Answer it
Reading File
These are biochemistry/nutrition exam questions (Group B). The instruction says to answer any four from questions 8–12, with 13 & 14 being compulsory. I'll answer all of them comprehensively.
Group B — Complete Answers
Q8. Define gene, genome and chromosome. Classify genetic disorders with examples. (3+2)
Gene: A gene is the basic unit of heredity — a specific sequence of DNA (or RNA in some viruses) that encodes the information needed to synthesize a functional product (protein or functional RNA). It occupies a specific locus on a chromosome.
Genome: The genome is the complete set of genetic material (all DNA) of an organism, including all genes and non-coding sequences. The human genome contains ~3 billion base pairs across 23 pairs of chromosomes.
Chromosome: A chromosome is a thread-like, highly organized structure of DNA wound around histone proteins (chromatin), located in the cell nucleus. Humans have 46 chromosomes (23 pairs): 22 pairs of autosomes + 1 pair of sex chromosomes (XX or XY).
Classification of Genetic Disorders:
| Type | Mechanism | Example |
|---|---|---|
| Chromosomal disorders | Abnormal number or structure of chromosomes | Down syndrome (Trisomy 21), Turner syndrome (45,X) |
| Single-gene (Mendelian) disorders | Mutation in a single gene | Sickle cell anemia (AR), Huntington's disease (AD), Hemophilia (X-linked) |
| Multifactorial disorders | Multiple genes + environment | Diabetes mellitus, hypertension, cleft palate |
| Mitochondrial disorders | Mutations in mitochondrial DNA | Leber's hereditary optic neuropathy (LHON) |
Q9. What is RNA? Name the different types of RNA with their functions. (2+3)
RNA (Ribonucleic Acid): RNA is a single-stranded polynucleotide made of ribonucleotides (adenine, guanine, cytosine, uracil) linked by 3'→5' phosphodiester bonds. It is formed by transcription from a DNA template and plays central roles in gene expression.
Types of RNA and Functions:
| Type | Full Name | Function |
|---|---|---|
| mRNA | Messenger RNA | Carries genetic code from nucleus to ribosomes; template for protein synthesis |
| tRNA | Transfer RNA | Carries specific amino acids to the ribosome; has anticodon to match mRNA codon (adaptor molecule) |
| rRNA | Ribosomal RNA | Structural and catalytic component of ribosomes; forms the peptidyl transferase center |
| hnRNA | Heterogeneous nuclear RNA | Primary transcript (pre-mRNA) before processing |
| snRNA | Small nuclear RNA | Component of spliceosomes; involved in splicing of introns |
| miRNA / siRNA | Micro / small interfering RNA | Post-transcriptional gene regulation; RNA interference (RNAi) |
Q10. Define replication and transcription. Write the differences between replication and transcription. Write the post-transcriptional modifications. (2+1.5+1.5)
DNA Replication: The process by which a DNA molecule is copied to produce two identical daughter DNA molecules. It is semi-conservative (each new molecule has one old strand and one new strand). Occurs in S-phase of the cell cycle.
Transcription: The process by which the genetic information in one strand of DNA (template strand) is copied into a complementary RNA strand using RNA polymerase. Occurs in the nucleus; product is mRNA (or other RNA species).
Differences Between Replication and Transcription:
| Feature | Replication | Transcription |
|---|---|---|
| Template | Both strands of DNA | Only one strand (template/antisense strand) |
| Product | Two daughter DNA molecules | RNA (mRNA, tRNA, rRNA, etc.) |
| Enzyme | DNA polymerase | RNA polymerase |
| Nucleotides | Deoxyribonucleotides | Ribonucleotides |
| Primer needed | Yes (RNA primer) | No primer needed |
| Purpose | Cell division / heredity | Protein synthesis |
| Occurs | Once per cell cycle | Multiple times as needed |
Post-Transcriptional Modifications (of pre-mRNA → mature mRNA):
- 5' Capping: Addition of 7-methylguanosine cap at the 5' end → protects mRNA from degradation and aids ribosome binding
- 3' Polyadenylation: Addition of a poly-A tail (~200 adenine residues) at the 3' end → increases stability and aids nuclear export
- Splicing: Removal of non-coding introns and joining of exons by the spliceosome complex (snRNAs)
Q11. Name the proximate principles of food. What is dietary fiber? Write down the importance of dietary fiber. (1.5+1.5+2)
Proximate Principles of Food (the major nutrients):
- Carbohydrates
- Proteins
- Fats (Lipids)
- Water
- Vitamins
- Minerals
(Some classifications include dietary fiber as a 7th component)
Dietary Fiber: Dietary fiber consists of plant-derived polysaccharides and lignin that are resistant to digestion and absorption in the small intestine. They are fermented partially or completely in the large intestine.
- Soluble fiber: Pectin, guar gum, beta-glucan (found in oats, legumes, fruits)
- Insoluble fiber: Cellulose, hemicellulose, lignin (found in wheat bran, vegetables)
Importance of Dietary Fiber:
| Function | Details |
|---|---|
| Bowel regularity | Increases stool bulk, reduces transit time → prevents constipation |
| Prevents diverticular disease | Reduces pressure within the colon |
| Lowers blood cholesterol | Soluble fiber binds bile acids → reduces LDL (prevents cardiovascular disease) |
| Glycemic control | Slows glucose absorption → prevents spikes in blood sugar; helps in Type 2 diabetes |
| Prevents colorectal cancer | Dilutes carcinogens, reduces transit time in colon |
| Satiety and weight control | Increases fullness, reduces caloric intake |
| Prebiotic effect | Fermented by gut bacteria → produces short-chain fatty acids (SCFAs); nourishes colonocytes |
Recommended intake: 25–38 g/day for adults.
Q12. What is biological cloning? Difference between Biological cloning and PCR. State the application of PCR. (1+2+2)
Biological Cloning: Biological cloning is the process of producing genetically identical copies of a DNA fragment (gene cloning), cell, or organism using biological vectors (plasmids, bacteriophages) and host cells (usually bacteria like E. coli). The gene of interest is inserted into a vector, introduced into a host cell, and amplified as the host reproduces.
Differences Between Biological Cloning and PCR:
| Feature | Biological Cloning | PCR (Polymerase Chain Reaction) |
|---|---|---|
| Principle | Uses living host cells (bacteria) to amplify DNA | Cell-free, in vitro enzymatic amplification |
| Requirement | Vector + host cell + restriction enzymes + ligase | Primers + Taq polymerase + thermocycler |
| Time | Days to weeks | Hours |
| Scale | Large quantities; can express proteins | Amplifies specific DNA segments only |
| Fidelity | High | High (with proofreading polymerases) |
| Application | Protein production, gene libraries | Diagnosis, sequencing, forensics |
Applications of PCR:
- Diagnosis of infections — detection of HIV, TB, COVID-19, hepatitis viruses by amplifying pathogen DNA/RNA
- Genetic disease diagnosis — prenatal diagnosis of sickle cell anemia, thalassemia, cystic fibrosis
- Forensic medicine — DNA fingerprinting from blood, semen, hair
- Paternity testing
- Cancer diagnosis — detection of oncogenes, gene mutations (e.g., BRCA1/2)
- Sequencing — preparation for DNA sequencing (including Human Genome Project)
- Cloning — amplification of gene of interest before cloning
Q13. A 3-year-old baby admitted to hospital with puffy face, hair changes, distended abdomen and leg edema. Body weight is 70% of normal. (2+3)
a. What is your diagnosis?
The clinical picture — puffy face, hair changes (depigmentation, easily pluckable), distended abdomen (ascites), pitting edema of legs, body weight 70% of normal in a 3-year-old child — is classic for:
Kwashiorkor (Protein-Energy Malnutrition, protein-deficient type)
Key distinguishing features from marasmus:
- Edema is the hallmark (due to hypoalbuminemia → reduced oncotic pressure)
- Weight 60–80% of normal (vs. <60% in marasmus)
- "Flaky paint" dermatosis, "flag sign" in hair (alternating light/dark bands due to protein deficiency periods)
b. Biochemical tests to suggest:
| Test | Expected Finding | Rationale |
|---|---|---|
| Serum albumin | Low (<2.8 g/dL) | Primary indicator of protein deficiency |
| Serum total protein | Low | Reflects overall protein status |
| Serum transferrin | Low | Sensitive marker of protein malnutrition |
| Complete Blood Count (CBC) | Anemia (normocytic or microcytic) | Iron/protein deficiency |
| Blood glucose | Hypoglycemia | Reduced gluconeogenesis |
| Serum electrolytes | Hypokalemia, hyponatremia | Electrolyte imbalance |
| Liver function tests (LFTs) | Elevated SGOT/SGPT; fatty liver | Hepatic involvement in kwashiorkor |
| Urinary urea/creatinine ratio | Low | Reflects poor protein intake |
| Serum retinol-binding protein | Low | Short-half-life protein, very sensitive |
Q14. (Option 1 — DRI, SDA, Nutritional Assessment of Female Medical Student) (1+1.5+1.5+2+4)
What is DRI?
DRI (Dietary Reference Intakes) is a set of evidence-based reference values for nutrient intake used to plan and assess diets for healthy individuals. It includes:
| Component | Definition |
|---|---|
| EAR (Estimated Average Requirement) | Intake that meets the needs of 50% of healthy individuals |
| RDA (Recommended Dietary Allowance) | Intake that meets the needs of 97–98% of healthy individuals (EAR × 1.2) |
| AI (Adequate Intake) | Used when EAR/RDA cannot be determined; based on observed intake |
| UL (Tolerable Upper Intake Level) | Maximum intake unlikely to cause adverse effects |
SDA of Different Types of Food:
SDA (Specific Dynamic Action), also called Thermic Effect of Food (TEF), is the extra heat produced by the body during digestion, absorption, and metabolism of food.
| Food Type | SDA |
|---|---|
| Protein | 20–30% of calories consumed |
| Carbohydrate | 5–10% of calories consumed |
| Fat | 2–5% of calories consumed |
| Mixed diet | ~10% of total caloric intake |
Nutritional Status Assessment of a Female Medical Student:
Methods used:
- Dietary assessment — 24-hour dietary recall, food frequency questionnaire
- Anthropometric measurements:
- Height, weight → BMI = Weight(kg)/Height(m²)
- Normal BMI: 18.5–24.9 kg/m²
- Mid-upper arm circumference (MUAC), skinfold thickness (triceps, subscapular)
- Biochemical tests: Hemoglobin, serum albumin, serum ferritin, blood glucose, lipid profile
- Clinical examination: Signs of vitamin/mineral deficiency (pallor, glossitis, angular stomatitis, goiter, night blindness, etc.)
- Functional assessment: Muscle strength, cognitive function
Calculation of Daily Energy Requirement for a Female Medical Student:
Assumptions:
- Age: 20 years, Weight: 55 kg, Height: 160 cm
- Activity level: Moderately active (medical student)
Step 1 — BMR (Basal Metabolic Rate) using Harris-Benedict equation:
BMR (female) = 655 + (9.6 × W) + (1.8 × H) − (4.7 × A) BMR = 655 + (9.6 × 55) + (1.8 × 160) − (4.7 × 20) BMR = 655 + 528 + 288 − 94 = 1377 kcal/day
Step 2 — Physical Activity Factor:
Moderately active = BMR × 1.55
Total Energy = 1377 × 1.55 = ~2134 kcal/day
Step 3 — Add SDA (10% of total):
SDA = 2134 × 0.10 = ~213 kcal
Total Daily Energy Requirement ≈ 2134 kcal/day (SDA is already incorporated in activity factor calculations in most practical methods)
Macronutrient Distribution (for ~2100 kcal/day):
| Nutrient | % of Energy | Amount |
|---|---|---|
| Carbohydrates | 55–60% | ~290–315 g |
| Protein | 15% | ~79 g (or 0.8–1 g/kg = ~44–55 g) |
| Fat | 25–30% | ~58–70 g |
| Iron (female) | — | 18–29 mg/day (menstruation) |
| Calcium | — | 1000 mg/day |
All answers follow standard biochemistry and nutrition curricula as taught in medical/paramedical programs.
This is a shared conversation. Sign in to Orris to start your own chat.