BiologyChapter 7: Inheritance
7.2 Genotypes and Phenotypes
Genotype:
Explanation level
Introduction
Genetics is the study of heredity and variation. To understand how traits are passed from parents to offspring, we need to know some basic genetic terms. These include genes, alleles, loci, genotype, and phenotype. This topic explains these terms and how they relate to inheritance.
Definition
Genotype: The genetic makeup of a trait at each locus is called the genotype.
Phenotype: The physical appearance of a trait is called the phenotype, which is determined by the genotype.
Main Idea
A discussion of Mendelian genetics usually requires an understanding of some basic genetic terms, such as:
- Gene
- Allele
- Genotype (homozygous or heterozygous)
- Phenotype (dominant or recessive)
- Genome
- Gene pool
These terms help explain how traits are inherited and expressed in living organisms.
Core Concept
Key Genetic Terms
| Term | Definition |
|---|---|
| Gene | A specific segment of DNA that encodes the sequence of amino acids in a particular polypeptide; unit of inheritance |
| Allele | Different forms or variations of a gene at the same locus |
| Locus (plural: loci) | Specific position of a gene on a chromosome |
| Genotype | The genetic makeup of a trait at each locus (e.g., EE, Ee, ee) |
| Phenotype | The physical appearance of a trait (e.g., free earlobes, attached earlobes) |
| Homozygous | Having two identical alleles for a particular gene (e.g., EE or ee) |
| Heterozygous | Having two different alleles for a particular gene (e.g., Ee) |
| Dominant | An allele that expresses its trait in the phenotype, even when paired with a different (recessive) allele |
| Recessive | An allele that only expresses its trait in the homozygous state |
| Genome | The complete set of an individual's genes |
| Gene pool | The complete set of all genes and their different alleles present in all individuals of a population |
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