Definition
What is a phenotype?
A phenotype is any trait of an organism that can be observed or measured. It ranges from visible features such as height, hair color or the shape of a pea seed to features that need a test to detect, such as blood type, the activity of an enzyme or the presence of a disease. The word is used both for a single trait and for the whole set of an organism's characteristics.
Phenotype results from the genotype working together with the environment. Diet, exercise, temperature and exposure to toxins can all change a phenotype, sometimes as strongly as genes do. The link between genotype and phenotype is rarely simple. A dominant allele gives the same phenotype in homozygotes and heterozygotes, many traits, such as height, depend on many genes at once, and incomplete dominance produces an in-between phenotype, like pink flowers from red and white snapdragon parents.
Mendel worked from phenotypes, counting seed colors and plant heights to infer the hidden genotypes behind them. Natural selection also acts on phenotypes, which is how they connect genetics with evolution.
Word parts
Where does the word “phenotype” come from?
- pheno-
- to show, to appearGreek phainein
- -type
- mark, modelGreek typos
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Terms that go with it
- GenotypeA genotype is the genetic makeup of an organism, either at one locus, such as Aa, or across its whole genome, including alleles it does not express.
- AlleleAn allele is any of the alternative forms of a gene or DNA sequence that can occupy the same position, or locus, on a chromosome.
- Dominant alleleA dominant allele is a version of a gene whose effect shows in the phenotype even when only one copy is present, masking a recessive allele.
- Natural selectionNatural selection is the process by which inherited traits that improve survival and reproduction become more common in a population over generations.
- Mendelian inheritanceMendelian inheritance is the pattern by which single genes pass from parents to offspring, following the laws of segregation and independent assortment.
- EpigeneticsEpigenetics is the study of chemical marks on DNA and its packaging proteins that switch genes on or off without changing the DNA sequence.
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