Alleles

Definition

Alleles are the different forms of a gene that occupy the same position, or locus, on a chromosome. They determine the specific traits or characteristics that an organism will express.

5 Must Know Facts For Your Next Test

1. Alleles can be dominant, recessive, or codominant, which determines how they are expressed in the phenotype.
2. Organisms inherit one allele from each parent for every gene, and the combination of these alleles makes up the genotype.
3. Genetic variation within a population is created by the different possible combinations of alleles that can be inherited.
4. Mutations in genes can lead to the creation of new alleles, which can result in the expression of novel traits.
5. The study of alleles and their inheritance patterns is the foundation of classical genetics and the understanding of heredity.

Review Questions

• Explain the role of alleles in determining an organism's genotype and phenotype.
  • Alleles are the different forms of a gene that occupy the same position on a chromosome. The combination of alleles inherited from both parents makes up an organism's genotype. The genotype then determines the physical and biochemical characteristics, or phenotype, that the organism will express. Depending on whether the alleles are dominant, recessive, or codominant, they will be expressed differently in the phenotype.
• Describe how genetic variation is created through the inheritance of different allele combinations.
  • Genetic variation within a population is created by the different possible combinations of alleles that can be inherited. Since organisms inherit one allele from each parent for every gene, the possible combinations of alleles result in a diverse array of genotypes. This diversity in genotypes then leads to the expression of a wide range of phenotypes, contributing to the overall genetic variation within the population. Mutations in genes can also create new alleles, further increasing the potential for genetic variation.
• Analyze the importance of understanding alleles and their inheritance patterns in the field of genetics.
  • The study of alleles and their inheritance patterns is fundamental to the field of classical genetics and the understanding of heredity. By studying how different alleles are expressed and passed down through generations, geneticists can unravel the genetic basis of traits and characteristics. This knowledge is crucial for applications such as genetic counseling, disease diagnosis and treatment, selective breeding, and the development of genetically modified organisms. Understanding alleles and their inheritance is a cornerstone of modern genetics, enabling researchers to make significant advancements in our understanding of biological systems and their evolution.

Related terms

Genotype: The genetic makeup of an organism, including the specific alleles present for each gene.

Phenotype: The observable physical or biochemical characteristics of an organism, which are determined by its genotype and influenced by environmental factors.

Homozygous: A genetic condition where an organism has two identical alleles for a particular gene.