Answers :
1️⃣ Answer: F1 hybrids showed only the dominant trait 🌱
🧠 Explanation: In Mendel’s experiments (monohybrid cross) the dominant allele masks the recessive in F1, so all F1 display the dominant phenotype. 🔬 Key fact: F1 reveals dominance — useful for Class 10 Biology, CBSE. 🧬
2️⃣ Answer: Law of Segregation ⚖️
🧠 Explanation: Mendel’s Law of Segregation states allele pairs separate during gamete formation so each gamete carries one allele; this explains monohybrid ratios. 🔬 Tip: Use this to predict genotypes in test crosses (Class 10, CBSE). 🧬
3️⃣ Answer: False ❌
🧠 Explanation: Mendel’s law of independent assortment does NOT always apply to genes on the same chromosome — linkage can change ratios. 🔬 Exam note: Linkage breaks the independent 9:3:3:1 expectation (Mendel’s experiments, CBSE). 🧬
4️⃣ Answer: Dominant allele 🏆
🧠 Explanation: A dominant allele masks the effect of a recessive allele in heterozygotes, seen clearly in Mendel’s monohybrid crosses. 🔬 Quick fact: Dominant phenotype appears in heterozygous F1 (Class 10 Biology). 🌱
5️⃣ Answer: Phenotype 👀
🧠 Explanation: Phenotype is the observable trait (e.g., flower color) produced by genotype; Mendel recorded phenotypes to infer inheritance. 🔬 Exam tip: Always distinguish phenotype vs genotype in answers (CBSE). 🧬
6️⃣ Answer: Test cross with homozygous recessive 🔬
🧠 Explanation: A test cross (unknown × homozygous recessive) reveals whether the unknown is homozygous or heterozygous by F1 ratios. 🔍 Tip: Use test cross to confirm genotype — classic in Mendel’s experiments (Class 10). 🌱
7️⃣ Answer: 3:1 (dominant:recessive) 📊
🧠 Explanation: Mendel observed a 3:1 phenotypic ratio in F2 of monohybrid crosses when one allele is dominant and the other recessive. 🔬 Remember: 3 dominant : 1 recessive is a monohybrid signature (CBSE). 🧬
8️⃣ Answer: True ✅
🧠 Explanation: A dihybrid cross follows inheritance of two traits simultaneously (e.g., seed shape & color) as Mendel showed in his experiments. 🔬 Exam note: Use dihybrid Punnett squares to predict 9:3:3:1 (Class 10 Biology). 🌱
9️⃣ Answer: 9:3:3:1 (dihybrid F2) 🔢
🧠 Explanation: For two independently assorting traits Mendel found a 9:3:3:1 phenotypic ratio in F2 of dihybrid crosses. 🔬 Tip: This ratio signals independent assortment in Mendel’s experiments (CBSE). 🧬
10️⃣ Answer: Particulate inheritance 🧩
🧠 Explanation: Mendel’s work supports particulate inheritance — hereditary units (genes) remain discrete and aren’t blended across generations. 🔬 Quick fact: This concept contrasts with blending inheritance (Class 10, CBSE). 🌱
11️⃣ Answer: Parental generation (P) 👪
🧠 Explanation: P denotes the original parents used by Mendel to start crosses; their chosen traits set the experiment’s baseline. 🔬 Exam tip: Always label P, F1, F2 clearly in diagrams (Mendel’s experiments). 🧬
12️⃣ Answer: True ✅
🧠 Explanation: F1 is produced by crossing two P individuals; Mendel used this to study trait dominance in the first filial generation. 🔬 Quick tip: F1 phenotype shows dominance patterns (Class 10 Biology, CBSE). 🌱
13️⃣ Answer: 1:2:1 (genotypic ratio) 🔬
🧠 Explanation: A heterozygote × heterozygote monohybrid cross yields genotypes in 1:2:1 (AA:Aa:aa) in F2, matching Mendel’s segregation law. 🔍 Remember: Genotype vs phenotype ratios differ (CBSE exam point). 🧬
14️⃣ Answer: True ⚠️
🧠 Explanation: If genes are closely linked on the same chromosome, independent assortment may fail and the expected 9:3:3:1 ratio may not appear. 🔬 Exam hint: Linkage reduces recombinant types — test for altered ratios (Class 10). 🌱
15️⃣ Answer: Study distinct, single-gene traits with clear alternatives ✅
🧠 Explanation: Mendel chose simple, contrasting traits (e.g., round vs wrinkled) to get clear ratios and reliable Mendelian patterns. 🔬 Key point: Pick single-gene traits in experimental design — great tip for CBSE-style questions. 🧬
📚 Topics Covered
📘 What this summary covers — at a glance ✅
Compact Class 10 Biology summary on Mendel’s experiments (monohybrid and dihybrid cross) for CBSE — concise theory, 15 practice questions, key ratios and exam-ready tips to master inheritance concepts.
🧠 Core concepts — succinct explanations
- Law of Dominance — In a monohybrid cross the dominant allele masks the recessive in the F1; useful for predicting F1 phenotype (Class 10 Biology, CBSE).
- Law of Segregation — Allele pairs separate during gamete formation so each gamete carries one allele, explaining 1:2:1 genotypic ratios in F2.
- Law of Independent Assortment — Alleles of different genes assort independently when on different chromosomes, producing the 9:3:3:1 dihybrid ratio for unlinked genes.
- Test cross — Cross with a homozygous recessive to reveal an unknown genotype; key practical method in Mendel’s experiments.
- Particulate inheritance — Traits are inherited as discrete units (genes), not by blending — core idea behind Mendel’s findings for inheritance patterns.
⚡ Important features to remember (Quick facts)
- Monohybrid F2 phenotypic ratio = 3:1 (dominant : recessive).
- Monohybrid F2 genotypic ratio = 1:2:1 (AA : Aa : aa).
- Dihybrid F2 phenotypic ratio (unlinked) = 9:3:3:1.
- F1 shows dominance; F2 reveals segregation and ratios.
- Linkage can alter expected Mendelian ratios (genes close on same chromosome).
- Mendel’s peas: clear contrasting traits (single-gene) gave reproducible ratios — why his design worked.
✅ Revision checklist & exam tips
- ✓ Write P, F1, F2 labels clearly on diagrams.
- ✓ Distinguish phenotype (observable) vs genotype (genetic makeup).
- ✓ For monohybrid: set up Punnett square for Aa × Aa or test cross as needed.
- ✓ For dihybrid: use fork method or 4×4 Punnett square to get 9:3:3:1.
- ✓ State assumptions (e.g., independent assortment, no linkage) when answering ratio questions.
- ✓ Use correct notation (A, a) and count gametes systematically for calculations.
- Exam tip 1: When asked for ratios, show working (Punnett square or allele list) to earn method marks.
- Exam tip 2: If linkage is mentioned, explain why 9:3:3:1 may not apply — mention recombination briefly.
- Exam tip 3: Use clear, labeled diagrams for crosses and state the conclusion in one sentence.
- Exam tip 4: Memorize key ratios (3:1, 1:2:1, 9:3:3:1) and apply them quickly in Class 10 CBSE questions.
🗂️ Key terms (glossary)
- Allele — Alternative form of a gene (A or a; exam: allele pair determines trait).
- Phenotype — Observable trait (e.g., purple flowers; what you see).
- Genotype — Genetic constitution (e.g., AA, Aa, aa; exam: use to predict offspring).
- Homozygous — Two identical alleles (AA or aa; “pure” breed).
- Heterozygous — Two different alleles (Aa; shows dominant phenotype).
- Monohybrid cross — Cross studying one trait (exam focus: 3:1 ratio in F2).
- Dihybrid cross — Cross studying two traits simultaneously (exam focus: 9:3:3:1 if unlinked).
- Test cross — Cross with homozygous recessive to determine unknown genotype.
- Independent assortment — Genes on different chromosomes assort independently (leads to 9:3:3:1).
- Linkage — Genes close on same chromosome that may be inherited together (affects expected ratios).
- Particulate inheritance — Concept that genes are discrete units, not blended (Mendel’s key conclusion).