Allele

Definition

An allele is a variant form of a gene that is located at a specific position on a specific chromosome. Alleles can result in different traits being expressed in an organism, such as flower color or blood type, and contribute to genetic diversity within a population. The interaction of alleles can lead to dominant and recessive traits, playing a vital role in inheritance patterns and evolutionary processes.

5 Must Know Facts For Your Next Test

1. Alleles can be classified as dominant or recessive, with dominant alleles masking the effect of recessive ones in heterozygous individuals.
2. An individual inherits one allele from each parent, resulting in two alleles for each gene that can interact to produce different phenotypes.
3. Different alleles for the same gene can arise due to mutations, contributing to variations in traits among individuals in a population.
4. In diploid organisms, alleles exist in pairs located on homologous chromosomes, which can undergo recombination during meiosis.
5. The study of alleles is fundamental to understanding Mendelian genetics and the laws of inheritance established by Gregor Mendel.

Review Questions

• How do alleles influence the expression of traits in organisms?
  • Alleles influence trait expression through their interactions as dominant or recessive variants. For instance, if an organism inherits one dominant allele for a trait and one recessive allele, the dominant allele will typically determine the phenotype. This relationship highlights how variations in alleles contribute to the diversity of traits observed in populations.
• Discuss how Mendel's experiments with pea plants contributed to our understanding of alleles and inheritance patterns.
  • Mendel's experiments with pea plants demonstrated how alleles segregate during gamete formation and how they combine during fertilization. By observing traits such as flower color and seed shape across generations, he established the principle of dominance and recessiveness. His findings laid the groundwork for the laws of inheritance, showing that traits are inherited based on the combination of alleles from both parents.
• Evaluate the role of alleles in evolution and how they contribute to natural selection.
  • Alleles play a crucial role in evolution as they create genetic variation within populations, which is essential for natural selection. Variations among alleles can lead to differences in fitness among individuals based on their traits. Over time, advantageous alleles become more common as those individuals better adapt to their environment, thereby driving evolutionary change and contributing to the diversity of life forms.

Related terms

Gene: A segment of DNA that encodes information for the synthesis of a specific protein or function, serving as the basic unit of heredity.

Homozygous: A genetic condition where an individual has two identical alleles for a particular gene, either dominant or recessive.

Phenotype: The observable physical or biochemical characteristics of an organism, determined by both genetic makeup (genotype) and environmental influences.