for a given gene (e.g., AA or aa).
- Heterozygous Organism: Possesses different alleles for a given gene (e.g., Aa).
Allele Interactions
- Dominant Allele: An allele that expresses its phenotype regardless of the paired allele.
- Recessive Allele: An allele that expresses its phenotype only when paired with an identical allele.
Genetic Inheritance Patterns
- Dominance (Dominant Inheritance): A dominant allele on a chromosome determines the expressed trait.
- Genotype: The complete set of an organism's genes.
- Phenotype: The observable expression of the genotype influenced by environmental factors.
- Test Cross (Back Cross): Crossing an organism with an unknown genotype with a homozygous recessive organism to determine the unknown genotype.
- Reciprocal Cross: A pair of crosses where the sexes associated with each genotype are reversed.
- Intermediate Inheritance: The heterozygous offspring exhibits a phenotype intermediate between the two homozygous parents.
- Codominance (Co-dominant Inheritance): Both alleles are simultaneously expressed in the heterozygous offspring.
- Linkage: Genes located close together on a chromosome tend to be inherited as a unit.
- Carrier: An individual carrying a recessive allele without expressing the corresponding trait.
Genetic Variation
- Mutation: A change in the DNA sequence that can be passed on to daughter cells.
- Aneuploidy: An abnormal number of chromosomes, either an extra (trisomy) or a missing one (monosomy).
- Euploidy: An abnormal number of haploid chromosome sets.
- Karyotype: A systematic arrangement of chromosome pairs, typically ordered by size.