Incomplete Dominance and Codominance — Incomplete

Incomplete Dominance and Codominance — Incomplete

What is it?

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. This page separates the idea from the wider topic “INCOMPLETE DOMINANCE AND CODOMINANCE” so it can be revised and assessed on its own.

In simple words

• Neither allele hides fully.
• RR red
• Exam link: three phenotypes.

Important terms

INCOMPLETE: Neither allele hides fully.

INCOMPLETE DOMINANCE AND CODOMINANCE: Incomplete: heterozygote is in-between (red x white snapdragon -> pink school).

What you should learn

• Define incomplete using accurate biology terms.
• Explain why incomplete matters within incomplete dominance and codominance.
• Apply the learning unit to an FBISE-style example, comparison, diagram, or calculation.

Examples

• RR red
• Rr pink
• rr white

KEY IDEA

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant.

EXAM APPLICATION

Worked: IA i x IB i. Gametes: IA or i, and IB or i. Boxes: IAIB, IAi, IBi, ii. Children: AB, A, B, O possible (1:1:1:1 school).

Full school-level explanation

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. This page separates the idea from the wider topic “INCOMPLETE DOMINANCE AND CODOMINANCE” so it can be revised and assessed on its own.

Study this learning unit in three steps:

WHAT — INCOMPLETE DOMINANCE AND CODOMINANCE — INCOMPLETE

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. This page separates the idea from the wider topic “INCOMPLETE DOMINANCE AND CODOMINANCE” so it can be revised and assessed on its own.

WHY — Why this topic matters

INCOMPLETE DOMINANCE AND CODOMINANCE — INCOMPLETE is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.

HOW — How it works

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. Examples: RR red; Rr pink; rr white. Exam use: Worked: IA i x IB i. Gametes: IA or i, and IB or i. Boxes: IAIB, IAi, IBi, ii. Children: AB, A, B, O possible (1:1:1:1 school).

KEY IDEA

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant.

Remember

• three phenotypes

Examples

• RR red
• Rr pink
• rr white

EXAM APPLICATION

Worked: IA i x IB i. Gametes: IA or i, and IB or i. Boxes: IAIB, IAi, IBi, ii. Children: AB, A, B, O possible (1:1:1:1 school).

Remember

• AB, A, B, O

Examples

• RR red
• Rr pink
• rr white

Remember

• three phenotypes
• AB, A, B, O
• Federal Board only
• three phenotypes
• AB, A, B, O
• three phenotypes
• independent learning unit
• three phenotypes

How the ideas connect

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. Examples: RR red; Rr pink; rr white. Exam use: Worked: IA i x IB i. Gametes: IA or i, and IB or i. Boxes: IAIB, IAi, IBi, ii. Children: AB, A, B, O possible (1:1:1:1 school).

Deeper understanding

Go beyond memorising Incomplete Dominance and Codominance — Incomplete. Connect the definition to reasons, relationships, exceptions, and exam wording.

How the ideas connect

Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a chemistry way; it is gene expression. Snapdragon: RR = red, rr = white, Rr = pink (blend). Phenotype ratio 1:2:1 matches genotype ratio — unlike complete dominance where heterozygote looks dominant. Examples: RR red; Rr pink; rr white. Exam use: Worked: IA i x IB i. Gametes: IA or i, and IB or i. Boxes: IAIB, IAi, IBi, ii. Children: AB, A, B, O possible (1:1:1:1 school).

Common mistakes

Exam focus

Core idea

WHAT

WHY

HOW

Exam focus

Quick revision

• three phenotypes
• AB, A, B, O
• Federal Board only
• INCOMPLETE: Neither allele hides fully.
• INCOMPLETE DOMINANCE AND CODOMINANCE: Incomplete: heterozygote is in-between (red x white snapdragon -> pink school).
• WHAT — INCOMPLETE DOMINANCE AND CODOMINANCE — INCOMPLETE: Neither allele hides fully. 1 : 2 : 1 of three phenotypes. Do not call pink a 'mix of paint' in a ch

Federal Board Class 11 Biology learning unit. Easy wording; no provincial-board material added.

For long answers on Incomplete Dominance and Codominance — Incomplete: define clearly → explain the main parts → give one example → state one exam caution.