Okay, let's tackle this question. The question is asking about a genetic term where a gene is inherited from only one parent. The options aren't provided, but the correct answer is supposed to be imprinted gene. Hmm, wait. Let me think.

First, I need to recall the different genetic terms. There's autosomal dominant, recessive, X-linked, etc., but those are about inheritance patterns, not about the gene being active from one parent. Then there's the concept of genetic imprinting, where a gene is expressed only if inherited from one parent. For example, if a gene is imprinted on the maternal side, the paternal copy is silenced and vice versa. So the term here is "genomic imprinting" or "imprinted gene."

Now, the options could include things like X-linked recessive, which is a different concept. Or maybe uniparental disomy, but that's when both copies come from one parent. No, the question is about a gene being inherited from one parent but active. So the correct term is imprinted gene.

Why are the other options wrong? Let's see. If an option was "autosomal dominant," that's a different pattern where one copy is sufficient for expression. "X-linked recessive" is about the location on the X chromosome. "Mitochondrial inheritance" is maternal since mitochondria come from the mother, but the question isn't about inheritance pattern. "Uniparental disomy" is when both copies come from one parent, which is different from imprinting where only one copy is active.

The clinical pearl here is that imprinting disorders like Prader-Willi and Angelman syndrome are examples where the gene is imprinted. So the key point is that the gene is expressed based on parental origin, not just inherited from one parent. That's the core concept. The correct answer is imprinted gene.

**Core Concept**
The question tests the understanding of **genomic imprinting**, a phenomenon where gene expression depends on the parent of origin. Unlike typical Mendelian inheritance, imprinted genes are silenced epigenetically depending on whether they are inherited from the mother or father.

**Why the Correct Answer is Right**
**Genomic imprinting** involves DNA methylation and histone modification to silence one parental allele. For example, *IGF2* (insulin-like growth factor 2) is paternally expressed and maternally silenced. This monoallelic expression ensures only one active allele, even though both alleles are inherited. The question specifically refers to the inheritance of a gene from one parent when the other allele is silenced, which defines imprinting.

**Why Each Wrong Option is Incorrect**
**Option A:** *X-linked recessive* refers to inheritance patterns on the X chromosome, not parental origin-based silencing.
**Option B:** *Autosomal dominant* describes inheritance where one functional allele suffices for expression, unrelated to imprinting.
**Option C:** *Uniparental disomy* involves inheriting both copies of a chromosome from one parent, not silencing of one allele.
**Option D:** *Mitochondrial inheritance* is strictly maternal due to maternal transmission of mitochondrial DNA, but this is distinct from nuclear gene imprinting.

**Clinical Pearl / High-Yield Fact**
Remember **Prader-Willi syndrome** (paternal deletion of 15q1

✓ Correct Answer: A. Genomic imprinting