Haplotype is

Options

A. A single genome
B. Major histocompatibility complex
C. Chain of HLA alleles inherited together
D. All the above

Answer

### Step-by-Step Text Solution:

1. **Understanding the Term "Haplotype":**
- A haplotype refers to a group of genes or alleles that are inherited together from a single parent. It is essentially a combination of alleles at multiple loci that are transmitted together.

2. **Breaking Down the Components:**
- The term "haplotype" is derived from two parts: "haplo" meaning haploid (a single set of chromosomes) and "type" referring to genotype (the genetic constitution of an individual).

3. **Role of HLA Alleles:**
- HLA (Human Leukocyte Antigen) alleles are specific genes that play a crucial role in the immune system. They help the body recognize which proteins are self-made and which are foreign, thus aiding in the protection against pathogens.

4. **Identifying the Correct Option:**
- The question presents several options regarding the definition of haplotype.
- Option 1: A single genome - Incorrect.
- Option 2: Major histocompatibility complex - Incorrect.
- Option 3: Chain of HLA alleles inherited together - Correct.
- Therefore, the correct answer is that a haplotype is a chain of HLA alleles inherited together.

5. **Conclusion:**
- Haplotype is best defined as a set of alleles that are inherited together, particularly referring to the HLA alleles which are crucial for immune response.