Human genetic variation - skin pigmentation

Human genetic variation

Differences in DNA among individuals within or across populations.

Skin pigmentation

The coloration of a person's skin, determined primarily by melanin levels.

Modern synthesis

A theory in biology that combines Darwin’s theory of evolution with Mendelian genetics.

Biology of the trait

The biological foundation and mechanisms underlying a specific characteristic.

Trait variation across populations

Differences in traits among different groups of people.

Alleles

Different forms of a gene that can exist at a specific location on a chromosome.

Environmental variation

Differences in environmental factors that can affect trait expression.

Functional relationship

The link between a trait and its impact on survival and reproduction.

Adaptive traits

Characteristics that enhance an organism’s ability to survive and reproduce.

Gene flow

The transfer of genetic material between populations.

Genetic drift

Random changes in allele frequencies in a population over time.

Folate hypothesis

The idea that darker skin protects against UV radiation-induced folate depletion.

Melanin

The dominant pigment in human skin that absorbs ultraviolet radiation.

Melanocyte

A type of skin cell that produces melanin.

Melanosome

An organelle that produces and stores melanin.

Skin color determination factors

Melanin type, amount produced, and number of melanosomes influence skin pigmentation.

Polygenic trait

A trait influenced by multiple genes.

Cline

A gradient of variation in a trait across geographic space.

UV exposure

Radiation from the sun that can affect skin pigmentation.

Latitude

Distance north or south of the equator, affecting UV radiation exposure.

Folic acid

Another name for folate, essential for DNA synthesis and cell growth.

Vitamin D hypothesis

The idea that lighter skin evolved to enhance vitamin D production in low UV environments.

Rickets

A disease caused by vitamin D deficiency, leading to weak or soft bones.

Innuit

A group of indigenous people living in the Arctic regions.

Biological race

A classification that suggests that human populations have distinct biological differences.

Subspecies

A taxonomic category below species, used to classify populations with distinct traits.

Evolutionary time

The timescale over which evolutionary processes occur.

Social construction of race

The idea that race is a concept created by societal norms rather than biological differences.

Non-concordant traits

Traits that do not consistently co-occur and vary independently.

Health disparities

Differences in health outcomes among different demographic groups.

Racism as a source of health inequities

The idea that systemic racism, rather than genetic factors, leads to health disparities in populations.

Convergent evolution

The process whereby organisms not closely related develop similar traits due to similar environmental pressures.

Adaptive traits in humans

Traits that have evolved in response to environmental challenges facing human populations.

Human phenotypes

Observable physical characteristics of humans, such as skin color.

Genetic variation

Differences in the genetic makeup between individuals.

Evolutionary theory

A framework for understanding the diversity of life through evolution.

Physical traits and race

Using visible characteristics to categorize humans into races.

Adaptation

The process by which a species becomes better suited to its environment.

Geographic variation

Differences in traits that occur based on geographic location.

Phenotypic plasticity

The ability of an organism to change its phenotype in response to environmental conditions.

Selective forces

Environmental pressures that influence reproductive success and survival.

Trait adaptation

Modification of a trait for better suitability to an environment.