What is the difference between Turner syndrome and Klinefelter syndrome?

Turner syndrome affects females with karyotype 45,X0 — one X chromosome is missing, causing 45 total chromosomes. These individuals are female but infertile with short stature. Klinefelter syndrome affects males with karyotype 47,XXY — an extra X chromosome, causing 47 total chromosomes. These individuals are male but infertile with tall stature and underdeveloped testes.

Genetics MCQ – Free RRB NTPC & Group D Biology Mock Test | TopperIQ

RRB NTPC & Group D Biology Mock Test — Genetics

Practice 25 high-quality MCQ on Genetics for RRB NTPC, RRB Group D & Railway exams. Covers Mendel's Laws, Monohybrid & Dihybrid Ratios, DNA Structure, Human Chromosomes, Chromosomal Disorders, Blood Groups, Haemophilia, Sickle Cell Anaemia, Central Dogma & Mutations — with detailed explanations, 12-min timer & instant score in English, Hindi, Bengali & Nepali.

🧬 Mendel's Laws📊 3:1 & 9:3:3:1 Ratios🔬 DNA Structure🧫 Chromosomes🩸 Blood Groups💉 Haemophilia🔴 Sickle Cell⬇️ Down Syndrome🔁 Central Dogma⚡ Mutations

📝 25 Questions⏱ 12 Minutes🌐 4 Languages✅ Free & Instant Score📄 PDF Scorecard

Genetics Mock Test

Q: What is the phenotypic ratio in a monohybrid cross (Tt × Tt)?

The phenotypic ratio is 3:1 (3 dominant : 1 recessive). The genotypic ratio is 1 TT : 2 Tt : 1 tt. This is Mendel's Law of Segregation — alleles separate during gamete formation and reunite randomly at fertilization.

Q: What is the phenotypic ratio in a dihybrid cross (AaBb × AaBb)?

The phenotypic ratio is 9:3:3:1. This means 9 show both dominant traits, 3 show first dominant only, 3 show second dominant only, and 1 shows both recessive traits. This demonstrates Mendel's Law of Independent Assortment.

Q: What causes Down syndrome?

Down syndrome is caused by trisomy of chromosome 21 — the person has 3 copies of chromosome 21 instead of 2, giving a total of 47 chromosomes. It results from non-disjunction during meiosis and is the most common chromosomal disorder in humans.

Q: आनुवंशिकी से RRB NTPC और Group D में कौन से प्रश्न सबसे ज्यादा पूछे जाते हैं?

सबसे ज्यादा पूछे जाने वाले टॉपिक: मेंडल के नियम (3:1 और 9:3:3:1 अनुपात), मानव गुणसूत्र (46 = 23 जोड़े), डीएनए की संरचना (वॉटसन और क्रिक, 1953), डाउन सिंड्रोम (ट्राइसोमी 21), हीमोफिलिया (X-सहलग्न), ABO रक्त समूह, अर्धसूत्री विभाजन, केंद्रीय सिद्धांत (DNA → RNA → प्रोटीन)।

Q: জিনতত্ত্ব থেকে RRB NTPC-তে কোন প্রশ্নগুলো সবচেয়ে বেশি আসে?

সবচেয়ে বেশি আসে: মেন্ডেলের সূত্র (3:1 ও 9:3:3:1 অনুপাত), মানব ক্রোমোসোম (46 = 23 জোড়া), ডিএনএ গঠন (ওয়াটসন ও ক্রিক, 1953), ডাউন সিনড্রোম (ট্রাইসোমি 21), হিমোফিলিয়া (X-সংযুক্ত), ABO রক্তগ্রুপ, অর্ধবিভাজন, কেন্দ্রীয় মতবাদ (DNA → RNA → প্রোটিন)।

Q: What is the Central Dogma of molecular biology?

The Central Dogma, proposed by Francis Crick in 1958, states that genetic information flows in one direction: DNA → RNA → Protein. DNA is transcribed into mRNA (transcription), and mRNA is then translated into protein (translation). This is the fundamental principle governing gene expression in all living organisms.

Q: What is semi-conservative DNA replication?

Semi-conservative replication means each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This was experimentally proved by Meselson and Stahl in 1958 using heavy nitrogen (¹⁵N) and light nitrogen (¹⁴N) isotopes in E. coli bacteria.

Biology · RRB NTPC & Group D · 25 Questions · 12 Min

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Frequently Asked Questions — Genetics & Heredity

What is the phenotypic ratio in a monohybrid cross (Tt × Tt)?

The phenotypic ratio is 3:1 — three individuals show the dominant trait for every one that shows the recessive trait. The genotypic ratio is 1 TT : 2 Tt : 1 tt. This result demonstrates Mendel's Law of Segregation, which states that alleles separate during gamete formation and come together randomly at fertilisation.

What is the phenotypic ratio in a dihybrid cross (AaBb × AaBb)?

The phenotypic ratio is 9:3:3:1 — 9 show both dominant traits, 3 show only the first dominant, 3 show only the second dominant, and 1 shows both recessive traits. This ratio proves Mendel's Law of Independent Assortment, which states that genes controlling different characters assort independently into gametes.

What causes Down syndrome and how is it different from Turner syndrome?

Down syndrome is caused by trisomy of chromosome 21 — the person has 47 chromosomes instead of 46, due to non-disjunction during meiosis. Turner syndrome (45, X0) affects females who have only one X chromosome, resulting in 45 chromosomes. Down syndrome affects both sexes, while Turner syndrome affects only females.

आनुवंशिकी से RRB NTPC और Group D में कौन से प्रश्न सबसे ज्यादा पूछे जाते हैं?

सबसे ज्यादा पूछे जाने वाले टॉपिक: मेंडल के नियम (3:1 और 9:3:3:1 अनुपात), मानव गुणसूत्र (46 = 23 जोड़े), डीएनए की संरचना (वॉटसन और क्रिक, 1953), डाउन सिंड्रोम (ट्राइसोमी 21), टर्नर सिंड्रोम (45, X0), हीमोफिलिया (X-सहलग्न अप्रभावी), ABO रक्त समूह, केंद्रीय सिद्धांत (DNA → RNA → प्रोटीन)।

জিনতত্ত্ব থেকে RRB NTPC-তে কোন প্রশ্নগুলো সবচেয়ে বেশি আসে?

সবচেয়ে বেশি আসে: মেন্ডেলের সূত্র (3:1 ও 9:3:3:1 অনুপাত), মানব ক্রোমোসোম (46 = 23 জোড়া), ডিএনএ গঠন (ওয়াটসন ও ক্রিক, 1953), ডাউন সিনড্রোম (ট্রাইসোমি 21), টার্নার সিনড্রোম (45, X0), হিমোফিলিয়া (X-সংযুক্ত প্রচ্ছন্ন), ABO রক্তগ্রুপ, কেন্দ্রীয় মতবাদ (DNA → RNA → প্রোটিন)।

What is semi-conservative DNA replication?

Semi-conservative replication means that each new DNA double helix consists of one original (parental) strand and one newly synthesised strand. This was experimentally proved by Meselson and Stahl in 1958 using heavy nitrogen (¹⁵N) and light nitrogen (¹⁴N) isotopes in E. coli. The name "semi-conservative" indicates that half of the original molecule is conserved in each daughter molecule.

What is the Central Dogma of molecular biology?

The Central Dogma, proposed by Francis Crick in 1958, states that genetic information flows in one direction: DNA → RNA → Protein. The first step, where DNA is copied into messenger RNA, is called transcription. The second step, where mRNA is decoded by ribosomes to build a protein chain, is called translation. This principle governs gene expression in virtually all living organisms.