EXAMPLES

Example pedigree charts & case studies

Explore annotated pedigree charts produced with standard clinical notation. Each case study illustrates a foundational inheritance pattern or family structure—complete with key visual cues, representative human conditions, and genotype deduction guidelines.

Autosomal recessive: cystic fibrosis pattern

A classic horizontal distribution where unaffected carrier parents produce an affected child. Because the causative allele is on an autosome, both sexes are affected with equal frequency, and the disease phenotype typically skips generations.

Key Genetics Cues

• Horizontal pattern: affected individuals cluster in a single generation of siblings.
• Parents of affected children are asymptomatic obligate carriers (often marked with a central dot).
• Both males and females are affected with equal probability (25% per pregnancy).

Representative Disorders

Cystic Fibrosis (CFTR), Sickle Cell Anemia (HBB), Tay-Sachs Disease (HEXA), Phenylketonuria (PAH).

Genotype Deductions

Both parents (Generation II) must be heterozygous carriers (Aa). The affected child (III-1) is homozygous recessive (aa), and unaffected siblings have a 2/3 chance of being carriers (Aa).

Open this template in maker → Autosomal recessive vs dominant guide

X-linked recessive: hemophilia pattern

A sex-linked transmission dynamic where the pathogenic allele resides on the X chromosome. Hemizygous males (XY) express the condition, while carrier females (XX) remain asymptomatic. Transmission flows through carrier mothers to affected sons, with zero father-to-son transmission.

Key Genetics Cues

• Distinct male-skewed prevalence across multiple generations.
• Carrier mothers pass the allele to 50% of sons (affected) and 50% of daughters (carriers).
• Father-to-son transmission is completely absent; an affected father passes his X to 100% of daughters.

Representative Disorders

Hemophilia A & B (F8/F9), Duchenne Muscular Dystrophy (DMD), Red-Green Color Blindness (OPN1LW).

Genotype Deductions

Carrier mother (I-2) is X^A X^a. Affected son (II-1) is X^a Y. All daughters of an affected male are obligate carriers (X^A X^a).

Open this template in maker → X-linked recessive pedigree guide

Mitochondrial inheritance: maternal transmission

Maternal cytoplasmic transmission of circular mitochondrial DNA (mtDNA). Because only the ovum contributes mitochondria to the zygote, an affected mother passes the altered mtDNA to all biological offspring, while affected fathers never transmit the condition.

Key Genetics Cues

• Maternal transmission: 100% of children born to an affected mother express the trait.
• Paternal transmission block: affected fathers have zero affected offspring.
• Unbroken maternal lineage with varying severity due to cellular heteroplasmy.

Representative Disorders

Leber Hereditary Optic Neuropathy (LHON), MELAS Syndrome, MERRF Syndrome, NARP.

Genotype Deductions

All mitochondria in Generation II derive from the affected mother (I-1). Offspring of affected son II-2 inherit wild-type mitochondria from their unaffected mother.

Open this template in maker → Mitochondrial inheritance guide

Three generations: family health history

A standardized three-tier pedigree capturing the proband, their immediate sibship, parents, aunts, uncles, and grandparents. This structure provides the clinical depth needed to evaluate cardiovascular risks, hereditary cancers, and multi-factorial family patterns.

Key Genetics Cues

• Numbered horizontal generation tiers (I, II, III) with individual numbering left-to-right.
• Proband designated with an arrow (P) to indicate the primary patient seeking assessment.
• Diagonal slashes indicate deceased ancestors with annotated ages and causes of death.

Representative Disorders

Hereditary Breast & Ovarian Cancer (BRCA1/2), Lynch Syndrome (MMR genes), Familial Hypercholesterolemia.

Genotype Deductions

Tracking multi-generational health records allows clinicians to calculate empirical risks and determine whether a family meets guidelines for genetic testing.

Open this template in maker → Family health history practical guide

Twins and complex relationships

Pedigree detailing twin zygosity and multi-branch relationships. A horizontal connector bar distinguishes monozygotic (identical) twins sharing 100% nuclear DNA from dizygotic (fraternal) twins sharing 50% on average, alongside former and consanguineous partnerships.

Key Genetics Cues

• Diagonal twin branch lines originating from a single point on the sibling descent line.
• Horizontal connector bar indicates monozygotic (MZ) twins; absent bar indicates dizygotic (DZ).
• Double union line indicates consanguinity (blood-related parents sharing a common ancestor).

Representative Disorders

Concordance evaluations in polygenic conditions, twin-to-twin transfusion syndrome, familial twinning.

Genotype Deductions

If one monozygotic twin develops a single-gene monogenic condition, the co-twin has a 100% genetic recurrence risk, mandating presymptomatic surveillance.

Open this template in maker → Twins and adoption notation guide

Adoption & non-biological descent

Pedigree demonstrating clinical conventions for separating biological ancestry from legal rearing. Enclosing an individual in square brackets and utilizing dashed descent lines allows healthcare teams to track genetic risk factors without compromising family social history.

Key Genetics Cues

• Square brackets [ ] enclose the adopted individual’s symbol.
• Solid vertical line indicates biological descent; dashed vertical line indicates adoptive descent.
• Directional dashed descent identifies children adopted into or out of the pedigree cohort.

Representative Disorders

Hereditary cardiac arrhythmia screening, adult adoptee health evaluations, pre-adoption genetic counseling.

Genotype Deductions

Genetic recurrence risks must be evaluated exclusively through biological parents (solid lines), avoiding erroneous risk assignment to non-biological siblings.

Open this template in maker → Twins and adoption notation guide

How to analyze an unfamiliar pedigree chart

Follow this standardized 4-step diagnostic protocol to determine the mode of inheritance in any unknown family pedigree.

Scan Generational Continuity

Determine whether the trait appears in every generation (vertical pattern typical of dominant or mitochondrial traits) or skips generations (horizontal pattern typical of recessive traits).

Analyze Sex Ratios

Count affected males and females. Equal distribution suggests an autosomal locus; heavily male-biased distribution points toward X-linked recessive inheritance.

Examine Critical Reproductive Crosses

Inspect children of affected fathers. Father-to-son transmission confirms autosomal inheritance; affected fathers passing the trait to all daughters and no sons indicates X-linked dominant; affected fathers with zero affected children indicates mitochondrial.

Assign Candidate Genotypes

Assign allele symbols (e.g. A and a) to each family member. Verify that the assigned genotypes account for all phenotypes without biological contradictions.

Frequently asked questions about pedigree examples

How can I adapt these example charts with my own family details?

Click "Open this template" under any example card. It loads the exact chart directly into the maker canvas, where you can rename individuals, adjust health statuses, and add or delete relatives.

Can I export these example charts for presentations or teaching handouts?

Yes. Every example can be exported as a high-resolution PNG, publication-ready vector SVG, or printable vector PDF with customizable headers and anonymization settings.

Why do small pedigrees sometimes fail to definitively prove an inheritance pattern?

In small human families (1–2 children per generation), chance deviations can mimic other patterns. For example, an autosomal recessive trait might appear in two consecutive generations by coincidence (pseudodominance), or an X-linked trait might only affect one male, requiring broader family testing.

Explore more pedigree tools and references

Ready to build your own chart? You can start with a blank pedigree canvas , assemble relatives in plain English with Quick Build , review standard symbols in the symbols guide , or follow our step-by-step how-to guide .

Open the free maker Browse all templates Symbols reference