What are the units of heredity ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Heredity**: Heredity refers to the process by which traits and characteristics are passed from parents to their offspring. This process is fundamental in biology and genetics.

2. **Identifying the Units of Heredity**: The primary units of heredity are called genes. Genes are segments of DNA that contain the instructions for building and maintaining an organism.

3. **Gene Structure**: Genes are typically found in pairs, similar to chromosomes. In humans, each individual inherits one set of genes from each parent, resulting in pairs of genes.

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