key term - Dominant allele

Definition

A dominant allele is a variant of a gene that, when present, will determine the phenotype of an organism, overshadowing the effect of a recessive allele. In inheritance patterns, dominant alleles can mask the expression of recessive alleles, leading to predictable traits in offspring. This concept is crucial for understanding genetic variation and population dynamics.

5 Must Know Facts For Your Next Test

1. A dominant allele will be expressed in the phenotype even if only one copy is present, whereas a recessive allele requires two copies to manifest.
2. The presence of a dominant allele can lead to variations in traits like flower color in plants, where one color may dominate over another.
3. In a simple Mendelian cross between homozygous dominant and homozygous recessive organisms, all offspring will express the dominant trait.
4. Punnett squares are often used to predict the inheritance patterns of dominant and recessive alleles in offspring.
5. In population genetics, the frequency of dominant alleles can influence traits within a population over generations, impacting evolution.

Review Questions

• How does the presence of a dominant allele affect the expression of traits in an organism compared to recessive alleles?
  • A dominant allele affects trait expression by ensuring that its associated trait will appear in the organism’s phenotype, regardless of whether one or two copies are present. In contrast, a recessive allele requires two copies to show its trait. This means that when both types of alleles are present, the dominant one will mask the effect of the recessive one, leading to clear patterns of inheritance.
• Discuss how understanding dominant alleles contributes to predicting genetic outcomes in breeding experiments.
  • Understanding dominant alleles is key in breeding experiments because it allows scientists and breeders to predict which traits will appear in offspring. By knowing which parent carries a dominant allele and using tools like Punnett squares, they can calculate the probability of specific traits being passed on. This knowledge helps in breeding programs aimed at enhancing desirable characteristics in plants and animals.
• Evaluate how the concept of dominant alleles informs our understanding of genetic variation within populations and its implications for evolution.
  • The concept of dominant alleles is crucial for understanding genetic variation because it explains how certain traits can become more prevalent within a population over time. As dominant alleles confer advantageous traits, individuals expressing these traits may have higher fitness and reproductive success. This can lead to shifts in allele frequencies over generations, driving evolution. Additionally, studying how dominant and recessive alleles interact helps scientists predict how traits might change under environmental pressures or selective breeding.

Related terms

recessive allele:

A recessive allele is a variant of a gene that only expresses its trait in the absence of a dominant allele. An organism must inherit two recessive alleles for the trait to be expressed.

genotype:

The genotype refers to the genetic makeup of an organism, specifically the alleles it possesses for a particular gene, whether dominant or recessive.

phenotype:

The phenotype is the observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment.