**Question:** Tissue transplanted between two people of identical genetic make up is called -

A. Allograft
B. Isograft
C. Xenograft
D. Heterograft

**Correct Answer:** B. Isograft

**Core Concept:** Tissue transplantation refers to the surgical procedure where one person's tissue is transplanted to another individual of the same species. This can involve different types of tissues, including skin, bone, muscle, blood vessels, and nerves. The compatibility of the donor and recipient plays a significant role in determining the success of the transplant.

**Why the Correct Answer is Right:** Isografts are transplants between genetically identical individuals, such as within the same family or from an identical twin to another twin. Since both individuals share the same genetic profile, the risk of immune system rejection is significantly reduced. This makes isografts more likely to be successful compared to allografts, xenografts, and heterografts.

**Why Each Wrong Option is Incorrect:**

A. Allografts: Transplants between individuals with different genetic backgrounds, which increases the risk of immune system rejection.
B. Isografts: Transplants between genetically identical individuals, which reduces the immune system rejection risk.
C. Xenografts: Transplants between individuals from different species, such as human to pig or mouse. Xenografts are not relevant to the question, as it asks for tissue transplants between humans with identical genetic backgrounds.
D. Heterografts: Transplants between individuals with different genetic backgrounds, which increases the risk of immune system rejection. This is similar to allografts, but here we focus on the different genetic profiles.

**Why the Correct Answer is Right:**

**Clinical Pearl:** The understanding of tissue transplant compatibility is crucial in clinical practice, particularly in familial diseases or genetic disorders where identical twins, siblings, or family members may require tissue transplantation. By recognizing the appropriate type of tissue transplant (e.g., isografts), physicians can minimize the risk of immune system rejection and improve the success rate of the procedure. This can significantly impact the patient's quality of life and prognosis in various medical conditions.