Carrier

Definition

An individual who has one recessive disorder allele but does not show the disorder because the other allele is dominant.

Used by AQA, Edexcel and OCR

Specification 4.6.1.6, 4.6.1.7 · Paper 2

A person who has one copy of a recessive allele but does not express its phenotype because a dominant allele is also present.
The child must have received a recessive allele from each unaffected parent, making both parents heterozygous carriers.
Revise: Analysing Inheritance using Family Trees
An individual who has one recessive disorder allele and one dominant unaffected allele, does not have the disorder, but can pass on the recessive allele.
Revise: Inherited Disorders

1
Read the key before interpreting any symbol: shading normally marks the phenotype being tracked, not automatically a carrier.
2
Do not assume that an unshaded person in a pedigree lacks the recessive allele: an unaffected person may be a heterozygous carrier.

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Specification 3.14, 3.16, 3.18B · Paper 1

A person who is heterozygous for a recessive allele and can pass it on without showing the recessive characteristic.
Revise: Monohybrid Inheritance
Revise: Calculating Outcomes
An individual who has a recessive allele for a disorder but does not show the disorder; for an X-linked recessive disorder, this is usually a heterozygous female.
Revise: Sex-Linked Disorders

Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)

A person with one copy of a recessive allele who does not show the associated characteristic but can pass the allele to offspring.
For a recessive condition, a carrier has one copy of the recessive allele and may be unaffected, but can pass that allele on. If both prospective parents carry the relevant allele, inheritance information can be used to estimate the probability that an offspring will inherit the condition.
Revise: Genetic Testing and Medicine