**Core Concept**
Kernicterus is a bilirubin-induced neurological dysfunction that occurs in jaundiced newborns. It is characterized by the deposition of bilirubin in the basal ganglia, cerebellum, and other areas of the brain, leading to various neurological deficits.

**Why the Correct Answer is Right**
Hypotonia, or low muscle tone, is not typically associated with kernicterus. In contrast, children with kernicterus often exhibit hypertonia, which is increased muscle tone. The late features of kernicterus include sensorineural hearing loss, choreoathetosis (a movement disorder characterized by involuntary movements), and upward gaze palsy, among others. These symptoms are a result of the bilirubin-induced damage to the basal ganglia and other areas of the brain.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypotonia is not a characteristic feature of kernicterus; instead, children with kernicterus often exhibit hypertonia.
**Option B:** Sensorineural hearing loss is a known complication of kernicterus, making this option incorrect.
**Option C:** Choreoathetosis is a recognized late feature of kernicterus, resulting from damage to the basal ganglia.
**Option D:** Upward gaze palsy is also a known complication of kernicterus, caused by damage to the midbrain.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize the late features of kernicterus to diagnose and manage affected children. A high index of suspicion is necessary, as kernicterus can have a significant impact on a child's quality of life and cognitive development.

**Correct Answer:**
✓ Correct Answer: A. Hypotonia