Alleles are different versions of a gene that can exist at a specific locus on a chromosome. They can vary slightly in their sequence of nucleotides, leading to differences in the traits they express. This genetic variation is crucial for the process of evolution, as it provides the raw material for natural selection to act upon, enabling populations to adapt over time.
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Alleles can be dominant or recessive, which influences how traits are expressed in offspring.
In a diploid organism, each individual has two alleles for each gene—one inherited from each parent.
Mutation can create new alleles, contributing to genetic diversity within a population.
The study of alleles and their distribution can provide insights into evolutionary processes and relationships among species.
Molecular techniques, like DNA sequencing, have allowed scientists to identify and compare alleles across different organisms.
Review Questions
How do alleles contribute to genetic variation within populations?
Alleles introduce variation by providing different versions of genes that can result in diverse traits among individuals in a population. This genetic diversity is essential for natural selection because it allows some individuals to adapt better to their environments than others. Over time, these variations can lead to evolutionary changes as advantageous alleles become more common in the gene pool.
Discuss the role of dominant and recessive alleles in inheritance patterns observed in populations.
Dominant alleles mask the expression of recessive alleles in heterozygous individuals, which means that the phenotype reflects the dominant trait. In populations, this can lead to specific traits being more prevalent due to selective pressures. Understanding how these alleles interact is crucial for predicting inheritance patterns and evolutionary outcomes, as it affects which traits are passed on to future generations.
Evaluate how molecular evidence for evolution utilizes the concept of alleles to trace evolutionary relationships among species.
Molecular evidence for evolution relies on comparing the DNA sequences of different species to identify similarities and differences in their alleles. By analyzing these genetic variations, scientists can construct phylogenetic trees that illustrate evolutionary relationships and divergence points. This approach highlights how allelic variation contributes to speciation and helps us understand how organisms have adapted over time to their environments.
Related terms
Genotype: The genetic makeup of an organism, specifically the combination of alleles for a particular gene.
Phenotype: The observable physical or biochemical characteristics of an organism, determined by both its genotype and environmental influences.
Homozygous: A condition where an organism has two identical alleles for a particular gene, resulting in uniform expression of that trait.