**Core Concept**
The Human Leukocyte Antigen (HLA) gene complex is a group of genes that play a crucial role in the immune system by encoding proteins responsible for presenting antigens to T-cells. The HLA genes are located on the short arm of a specific chromosome.

**Why the Correct Answer is Right**
The HLA genes are located on chromosome 6, specifically on the short arm (p arm) at position 6p21.3. This region of the chromosome is known as the major histocompatibility complex (MHC) in humans. The HLA genes are essential for the proper functioning of the immune system, and variations in these genes can lead to autoimmune diseases, transplant rejection, and other immunological disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not correct because chromosome 1 is not associated with the HLA gene complex.
**Option B:** This option is not correct because chromosome 11 is not linked to the HLA gene complex.
**Option C:** This option is not correct because chromosome 19 is not associated with the HLA gene complex.

**Clinical Pearl / High-Yield Fact**
The HLA gene complex is highly polymorphic, meaning that there are many different versions of the genes that can vary between individuals. This polymorphism is the basis for the matching of HLA types between donors and recipients in organ transplantation.

**Correct Answer:** D. 6