BiologyChapter 12: Inheritance
Monohybrid Cross — Test Cross
Tall unknown x tt. All tall -> parent was TT.
Learning objectives
- Define test cross using accurate biology terms.
- Explain why test cross matters within monohybrid cross.
- Apply the learning unit to an FBISE-style example, comparison, diagram, or calculation.
Definition
Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. This page separates the idea from the wider topic “MONOHYBRID CROSS” so it can be revised and assessed on its own.
Important terms
- TEST CROSS
- Tall unknown x tt.
- MONOHYBRID CROSS
- One gene, two alleles, complete dominance.
Overview
Study this learning unit in three steps:
Key Idea
Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles.
Examples TT x tt -> all tall · Tt x tt -> 1 : 1 · Used in the exam a lot
Exam Application
Worked Tt x Tt (T tall). Gametes: T or t from each. Boxes: TT, Tt, Tt, tt. Genotype 1 : 2 : 1. Phenotype 3 tall : 1 dwarf.
Examples TT x tt -> all tall · Tt x tt -> 1 : 1 · Used in the exam a lot
WHAT — MONOHYBRID CROSS — TEST CROSS
Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. This page separates the idea from the wider topic “MONOHYBRID CROSS” so it can be revised and assessed on its own.
WHY — Why this topic matters
MONOHYBRID CROSS — TEST CROSS is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. Examples: TT x tt -> all tall; Tt x tt -> 1 : 1; Used in the exam a lot. Exam use: Worked Tt x Tt (T tall). Gametes: T or t from each. Boxes: TT, Tt, Tt, tt. Genotype 1 : 2 : 1. Phenotype 3 tall : 1 dwarf.
Explanation
Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. Examples: TT x tt -> all tall; Tt x tt -> 1 : 1; Used in the exam a lot. Exam use: Worked Tt x Tt (T tall). Gametes: T or t from each. Boxes: TT, Tt, Tt, tt. Genotype 1 : 2 : 1. Phenotype 3 tall : 1 dwarf.
In simple words
Federal Board Class 11 Biology learning unit. Easy wording; no provincial-board material added.
Key points
- cross with recessive
- 3 : 1
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Monohybrid Cross — Test Cross
Sticky Notes · Quick Revision
Core idea
- Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. This page separates the idea from the wider topic “MONOHYBRID CROSS” so it can be revised and assessed on its own.
WHAT
- Tall unknown x tt.
WHY
- MONOHYBRID CROSS — TEST CROSS is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW
- Tall unknown x tt. All tall -> parent was TT. Half dwarf -> parent was Tt. This reveals the hidden allele. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles. Examples: TT x tt -> all tall; Tt x tt -> 1 : 1; Used in the exam a lot. Exam use: Worked Tt x Tt (T tall). Gametes: T or t from each. Boxes: TT, Tt, Tt, tt. Genotype 1 : 2 : 1. Phenotype 3 tall : 1 dwarf.
Common misconception
- Do not treat test cross as the same as every other part of monohybrid cross; define this unit and use its own evidence, steps, or conditions.
FBISE exam check
- Define monohybrid cross — test cross, explain how it works, and support the answer with one relevant example.
60-second revision
- Tall unknown x tt.
- TT x tt -> all tall
- Exam link: cross with recessive.
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