BiologyChapter 12: Inheritance
Pedigree Idea
A pedigree is a family tree of a trait.
Learning objectives
- Explain pedigree idea in clear biological language.
- Distinguish 1. recessive hints from 2. dominant and x.
- Use the key terms to answer a short Federal Board exam question.
Definition
A pedigree is a family tree of a trait. Square male, circle female, shaded = shows the trait (school). Horizontal line = partnership; vertical = children. Autosomal recessive: can skip generations, two typical parents can have an affected child. Dominant: usually every generation. X-linked: look at sons and no father-to-son. 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.
Formula
vertical = children. Autosomal recessive
Important terms
- PEDIGREE IDEA
- A pedigree is a family tree of a trait.
- 1. RECESSIVE HINTS
- Affected child from two unshaded parents.
- 2. DOMINANT AND X
- Dominant: at least one shaded parent usual.
Overview
Read the tree, do not invent gossip:
Recessive Hints
Affected child from two unshaded parents. Consanguinity named as raising recessive risk in the school wording, not as a judgement essay. Two unaffected parents with affected child → autosomal recessive. Trait may skip a generation. Both parents must be carriers (heterozygous).
Examples aa is shaded · Aa unshaded carrier · Do not name real families
Dominant and X
Dominant: at least one shaded parent usual. X-linked recessive: more males; shaded male, unshaded parents, mother is the clue. Never use a pedigree to bully. Autosomal dominant: affected parent usually has affected child every generation. X-linked recessive: more affected males; no father-to-son transmission.
Examples Roman generations I, II · Birth order left to right · Question mark = unknown
WHAT — PEDIGREE IDEA
A pedigree is a family tree of a trait. Square male, circle female, shaded = shows the trait (school). Horizontal line = partnership; vertical = children. Autosomal recessive: can skip generations, two typical parents can have an affected child. Dominant: usually every generation. X-linked: look at sons and no father-to-son. 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.
WHY — Why this topic matters
PEDIGREE IDEA is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
RECESSIVE HINTS: Affected child from two unshaded parents. Consanguinity named as raising recessive risk in the school wording, not as a judgement essay. Two unaffected parents with affected child → autosomal recessive. Trait may skip a generation. Both parents must be carriers (heterozygous). Examples: aa is shaded; Aa unshaded carrier; Do not name real families. DOMINANT AND X: Dominant: at least one shaded parent usual. X-linked recessive: more males; shaded male, unshaded parents, mother is the clue. Never use a pedigree to bully. Autosomal dominant: affected parent usually has affected child every generation. X-linked recessive: more affected males; no father-to-son transmission. Examples: Roman generations I, II; Birth order left to right; Question mark = unknown. Exam: two unshaded parents shaded child. Trait can be autosomal recessive. Parents are heterozygous carriers. Child is homozygous recessive.
In simple words
Practice symbols. Not genetic counselling advice.
Key points
- square / circle
- skip or not
- skip a generation
- pattern not a person
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Pedigree Idea
Sticky Notes · Quick Revision
Core Idea
- A pedigree is a family tree of a trait. Square male, circle female, shaded = shows the trait (school). Horizontal line = partnership; vertical = children. Autosomal recessive: can skip generations, two typical parents can have an affected child. Dominant: usually every generation. X-linked: look at sons and no father-to-son. 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.
1. RECESSIVE HINTS
- Affected child from two unshaded parents. Consanguinity named as raising recessive risk in the school wording, not as a judgement essay. Two unaffected parents with affected child → autosomal recessive. Trait may skip a generation. Both parents must be carriers (heterozygous).
2. DOMINANT AND X
- Dominant: at least one shaded parent usual. X-linked recessive: more males; shaded male, unshaded parents, mother is the clue. Never use a pedigree to bully. Autosomal dominant: affected parent usually has affected child every generation. X-linked recessive: more affected males; no father-to-son transmission.
Exam Example
- Exam: two unshaded parents
- shaded child.
- Trait can be autosomal recessive.
- Parents are heterozygous carriers.
- Child is homozygous recessive.
Common Misconception
- Do not treat 1. RECESSIVE HINTS and 2. DOMINANT AND X as the same idea; each explains a different part of the topic.
FBISE Exam Check
- Define pedigree idea, explain the two key parts, and use the correct biological terms.
- Exam reminder: Exam: two unshaded parents shaded child. Trait can be autosomal recessive. Parents are heterozygous carriers. Child is homozygous recessive.
60-second revision
- A pedigree is a family tree of a trait.
- 1. RECESSIVE HINTS: Affected child from two unshaded parents.
- 2. DOMINANT AND X: Dominant: at least one shaded parent usual.
- Exam reminder: Exam: two unshaded parents shaded child. Trait can be autosomal recessive. Parents are heterozygous carriers. Child is homozygous recessive.
Did you understand this topic?
Your answer is saved with your learning record. It does not mark the topic as mastered.