Autosomal disorders that do not follow Mendelian inheritance patterns are often categorized as complex or non-Mendelian disorders. Unlike classical Mendelian inheritance (dominant, recessive), these conditions arise from more intricate genetic mechanisms, which can include the following:

### 1. **Mitochondrial Inheritance:**

– **Mitochondrial DNA Mutations:** These disorders are passed down from the mother because mitochondria, which have their own DNA, are inherited maternally. An example is **Leber’s Hereditary Optic Neuropathy (LHON).**

### 2. **Multifactorial Inheritance:**

– **Complex Traits:** These involve interactions between multiple genes (polygenic) and environmental factors. Conditions like **Type 2 Diabetes**, **Heart Disease**, and **Cleft Lip/Palate** are influenced by both genetic predispositions and lifestyle or environmental factors.

### 3. **Genomic Imprinting:**

– **Imprinted Genes:** Certain genes are expressed in a parent-of-origin-specific manner. Disorders such as **Prader-Willi Syndrome** and **Angelman Syndrome** arise from the same genetic region on chromosome 15, but the disorder that manifests depends on whether the defective gene is inherited from the mother or the father.

### 4. **Trinucleotide Repeat Disorders:**

– **Expansion of DNA Repeats:** These involve the expansion of specific DNA sequences. Disorders like **Huntington’s Disease** and **Fragile X Syndrome** are caused by the abnormal repetition of trinucleotide sequences in the genome.

### 5. **Mosaicism:**

– **Somatic Mosaicism:** This occurs when some cells in the body have a different genetic makeup than others, leading to disorders that vary in severity depending on the distribution of the affected cells. An example is **McCune-Albright Syndrome**.

These non-Mendelian disorders are more complex in their inheritance patterns and may involve a combination of genetic, environmental, and stochastic factors. They often require more sophisticated approaches to diagnosis, risk assessment, and treatment.