IGCSE Biology 3 Views 1 Answers
State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment
State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment
Answer
Understanding the underlying causes of variation is crucial in the study of genetics and biology. The distinction between discontinuous and continuous variation highlights the different factors that contribute to phenotypic differences among individuals.
Discontinuous Variation
- Genetic Influence: Discontinuous variation is primarily caused by genetic factors. Traits that exhibit this type of variation are often controlled by one or a few genes, leading to distinct phenotypic categories.
- Examples: Traits such as ABO blood groups, seed shape in peas (round vs. wrinkled), and seed color in peas (yellow vs. green) are all determined by specific alleles, resulting in clear, non-overlapping phenotypes.
Continuous Variation
- Genetic and Environmental Influence: Continuous variation arises from the combined effects of multiple genes (polygenic inheritance) and environmental factors. This results in a range of phenotypes that fall along a continuum.
- Examples: Traits such as height, body mass, and skin color are influenced by several genes as well as environmental conditions like nutrition, climate, and lifestyle. As a result, individuals within a population can exhibit a wide variety of phenotypic expressions.
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