Understand and use the terms: dominant, recessive, phenotype, genotype, homozygous and heterozygous

SouravNovember 4, 2024

Answer

Understanding the terms related to genetics is essential for grasping how traits are inherited and expressed in organisms. Here’s a concise explanation of the key terms: dominant, recessive, phenotype, genotype, homozygous, and heterozygous.

Key Terms in Genetics

1. Dominant:
   • A dominant allele is one that expresses its trait even when only one copy is present in the genotype. This means if an individual has at least one dominant allele, the associated trait will be visible in the phenotype. For example, in pea plants, the allele for tall stems (T) is dominant over the allele for short stems (t). Thus, both TT (homozygous dominant) and Tt (heterozygous) individuals will display tall stems.
2. Recessive:
   • A recessive allele only expresses its trait when two copies are present (homozygous condition). If an individual has one dominant allele and one recessive allele, the dominant trait will mask the effect of the recessive trait. For instance, a plant with the genotype tt will exhibit the short stem phenotype, while Tt will not express this trait.
3. Phenotype:
   • The phenotype refers to the observable characteristics or traits of an organism, such as height, color, or shape. It is influenced by both the genotype (the genetic makeup) and environmental factors. For example, a plant’s phenotype could be tall or short based on its genetic makeup and growing conditions.
4. Genotype:
   • The genotype is the genetic constitution of an organism, specifically referring to the alleles present for a particular gene. It can be homozygous (having two identical alleles) or heterozygous (having two different alleles). For example, a pea plant can have a genotype of TT (homozygous dominant), tt (homozygous recessive), or Tt (heterozygous).
5. Homozygous:
   • An organism is said to be homozygous for a gene when it has two identical alleles at a specific locus on homologous chromosomes. This can be either homozygous dominant (e.g., TT) or homozygous recessive (e.g., tt). Homozygous individuals will consistently express the same phenotype for that trait.
6. Heterozygous:
   • An organism is heterozygous for a gene when it has two different alleles at a specific locus (e.g., Tt). In this case, the dominant allele typically determines the phenotype, while the recessive allele remains unexpressed but can be passed on to offspring.