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Causes of variation and phenotype development

Inheritance, variation and evolution • Variation and evolution

Key concepts

What you'll likely be quizzed about

  • Genetic variation refers to differences in DNA sequences among individuals of the same species.
  • Populations typically exhibit extensive genetic variation because sexual reproduction and inheritance combine different alleles in offspring, making identical genomes rare outside identical twins.
  • The genome contains thousands of genes, with diploid organisms having two copies of each gene; small differences in DNA sequences lead to trait variation.
  • Measuring genetic variation requires sampling across many individuals, as observed variation is dependent on sample size and method.
  • Reliable conclusions about extensive variation necessitate sufficiently large samples.

Flashcards

Test your knowledge with interactive flashcards

Why can two tall parents have a shorter child?

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Height results from genetic predisposition and environmental influences, such as nutrition, which can affect growth.

Key notes

Important points to keep in mind

Genetic variation is extensive because sexual reproduction mixes alleles.

Classify variation causes as genetic, environmental, or both and provide examples.

All heritable variants arise from mutations; size and type influence effect severity.

Genotype provides potential, while environment determines realized phenotype.

Insertions/deletions generally have greater effects than single-base substitutions due to frame shifts.

Variation measurement requires sufficiently large samples; many traits follow normal distribution.

Some phenotypic changes, such as scars and suntans, are purely environmental and not inherited.

Not all mutations are harmful; some are neutral or beneficial, influencing evolutionary change.

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