Neurobiology and Genetics of Mental Disorders Practice Questions

Q: IQ related genes have recently been found on which chromosome?

Chromosome X. **Explanation:** The correct answer is **Chromosome X**. Intelligence is a complex polygenic trait, but research in behavioral genetics has consistently highlighted the disproportionate role of the X chromosome in determining IQ. **Why Chromosome X is correct:** The X chromosome contains a high density of genes related to brain development, synaptic plasticity, and cognitive function. It is estimated that the X chromosome contains approximately **three times more genes** linked to mental function than any other autosome. This genetic concentration explains why many forms of intellectual disability (e.g., Fragile X Syndrome) are X-linked and why there is a higher prevalence of both very high and very low IQ scores among males (the "Greater Male Variability Hypothesis"). **Analysis of Incorrect Options:** * **Chromosome 21:** While Trisomy 21 (Down Syndrome) is the most common chromosomal cause of intellectual disability, the chromosome itself is not considered the primary "hub" for general intelligence genes in the healthy population. * **Chromosome 10 & 18:** While various loci on these chromosomes have been implicated in psychiatric conditions (such as bipolar disorder or schizophrenia), they do not harbor the specific concentration of cognitive-related genes found on the X chromosome. **High-Yield Clinical Pearls for NEET-PG:** * **X-linked Intellectual Disability (XLID):** Over 100 genes on the X chromosome are known to cause intellectual disability when mutated. * **Fragile X Syndrome:** The most common inherited cause of intellectual disability, caused by a CGG trinucleotide repeat expansion on the **FMR1 gene** (located on the X chromosome). * **Heritability of IQ:** The heritability of intelligence increases with age, ranging from ~20% in infancy to ~80% in late adulthood.

Q: Memory impairment is most likely to occur in which condition?

Down Syndrome. **Explanation:** **Down Syndrome (Trisomy 21)** is the correct answer because it is fundamentally associated with intellectual disability and progressive cognitive decline. The underlying medical concept involves the overexpression of the **Amyloid Precursor Protein (APP) gene**, which is located on chromosome 21. This leads to the early deposition of beta-amyloid plaques and neurofibrillary tangles, identical to those seen in **Alzheimer’s Disease**. By age 40, almost all individuals with Down Syndrome develop these neuropathological changes, making memory impairment a hallmark feature as they age. **Analysis of Incorrect Options:** * **Alkaptonuria:** This is an autosomal recessive metabolic disorder (deficiency of homogentisate 1,2-dioxygenase). It presents with dark urine, ochronosis (pigmentation), and arthritis, but does not typically involve primary memory impairment. * **Attention Deficit Hyperactivity Disorder (ADHD):** The core deficits are inattention, hyperactivity, and impulsivity. While patients may have trouble with "working memory" due to poor focus, they do not suffer from the structural memory loss or dementia seen in Down Syndrome. * **Conduct Disorder:** This is a behavioral disorder characterized by a repetitive pattern of violating the basic rights of others and societal norms. It is a disorder of behavior and personality, not a cognitive or memory-based pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Down Syndrome & Alzheimer’s:** Down syndrome is the most common genetic cause of early-onset Alzheimer’s disease. * **Dual Diagnosis:** In children with Down Syndrome, the most common comorbid psychiatric conditions are ADHD and Oppositional Defiant Disorder (ODD). * **Screening:** Periodic screening for cognitive decline is recommended for all Down Syndrome patients starting in their 30s.

Q: Maximum heritability is seen in which of the following conditions?

Schizophrenia. **Explanation:** Heritability refers to the proportion of variation in a trait that can be attributed to genetic factors. In psychiatric genetics, **Schizophrenia** consistently demonstrates one of the highest heritability rates among major mental illnesses. 1. **Why Schizophrenia is Correct:** Twin studies and large-scale genomic analyses show that the heritability of Schizophrenia is approximately **80%**. If one monozygotic (identical) twin has the disorder, the risk for the other twin is nearly 40-50%, compared to a 1% risk in the general population. This strong genetic loading makes it the most heritable condition among the given options. 2. **Analysis of Incorrect Options:** * **Mania (Bipolar Disorder):** While Bipolar Disorder also has high heritability (approx. 70-75%), it is generally ranked slightly lower than Schizophrenia in most standardized psychiatric textbooks used for NEET-PG. * **Depression (Unipolar):** Major Depressive Disorder has a significantly lower heritability rate, estimated at **30-40%**. Environmental factors and life stressors play a much larger role here than in Schizophrenia. * **Panic Disorder:** This has a moderate heritability of approximately **40%**. While it runs in families, the genetic influence is not as dominant as in psychotic disorders. **High-Yield Clinical Pearls for NEET-PG:** * **Risk of Schizophrenia:** * General Population: 1% * One Parent affected: 10-12% * Both Parents affected: 40% * Dizygotic Twin: 12-15% * Monozygotic Twin: 47-50% * **Order of Heritability (High to Low):** Autism/ADHD (>80%) > Schizophrenia (80%) > Bipolar Disorder (70%) > Depression (35%). * **Note:** If "Autism" or "Bipolar Disorder" are options alongside Schizophrenia, always check for the most updated consensus, but Schizophrenia remains the classic "high heritability" answer in traditional MCQ formats.

Q: Which psychological disorder is most commonly associated with myxedema?

Depression. **Explanation:** **Myxedema**, the clinical manifestation of severe hypothyroidism, is most commonly associated with **Depression**. Thyroid hormones play a crucial role in regulating neurotransmitters like serotonin and norepinephrine; a deficiency leads to a "slowing down" of both metabolic and psychological processes. Patients typically present with psychomotor retardation, lethargy, cognitive dulling (pseudodementia), and a low mood that mimics Major Depressive Disorder. **Analysis of Options:** * **B. Depression (Correct):** It is the most frequent psychiatric manifestation of hypothyroidism. In some cases, depression may be the presenting symptom before physical signs of myxedema appear. * **A. Mania:** Mania is typically associated with **hyperthyroidism** (thyrotoxicosis), where an excess of thyroid hormone leads to agitation, emotional lability, and heightened arousal. * **C. Phobia:** Phobic disorders are anxiety-based and do not have a direct, established pathophysiological link with myxedema. * **D. Paranoia:** While severe hypothyroidism can lead to "Myxedema Madness" (psychosis with paranoid delusions), it is much less common than the depressive symptoms seen in the majority of patients. **High-Yield Clinical Pearls for NEET-PG:** * **Myxedema Madness:** A term used for the rare state of psychosis, hallucinations, and paranoia occurring in severe hypothyroidism. * **Screening Rule:** Always rule out thyroid dysfunction (TSH levels) in any patient presenting with a first episode of depression or cognitive decline. * **Rapid Cycling Bipolar Disorder:** Hypothyroidism is a known risk factor for the development of rapid cycling in Bipolar Disorder. * **Treatment:** Psychiatric symptoms often resolve with Levothyroxine (T4) replacement, though adjunctive antidepressants may be needed initially.

Q: Which of the following brain areas is less likely to play a role in depressive disorder?

Corpus callosum. ### Explanation Depressive disorders are primarily associated with structural and functional abnormalities in the **limbic-cortical circuit**, which regulates emotion, executive function, and memory. **Why Option D is Correct:** The **Corpus Callosum** is a white matter structure responsible for interhemispheric communication. While some studies suggest subtle changes in white matter integrity in chronic depression, it is primarily a structural bridge rather than a functional center for emotional processing. Compared to the other options, it is the "least likely" to be a primary driver of depressive pathology. **Why Incorrect Options are Wrong:** * **A. Amygdala:** This is the emotional center of the brain. In depression, the amygdala often shows **increased activity**, correlating with heightened negative affect and anxiety. * **B. Hippocampus:** This area is crucial for memory and learning. Chronic depression is strongly linked to **hippocampal atrophy** (decreased volume) due to hypercortisolemia (stress-induced neurotoxicity). * **C. Anterior Cingulate Cortex (ACC):** The ACC acts as an interface between emotion and cognition. Reduced volume and activity in the subgenual ACC (Brodmann area 25) are hallmark findings in major depressive disorder (MDD). **NEET-PG High-Yield Pearls:** 1. **Neurobiology of MDD:** Associated with **decreased** volume of the Hippocampus and Prefrontal Cortex, but **increased** activity in the Amygdala. 2. **Subgenual ACC:** This is a specific target for Deep Brain Stimulation (DBS) in treatment-resistant depression. 3. **HPA Axis:** Depression is often characterized by a failure of the dexamethasone suppression test, indicating hypercortisolemia. 4. **Neurogenesis:** Antidepressants (like SSRIs) are thought to work partly by increasing **BDNF** (Brain-Derived Neurotrophic Factor), which promotes neurogenesis in the hippocampus.

Q: Which of the following substances is considered an anxiolytic?

Neuropeptide Y. **Explanation:** **Neuropeptide Y (NPY)** is the correct answer because it is a potent endogenous **anxiolytic** peptide found in high concentrations in the amygdala and hippocampus. It acts as a natural "buffer" against stress by counteracting the effects of Corticotropin-Releasing Factor (CRF). High levels of NPY are associated with resilience to stress, while low levels are linked to anxiety disorders and PTSD. **Analysis of Incorrect Options:** * **Caffeine (Option A):** A methylxanthine that acts as an adenosine receptor antagonist. It is a well-known **anxiogenic** (anxiety-inducing) substance that can trigger panic attacks in susceptible individuals by increasing sympathetic outflow. * **Cholecystokinin (CCK) (Option B):** A peptide hormone that, when administered (specifically CCK-4), acts as a potent **panicogen**. It induces acute panic symptoms and is often used in research to study panic disorder. * **Carbon Dioxide (CO2) (Option C):** Inhalation of 5% or 35% CO2 is a classic **anxiogenic** stimulus. It triggers the "suffocation alarm" in the brainstem, leading to hyperventilation and acute anxiety/panic. **High-Yield Clinical Pearls for NEET-PG:** * **Panicogens (Anxiogenics):** Caffeine, CCK, CO2, Sodium Lactate, and Yohimbine (alpha-2 antagonist). * **Anxiolytics:** Benzodiazepines (GABA-A facilitators), Buspirone (5-HT1A partial agonist), and NPY. * **NPY & PTSD:** Research indicates that individuals with higher NPY levels show better recovery from trauma, making it a target for future pharmacological treatments.

Q: Which chromosomal abnormality is associated with tall stature and aggressive or criminal behavior?

XYY. ### Explanation **Correct Option: B (XYY Syndrome)** XYY Syndrome, also known as **Jacob’s Syndrome**, is a chromosomal anomaly where a male has an extra Y chromosome. The classic clinical triad associated with this condition is **tall stature**, **severe acne**, and **behavioral problems**. Historically, it was linked to an increased risk of aggressive or antisocial behavior and was overrepresented in prison populations (the "Super-male" theory). While modern psychiatry notes that most XYY individuals are not criminals, for competitive exams like NEET-PG, the association with **impulsivity, lower IQ, and aggressive outbursts** remains a high-yield diagnostic marker. **Incorrect Options:** * **A (XXY - Klinefelter Syndrome):** This is the most common sex chromosome disorder. While it also presents with tall stature, it is characterized by **hypogonadism, gynecomastia, and infertility**. Patients are typically shy and passive rather than aggressive. * **C & D (XXXY and XXYY):** These are rare variants of Klinefelter syndrome. While they involve more severe intellectual disability and skeletal anomalies due to the extra X chromosomes, they are not the classic association for the "criminal genotype" described in psychiatric literature. **High-Yield Clinical Pearls for NEET-PG:** * **Jacob’s Syndrome (XYY):** Look for keywords like "tall stature," "antisocial behavior," and "normal fertility" (unlike Klinefelter). * **Fragile X Syndrome:** The most common *inherited* cause of intellectual disability; look for large ears and macro-orchidism. * **Down Syndrome:** The most common *chromosomal* cause of intellectual disability; associated with early-onset Alzheimer’s disease. * **Psychiatric Comorbidity:** XYY individuals have a higher prevalence of ADHD and Autism Spectrum Disorders.

Q: Stimulation of which of the following nerves causes an elevation in mood?

Vagus Nerve. **Explanation:** The correct answer is **Vagus Nerve (Cranial Nerve X)**. **Vagus Nerve Stimulation (VNS)** is an FDA-approved neuromodulation therapy for treatment-resistant depression. The underlying medical concept involves the stimulation of the afferent fibers of the vagus nerve, which project to the **nucleus tractus solitarius (NTS)** in the medulla. From the NTS, signals are sent to key mood-regulating areas of the brain, including the **locus coeruleus** (increasing norepinephrine) and the **raphe nuclei** (increasing serotonin). This modulation of neurotransmitter systems and the limbic system results in an antidepressant effect and elevation of mood. **Why other options are incorrect:** * **Olfactory (CN I) and Optic (CN II) Nerves:** These are purely sensory nerves dedicated to smell and vision, respectively. While sensory experiences can influence mood, direct electrical stimulation of these nerves is not a recognized clinical treatment for mood disorders. * **Trigeminal Nerve (CN V):** While Trigeminal Nerve Stimulation (TNS) is being researched for epilepsy and ADHD, it is not the primary or established "gold standard" cranial nerve stimulation used for mood elevation in psychiatric practice compared to the Vagus nerve. **High-Yield Clinical Pearls for NEET-PG:** * **VNS Indications:** Used for Treatment-Resistant Depression (TRD) and refractory epilepsy. * **Mechanism:** Increases levels of Norepinephrine and Serotonin in the brain. * **Side Effects of VNS:** Most common include hoarseness of voice, cough, and throat pain (due to proximity to the recurrent laryngeal nerve). * **Other Neuromodulation:** Do not confuse VNS with **Deep Brain Stimulation (DBS)**, which targets the Subgenual Cingulate Cortex (Area 25) for depression.

Q: Cortical blindness with confabulation is seen in?

Anton syndrome. ### Explanation **Correct Option: B. Anton syndrome** Anton syndrome (also known as Anton-Babinski syndrome) is a rare condition where a patient is **cortically blind** but adamantly denies their vision loss. The hallmark of this syndrome is **anosognosia** (lack of insight into a deficit) and **confabulation**. When asked to describe their surroundings, the patient will invent detailed visual descriptions to fill the void of their blindness. It typically results from bilateral damage to the occipital lobes (visual cortex), often due to a posterior cerebral artery (PCA) stroke. **Analysis of Incorrect Options:** * **A. Wernicke's Encephalopathy:** This is an acute neurological emergency due to Thiamine (B1) deficiency. The classic triad is **Ophthalmoplegia** (usually 6th nerve palsy/nystagmus), **Ataxia**, and **Confusion**. While it involves eye signs, it does not cause cortical blindness or denial of vision. * **D. Korsakoff Syndrome:** This is the chronic phase of Thiamine deficiency. While it is famous for **confabulation** and anterograde amnesia, it does not involve cortical blindness. Patients confabulate to cover memory gaps, not visual loss. * **C. Psychogenic Amnesia:** This is a dissociative disorder characterized by a sudden retrograde loss of personal memory (autobiographical information), usually following severe stress. It does not have an organic basis like cortical blindness. **High-Yield Clinical Pearls for NEET-PG:** * **Anton Syndrome:** Cortical blindness + Anosognosia + Confabulation (Lesion: Bilateral Occipital Lobe). * **Capgras Syndrome:** The delusion that a familiar person has been replaced by an identical-looking impostor. * **Fregoli Syndrome:** The delusion that different people are actually a single person in disguise. * **Charles Bonnet Syndrome:** Visual hallucinations occurring in patients with significant visual impairment (but they have insight that the hallucinations aren't real).

Question 1

IQ related genes have recently been found on which chromosome?

Accepted Answer

Chromosome X

Answer

Chromosome 21

Answer

Chromosome 10

Answer

Chromosome 18

Question 2

Memory impairment is most likely to occur in which condition?

Accepted Answer

Down Syndrome

Answer

Alkaptonuria

Answer

Attention deficit disorder

Answer

Conduct disorder

Question 3

Increased suicidal tendency is associated with which of the following neurotransmitters?

Accepted Answer

Serotonin

Answer

Noradrenaline

Answer

Dopamine

Answer

GABA

Question 4

Maximum heritability is seen in which of the following conditions?

Accepted Answer

Schizophrenia

Answer

Depression

Answer

Mania

Answer

Panic Disorder

Question 5

Which psychological disorder is most commonly associated with myxedema?

Accepted Answer

Depression

Answer

Mania

Answer

Phobia

Answer

Paranoia

Question 6

Which of the following brain areas is less likely to play a role in depressive disorder?

Accepted Answer

Corpus callosum

Answer

Amygdala

Answer

Hippocampus

Answer

Anterior cingulate cortex

Question 7

Which of the following substances is considered an anxiolytic?

Accepted Answer

Neuropeptide Y

Answer

Caffeine

Answer

Cholecystokinin

Answer

Carbon dioxide

Question 8

Which chromosomal abnormality is associated with tall stature and aggressive or criminal behavior?

Accepted Answer

XYY

Answer

XXY

Answer

XXXY

Answer

XXYY

Question 9

Stimulation of which of the following nerves causes an elevation in mood?

Accepted Answer

Vagus Nerve

Answer

Olfactory Nerve

Answer

Optic Nerve

Answer

Trigeminal Nerve

Question 10

Cortical blindness with confabulation is seen in?

Accepted Answer

Anton syndrome

Answer

Wernicke's Encephalopathy

Answer

Psychogenic amnesia

Answer

Korsakoff syndrome

Neurobiology and Genetics of Mental Disorders — MCQs

Neurobiology and Genetics of Mental Disorders — MCQs

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