Original revision introduction and starter practice. Full learning texts are available through the publisher links below. This guide is not a CBSE-issued solution manual.
Revision introduction
In Mendelian inheritance, alleles segregate during gamete formation. A monohybrid cross of heterozygotes gives a 1:2:1 genotype ratio and, under complete dominance, a 3:1 phenotype ratio. These assumptions matter: incomplete dominance and codominance change the phenotype ratio.
Curriculum navigation
Sexual Reproduction in Flowering Plants
Human Reproduction
Reproductive Health
Principles of Inheritance and Variation
Molecular Basis of Inheritance
Evolution
Human Health and Disease
Microbes in Human Welfare
Biotechnology – Principles and Processes
Biotechnology and its Applications
Organisms and Populations
Ecosystem
Biodiversity and Conservation
Consult the current official syllabus for examinable sections, project-only content, practicals, prescribed texts and exclusions. A unit index does not override those boundaries.
Original practice
What is the genotype ratio for Aa×Aa?
1 AA:2 Aa:1 aa
3 AA:1 aa
All Aa
All AA
Worked answer
1 AA:2 Aa:1 aa
The four equally likely combinations are AA, Aa, aA and aa.
Full publisher materials and answer resources
CBSE 12 Biology · syllabus · CBSE · 2026-27 The current official syllabus defines examinable content, internal assessment, practicals and prescribed books. Unit names in the app are a navigation index; consult this document for exclusions and assessment boundaries.
NCERT · Biology · NCERT · 2026-27 Official book selector with chapter PDFs and complete-book download. A textbook may contain material outside the assessed syllabus; follow the linked current syllabus.
NCERT Exemplar Problems and Answers · NCERT · Archive · map to 2026-27 Select Class 12 and the subject. The official portal includes answer sections. Older exemplars require checking each question against the current syllabus.
KVS student support material · Class 12 · Kendriya Vidyalaya Sangathan · 2026-27 Use the 2026–27 support-material folders linked by the school. These are KVS teaching/revision resources, not CBSE official marking schemes. Subject availability varies; older packs must be mapped to the current syllabus.
CBSE 2026–27 · Sample question paper · CBSE · 2026-27 Official document listed by CBSE for 2026–27. Open at the publisher; no third-party solutions are represented as official. Sample papers are practice models, not previous board examination papers.
CBSE 2026–27 · Official marking scheme / answer key · CBSE · 2026-27 Official document listed by CBSE for 2026–27. Open at the publisher; no third-party solutions are represented as official. Sample papers are practice models, not previous board examination papers.
NCERT laboratory manuals · NCERT · Reference · map to 2026-27 Select the class and subject. Use the practical list in the current CBSE syllabus; experiments require teacher supervision.
DIKSHA · curriculum learning resources · Ministry of Education / DIKSHA · Current portal Choose CBSE/NCERT, Class 12, subject and medium. This is a searchable portal, not a promise of a specific playable lesson.