BiologyChapter 12: Inheritance
Exam Response (inheritance)
Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip.
Learning objectives
- Explain exam response (inheritance) in clear biological language.
- Distinguish 1. ratios to memorise from 2. letter discipline.
- Use the key terms to answer a short Federal Board exam question.
Definition
Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip. Always show gametes then boxes. Use w() style: one statement a line. Pedigree charts use standard symbols: squares for males, circles for females, shaded for affected. Reading patterns (skip generation, male-only) suggests autosomal recessive or X-linked modes. Genetics exam answers require clear Punnett grids with gametes on edges, ratios stated, and terminology precise. Always show working — one mark per step.
Important terms
- EXAM RESPONSE (INHERITANCE)
- Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip.
- 1. RATIOS TO MEMORISE
- Mono 3:1.
- 2. LETTER DISCIPLINE
- Two letters per person.
Overview
Checklist:
Ratios To Memorise
Mono 3:1. Mono genotype 1:2:1. Dihybrid 9:3:3:1. Incomplete 1:2:1 phenotype. Test cross 1:1 or all dominant. 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 · RrYy x RrYy · Tt x tt
Letter Discipline
Two letters per person. X-linked: write Xh. Blood: IA not A alone if the mark scheme wants superscripts. Circle the asked phenotype. Dominant allele: capital letter (T = tall). Recessive: lowercase (t = dwarf). Genotype TT, Tt, tt. Phenotype: what you observe. Test cross: unknown × homozygous recessive.
Examples Independent assortment stated · Chance in small families · No CRISPR here
WHAT — EXAM RESPONSE (INHERITANCE)
Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip. Always show gametes then boxes. Use w() style: one statement a line. Pedigree charts use standard symbols: squares for males, circles for females, shaded for affected. Reading patterns (skip generation, male-only) suggests autosomal recessive or X-linked modes. Genetics exam answers require clear Punnett grids with gametes on edges, ratios stated, and terminology precise. Always show working — one mark per step.
WHY — Why this topic matters
EXAM RESPONSE (INHERITANCE) is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
RATIOS TO MEMORISE: Mono 3:1. Mono genotype 1:2:1. Dihybrid 9:3:3:1. Incomplete 1:2:1 phenotype. Test cross 1:1 or all dominant. 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; RrYy x RrYy; Tt x tt. LETTER DISCIPLINE: Two letters per person. X-linked: write Xh. Blood: IA not A alone if the mark scheme wants superscripts. Circle the asked phenotype. Dominant allele: capital letter (T = tall). Recessive: lowercase (t = dwarf). Genotype TT, Tt, tt. Phenotype: what you observe. Test cross: unknown × homozygous recessive. Examples: Independent assortment stated; Chance in small families; No CRISPR here. Worked 4-mark monohybrid: Parents Tt and Tt. Gametes T and t from each. Offspring 1 TT : 2 Tt : 1 tt. Phenotype 3 : 1 if complete dominance.
Worked example
- Worked 4-mark monohybrid:
- Parents Tt and Tt.
- Gametes T and t from each.
- Offspring 1 TT : 2 Tt : 1 tt.
- Phenotype 3 : 1 if complete dominance.
In simple words
No gene-edit protocol. Punnett only.
Key points
- show the grid
- state the ratio
- match the cross type
- do not drop a letter
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Exam Response (inheritance)
Sticky Notes · Quick Revision
Core Idea
- Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip. Always show gametes then boxes. Use w() style: one statement a line. Pedigree charts use standard symbols: squares for males, circles for females, shaded for affected. Reading patterns (skip generation, male-only) suggests autosomal recessive or X-linked modes. Genetics exam answers require clear Punnett grids with gametes on edges, ratios stated, and terminology precise. Always show working — one mark per step.
1. RATIOS TO MEMORISE
- Mono 3:1. Mono genotype 1:2:1. Dihybrid 9:3:3:1. Incomplete 1:2:1 phenotype. Test cross 1:1 or all dominant. If all offspring show dominant phenotype → parent was homozygous dominant. If half show recessive → parent was heterozygous. Essential for identifying hidden recessive alleles.
2. LETTER DISCIPLINE
- Two letters per person. X-linked: write Xh. Blood: IA not A alone if the mark scheme wants superscripts. Circle the asked phenotype. Dominant allele: capital letter (T = tall). Recessive: lowercase (t = dwarf). Genotype TT, Tt, tt. Phenotype: what you observe. Test cross: unknown × homozygous recessive.
Exam Example
- Worked 4-mark monohybrid:
- Parents Tt and Tt.
- Gametes T and t from each.
- Offspring 1 TT : 2 Tt : 1 tt.
- Phenotype 3 : 1 if complete dominance.
Common Misconception
- Do not treat 1. RATIOS TO MEMORISE and 2. LETTER DISCIPLINE as the same idea; each explains a different part of the topic.
FBISE Exam Check
- Define exam response (inheritance), explain the two key parts, and use the correct biological terms.
- Exam reminder: Worked 4-mark monohybrid: Parents Tt and Tt. Gametes T and t from each. Offspring 1 TT : 2 Tt : 1 tt. Phenotype 3 : 1 if complete dominance.
60-second revision
- Typical tasks: define allele; 3:1; 9:3:3:1; pink 1:2:1; ABO; XX/XY; haemophilia grid; pedigree skip.
- 1. RATIOS TO MEMORISE: Mono 3:1.
- 2. LETTER DISCIPLINE: Two letters per person.
- Exam reminder: Worked 4-mark monohybrid: Parents Tt and Tt. Gametes T and t from each. Offspring 1 TT : 2 Tt : 1 tt. Phenotype 3 : 1 if complete dominance.
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