Alleles

Definition

Alleles are different versions of a gene that arise by mutation and are found at the same place on a chromosome. Each individual inherits two alleles for each gene, one from each parent, which can result in varying traits or characteristics. The combination of these alleles determines an organism's genotype, which influences its phenotype, or observable traits, and plays a crucial role in the process of sexual reproduction.

5 Must Know Facts For Your Next Test

1. Alleles can be dominant or recessive; dominant alleles will express their trait even if only one copy is present, while recessive alleles require two copies to be expressed.
2. The combination of alleles an individual carries contributes to genetic variation within a population, which is essential for evolution.
3. During sexual reproduction, alleles are shuffled through processes like independent assortment and crossing over, leading to new combinations in offspring.
4. Mutations in alleles can lead to changes in traits, some of which may be beneficial, harmful, or neutral to the organism's survival.
5. Mendel's experiments with pea plants laid the groundwork for understanding how alleles interact to determine traits and inheritance patterns.

Review Questions

• How do alleles contribute to genetic variation within a population?
  • Alleles contribute to genetic variation by providing different versions of genes that can lead to diverse traits among individuals. When individuals mate, they pass on their alleles, resulting in offspring with unique combinations. This genetic mixing increases diversity within the population, which is important for adaptation and evolution over time.
• Explain how dominant and recessive alleles interact during the inheritance of traits in sexual reproduction.
  • In sexual reproduction, dominant alleles will express their traits even if only one copy is present, while recessive alleles require both copies to be expressed. For example, if an individual inherits a dominant allele from one parent and a recessive allele from the other, the dominant trait will be observed in the phenotype. This interaction illustrates how traits are passed down through generations and how they can manifest differently based on allele combinations.
• Evaluate the impact of mutations on alleles and their role in evolution through sexual reproduction.
  • Mutations introduce new variations in alleles that can significantly impact an organism's phenotype. These changes can be beneficial, harmful, or neutral and may affect survival and reproductive success. As these mutations spread through populations during sexual reproduction—where genetic recombination occurs—they contribute to the overall genetic diversity. Over time, this process can drive evolution by allowing populations to adapt to changing environments or pressures.

Related terms

genotype: The genetic makeup of an organism, represented by the combination of alleles it possesses for a particular gene.

phenotype: The physical expression or characteristics of a trait in an organism, resulting from the interaction of its genotype with the environment.

homozygous: A condition where an individual has two identical alleles for a particular gene, which can influence the expression of certain traits.