Allele

Definition

An allele is a variant form of a gene that occupies a specific position on a chromosome. Alleles can determine distinct traits by producing different expressions of a characteristic, such as flower color or seed shape. Each individual inherits two alleles for each gene, one from each parent, and these variations can be dominant or recessive, influencing the organism's phenotype.

5 Must Know Facts For Your Next Test

1. Alleles can be classified as dominant or recessive, where dominant alleles mask the effect of recessive ones in determining traits.
2. Different combinations of alleles result in various genotypes, which can lead to a range of phenotypes within a population.
3. In a diploid organism, such as humans, each gene typically has two alleles located on homologous chromosomes.
4. Mendel's experiments with pea plants revealed how alleles segregate during gamete formation, leading to predictable patterns of inheritance.
5. Alleles can undergo mutations, leading to new traits and genetic diversity within populations over generations.

Review Questions

• How do alleles contribute to genetic variation in a population?
  • Alleles contribute to genetic variation by providing different versions of genes that can produce varying traits within a population. When individuals with different alleles reproduce, their offspring inherit a combination of these alleles, resulting in diverse phenotypes. This variation is crucial for natural selection, as it allows populations to adapt to changing environments and can influence evolutionary processes.
• Explain the significance of Mendel's laws in understanding how alleles interact during inheritance.
  • Mendel's laws, including the Law of Segregation and the Law of Independent Assortment, are foundational to understanding how alleles interact during inheritance. The Law of Segregation states that during gamete formation, the two alleles for a gene separate so that each gamete carries only one allele. The Law of Independent Assortment explains how different genes independently separate from one another when reproductive cells develop. These principles help predict how traits are passed on through generations based on the combinations of alleles from both parents.
• Evaluate how linkage and crossing over affect allele distribution in populations over time.
  • Linkage and crossing over significantly affect allele distribution by influencing how genes are inherited together during meiosis. When genes are located close together on the same chromosome, they tend to be inherited together due to genetic linkage. However, crossing over during meiosis can break this linkage by exchanging segments between homologous chromosomes, creating new allele combinations. This process increases genetic diversity within populations and plays a crucial role in evolution by allowing for new traits to emerge and spread over generations.

Related terms

Gene: A segment of DNA that contains the instructions for building proteins, which ultimately determine traits in an organism.

Genotype: The genetic makeup of an individual, represented by the combination of alleles for a given trait.

Phenotype: The observable physical or biochemical characteristics of an organism, determined by its genotype and the environment.