BZYCT-137 Solved Question Paper June 2026 gives a complete written answer to all 7 questions of the IGNOU Genetics and Evolutionary Biology term-end paper, which carried 50 marks over 2 hours. Two answers are open on this page — Q3 on epistasis and Q4 on Lamarckism; the other five come in the full file on WhatsApp 9899436384.
BZYCT-137 Genetics and Evolutionary Biology key facts for the June 2026 solved question paper
- Course code: BZYCT-137 — but note that the June 2026 title line misprints it as BZYCT-131, while the header and footer of every page read BZYCT-137. It is a printing slip, not a different paper
- Course title: Genetics and Evolutionary Biology
- Programmes: Bachelor of Science (General), BSCG; also B.Sc. Multidisciplinary, BSCM
- Credits: 4, theory; taken with its 2-credit companion lab BZYCL-138, so the pair comes to 6 credits
- Blocks and units: 4 blocks, 16 units — two genetics blocks (Units 1 to 9) and two evolution blocks (Units 10 to 16)
- Maximum marks: 50 (Term-End Examination)
- Duration: 2 hours
- Structure of the June 2026 paper: Question 1 compulsory for 10 marks, then any four of Questions 2 to 7 at 10 marks each
- Answerable pieces: 7 questions, which break into 19 separately written pieces once you count Q1's ten items and the two-part questions
- Mark values used: 1, 2, 5, 8 and 10 — Question 3's 2 + 8 is the most lopsided split we have seen on an IGNOU paper
- Weightage in the final result: term-end exam 70 per cent, tutor-marked assignment 30 per cent
- Samples shown on this page: 2 (Q3 epistasis, Q4 Lamarckism)
- Questions in the paid file: all 7 answered; 5 are not shown on this page
What the BZYCT-137 solved question paper June 2026 covers
BZYCT-137 is the 4-credit zoology core theory course of IGNOU's Bachelor of Science (General), studied alongside the lab course BZYCL-138. It runs from Mendelian inheritance and chromosome abnormalities to Lamarck, Darwin, speciation and extinction.
The June 2026 paper leaned on the genetics half. Questions asked for two chromosomal sex determination mechanisms, a comparison of dominant and recessive epistasis, and the role of chloroplast and mitochondria in extra-nuclear inheritance. The evolution half tested Lamarckism, genetic repatterning, post-mating isolation, dosage compensation and homologous organs.
This paper did something no other paper on our site has done, and if you are preparing for December you need to read section 6 before anything else. The four most-repeated topics in this course — each set in five of the six earlier papers we hold — were all four absent from June 2026. Meanwhile four of its seven questions were on topics that had never once been set as full questions in those six papers. A student who revised strictly from the repeat list would have walked into an unfamiliar paper. Section 6 explains where those four new topics actually came from, and the answer is useful.
One more detail worth knowing before you compare your paper with ours. The official June 2026 paper prints "BZYCT-131" in its title line, although the header and footer on every page say BZYCT-137. BZYCT-131 is a different zoology course. It is a printing slip, and our file follows the BZYCT-137 paper exactly, question by question.
BZYCT-137 sample solved questions: epistasis and Lamarckism
Two of the seven questions are fully solved below, Q3 on epistasis and Q4 on Lamarckism. We picked these because they show both halves of the course: a genetics answer built on crosses, ratios and tables, and an evolution answer built on theory, examples and criticism. Every other answer in the file follows the same structure.
Question 3 Any 4 of Q2 to Q7 Block 1, Unit 2 2 + 8 marks tables and ratios Never set as a full question in the 6 earlier papers
3. What is epistasis? Compare the dominant and recessive epistasis giving suitable examples. 2 + 8
Part A: What is epistasis (2 marks)
Epistasis is a kind of gene interaction in which one gene masks or suppresses the expression of another, non-allelic gene. The gene that does the masking is called epistatic, and the gene whose effect is hidden is called hypostatic. William Bateson used the term in 1909.
Epistasis is not the same as dominance. Dominance works between two alleles of the same gene — T over t, say — whereas epistasis works between alleles of two different genes. Because one gene hides another, the familiar Mendelian dihybrid ratio of 9:3:3:1 is modified, and the F2 usually shows only three phenotypic classes.
Part B: Dominant epistasis, 12:3:1 (part of 8 marks)
Here a single dominant allele of one gene is enough to hide both alleles of the second gene. The classic example is fruit colour in summer squash (Cucurbita pepo). The dominant allele W gives white fruit whatever the colour gene says. Only in ww plants can the second gene show itself: Y gives yellow fruit and y gives green fruit.
When a white WWYY plant is crossed with a green wwyy plant, the F1 (WwYy) is white. Selfing the F1 gives:
| Genotype class | Proportion | Fruit colour |
|---|---|---|
| W_Y_ | 9/16 | White — W masks Y |
| W_yy | 3/16 | White — W masks y |
| wwY_ | 3/16 | Yellow |
| wwyy | 1/16 | Green |
The two white classes merge, so the ratio becomes 12 white : 3 yellow : 1 green.
Recessive epistasis, 9:3:4
Here the masking happens only when the epistatic gene is homozygous recessive. Coat colour in mice is the standard example. Gene C is needed to make any pigment, so cc mice are albino whatever the other gene carries. Gene A decides the pattern of pigment: A gives agouti, banded grey-brown hair, and a gives black.
Crossing an agouti AACC mouse with an albino aacc mouse gives an agouti F1 (AaCc). The F2 then segregates as:
| Genotype class | Proportion | Coat colour |
|---|---|---|
| A_C_ | 9/16 | Agouti |
| aaC_ | 3/16 | Black |
| A_cc | 3/16 | Albino — cc masks A |
| aacc | 1/16 | Albino |
The two albino classes merge, giving 9 agouti : 3 black : 4 albino. Coat colour in Labrador retrievers follows the same 9:3:4 pattern: ee dogs are yellow whatever the B gene carries, while B_E_ dogs are black and bbE_ dogs are chocolate.
Comparison of dominant and recessive epistasis
| Basis | Dominant epistasis | Recessive epistasis |
|---|---|---|
| Masking allele | One dominant allele (W) | Two recessive alleles (cc) |
| Genotype that masks | WW or Ww | cc only |
| Modified F2 ratio | 12:3:1 | 9:3:4 |
| Classes that merge | 9 (W_Y_) and 3 (W_yy) | 3 (A_cc) and 1 (aacc) |
| Example | Fruit colour in summer squash | Coat colour in mice and Labradors |
| Other name | Simple dominant epistasis | Supplementary gene interaction |
Conclusion. Both types show that genes often act in steps of one pathway. In mice, the C gene controls an early step, pigment formation, so if that step fails the A gene has nothing to work on. Epistasis therefore explains why some dihybrid crosses do not give the textbook 9:3:3:1 ratio.
Watch the 2 + 8 split, which is the most lopsided on the paper. Two marks is about 60 words — the definition, the epistatic-and-hypostatic pair, and one line distinguishing epistasis from dominance. Everything else belongs to the eight-mark half, and in that half the two F2 tables are the marks. An examiner looking for 12:3:1 and 9:3:4 wants to see which classes merged and why; a candidate who states the ratios without the working gets part credit at best. Draw both tables first, then write around them.
Question 4 Any 4 of Q2 to Q7 Block 3, Unit 11 10 marks theory + criticism Classical Lamarckism never set before; Neo-Lamarckism twice
4. Explain Lamarckism and discuss the different assumptions proposed. 10
Introduction. Lamarckism is the theory of evolution put forward by the French naturalist Jean-Baptiste de Lamarck (1744 to 1829) in his book Philosophie Zoologique (1809). It is also called the theory of inheritance of acquired characters. Lamarck was among the first to argue clearly that species are not fixed but change slowly over long periods.
His central idea was simple: organisms change during their own lifetime in response to the environment, and these changes are passed on to their offspring. Over many generations the small changes add up, and a new species appears.
Assumptions of Lamarckism
- Internal vital force. Living organisms and their parts have an inborn tendency to grow larger and more complex. Lamarck saw this as a natural drive towards greater perfection.
- Effect of environment and new needs. A change in surroundings creates new needs. The animal changes its habits to meet them, and the new habit leads to a new structure or a change in an old one. This inner want is sometimes called appetency.
- Use and disuse of organs. An organ that is used constantly becomes stronger and larger, while an organ that is not used becomes weak and slowly disappears.
- Inheritance of acquired characters. The changes an organism acquires through use or disuse during its life are transmitted to the next generation. Repeated over generations, they produce a new species.
| Example | Lamarck's explanation | Assumption used |
|---|---|---|
| Long neck of the giraffe | Ancestors stretched neck and forelimbs to reach leaves on tall trees; the stretch was inherited | New needs, use, inheritance |
| Limbless snakes | Ancestors crawled through narrow spaces, stopped using legs, and the legs were lost | Disuse, inheritance |
| Webbed feet of ducks | Spreading the toes while swimming stretched the skin between them | Use, inheritance |
| Small wings of flightless birds | Birds such as the ostrich stopped flying, so the wings shrank | Disuse, inheritance |
Criticism of Lamarckism. August Weismann tested the inheritance of acquired characters by cutting off the tails of mice and breeding them for five generations. None of the 901 young mice was born with a shorter tail. He concluded that changes to body cells, the somatoplasm, are not passed on; only changes in the germ cells, the germplasm, are inherited.
Everyday evidence agrees. Pierced ears and noses are not inherited, and a blacksmith's strong arm muscles do not pass to his children. The idea that a need can create a new organ also has no experimental support.
Significance. Even though its mechanism was rejected, Lamarckism was the first organised theory of evolution. It stressed the role of the environment and the idea of gradual change, which prepared the ground for Darwin. Later workers revived some of its ideas as Neo-Lamarckism, but modern genetics does not support the inheritance of characters acquired through use and disuse.
The question asks you to "explain Lamarckism and discuss the assumptions", so the four numbered assumptions are the spine of the answer and the examples are evidence for them — label each example with the assumption it illustrates, as the table does. The two details hardest for an examiner to ignore are Philosophie Zoologique, 1809 and Weismann's 901 mice over five generations. If you are short of time, drop two examples before you drop either of those.
Questions answered only in the full file
The five questions below are listed exactly as printed in the official paper. Their answers, including the Q1 definitions and matching set, are only in the full file.
1. (I) Define the following terms: 5 × 1 = 5
(i) Phenotype (ii) Chromosomal aberration (iii) Diandry (iv) Vestigial organs (v) Sympatric speciation1. (II) Match the following: 5 × 1 = 5
Column A: (i) Codominance (ii) Barbara McClintock (iii) Morgan (iv) Mechanical isolation (v) Incomplete dominance
Column B: (a) Sex limited [sex linked] inheritance (b) Potential mates meet and mate but no transfer of sperm (c) Pink flowers of Mirabilis jalapa (d) MN blood group of humans (e) Transposable elements2. Describe any two types of chromosomal sex determination mechanisms giving suitable examples. 10
5. Discuss the involvement of chloroplast and mitochondria in extra-nuclear inheritance. 10
6. (a) Elaborate the concept of genetic repatterning during isolation. 5
(b) Describe the different types of postmating isolating mechanisms giving suitable examples. 57. Write short notes on the following: 2 × 5 = 10
(a) Dosage compensation (b) Homologous organs
A note on the matching set. Column B item (a) is printed as "Sex limited inheritance", but the pairing it is clearly meant for is Morgan, whose famous work was on sex-linked inheritance — the white-eyed Drosophila crosses. Sex-limited inheritance is a different concept and is not particularly associated with Morgan. The four other pairings fix (a) to Morgan by elimination, so answer it as the examiner intends and, if you have room, add the words "sex-linked, as in Morgan's white-eye Drosophila work" to show you know which is which.
BZYCT-137 block and unit wise syllabus
BZYCT-137 is split into 4 blocks and 16 units: two genetics blocks (Units 1 to 9) and two evolution blocks (Units 10 to 16).
| Block | Units in the block | Key topics examined | June 2026 |
|---|---|---|---|
| Block 1: Heredity and Phenotype | 1 Introduction to Genetics; 2 Extension and Modifications of Mendelian Genetic Analysis-I; 3 Linkage, Crossing-Over and Chromosome Mapping; 4 Extra-Nuclear Inheritance | Mendel's laws, epistasis and multiple alleles, chromosome mapping, chloroplast and mitochondrial inheritance | Q3 (Unit 2), Q5 (Unit 4); Unit 3 not asked |
| Block 2: The Physical Basis of Heredity | 5 Structural Abnormalities in Chromosomes; 6 Numerical Abnormalities in Chromosomes; 7 Sex Determination; 8 The Nature and Structure of Genetic Material; 9 Mutations and Mutagenesis | Inversions and translocations, trisomy and polyploidy, XX-XY and ZW-ZZ systems, DNA structure, mutagens | Q2 and Q7(a) (Unit 7); Units 6, 8 and 9 not asked |
| Block 3: Evolution: Concept, Evidence and Mechanisms | 10 Major Events in History of Life; 11 Introduction of Evolutionary Theories; 12 Evolutionary Evidences; 13 Evolutionary Change: Natural Selection | Origin of life, Lamarckism and Darwinism, homologous organs and fossils, industrial melanism | Q4 (Unit 11), Q7(b) (Unit 12); Units 10 and 13 not asked |
| Block 4: Speciation and Species Extinction | 14 Species Concept and Speciation-I; 15 Species Concept and Speciation-II; 16 Species Extinction | Species concepts, isolating mechanisms, allopatric and sympatric speciation, mass extinction | Q6 (Units 14 and 15); Unit 16 not asked |
June 2026 drew its questions from 9 of the 16 units — among the narrowest coverage we have measured · the seven that fed nothing are Units 3, 6, 8, 9, 10, 13 and 16 · the genetics half supplied three full questions and the evolution half two, with Question 7 taking one note from each
Neither half of the course could answer this paper on its own, and Question 7 is why. You need four of Questions 2 to 7. Genetics gives you Q2, Q3 and Q5 — three. Evolution gives you Q4 and Q6 — two. Question 7 would be the fourth for either, except that its two compulsory notes come from opposite halves: dosage compensation from Unit 7 in genetics, homologous organs from Unit 12 in evolution. So whichever half you prepared, Question 7 forces you into the other.
That is a deliberate-looking piece of paper design, and it is the opposite of what the sibling course BZYCT-133 did in the same session, where comparative anatomy alone could complete the paper. On BZYCT-137 there was no safe single half.
Students who use the BZYCT-137 study material block by block will notice that sex determination (Unit 7) carried both a full 10-mark question and one of the Q7 notes, and that extra-nuclear inheritance (Unit 4) carried a full 10-mark question of its own.
BZYCT-137 question paper pattern and marks distribution
The term-end paper carries 50 marks for 2 hours: Q1 is compulsory and you attempt any four of Q2 to Q7, all worth 10 marks each.
| Question | Format in June 2026 | Marks | Choice |
|---|---|---|---|
| Q1 (I) | Five one-line definitions, from phenotype to sympatric speciation | 5 × 1 = 5 | Compulsory |
| Q1 (II) | Five-pair matching set on geneticists and isolation terms | 5 × 1 = 5 | Compulsory |
| Q2, Q4, Q5 | Single 10-mark descriptive questions | 10 each | Any four of Q2 to Q7 |
| Q3 | Definition plus comparison, split 2 + 8 | 10 | |
| Q6 | Two-part question, 5 + 5 | 10 | |
| Q7 | Two short notes, 2 × 5 | 10 |
Q1 (10) + six questions of 10 in Q2 to Q7 = 70 marks printed, 50 attempted · five distinct mark values: 1, 2, 5, 8 and 10 · Q3's 2 + 8 is the most lopsided split on any paper we have analysed · 120 minutes for 50 marks = 2.4 minutes a mark
Question 1 is the best-value ten marks on this paper, though less so than on the sibling courses. Its ten items carry a mark each, which is far more efficient than the long questions — but note that BZYCT-137 asks you to define five terms rather than fill five blanks, so each needs a line or two rather than a single word. Budget twelve to fifteen minutes, not the eight that BZYCT-135's fill-in-the-blank version needs, and give the remaining 105 minutes to your four long questions, about 26 minutes each.
On answer length, we have corrected what this page previously said. It gave 450 to 550 words for a 10-mark question and 250 for a 5-mark part, which is 50 words a mark. Four long questions at that rate is about 2,000 words in under two hours — around 17 words a minute, where a person writing by hand sustains 11 to 12, and that is before you have ruled a single genotype table. The realistic figures are:
| Part | Marks | Roughly how many words | Roughly how many minutes | Best form |
|---|---|---|---|---|
| A Q1 definition or matching pair | 1 | One line, or one pairing | 1 to 2 | Nothing added |
| The short half of Q3 | 2 | 60 | 5 | Definition and one contrast |
| A five-mark part or short note | 5 | 140 to 160 | 13 | Numbered points, or a table |
| The long half of Q3 | 8 | 230 to 250 | 21 | Two F2 tables plus a comparison table |
| A full 10-mark question | 10 | 280 to 320 | 26 | Numbered points, plus a table where it earns marks |
That is about 30 words a mark, the same figure we use on the sibling course BZYCT-135 and the same that IGNOU itself prints on its psychology papers. On a genetics paper it is if anything generous, because a filled genotype table conveys in six rows what would take a paragraph and earns the marks more directly.
The Q1 format changes from session to session, so do not learn one shape. June 2022 used true-or-false items, December 2022 used fill-in-the-blanks with a choose-the-word set, and June 2025 and June 2026 used definitions with matching. What has not changed in any paper we checked is the 50-mark, two-hour frame and the one-compulsory-plus-any-four rule. Papers from other courses in the programme are on our BSCG question paper page.
Most repeated BZYCT-137 topics, and why June 2026 broke the pattern
We counted only full descriptive questions and short notes in Q2 to Q7, not the one-mark items in Q1. The papers used were June 2022, December 2022, June 2023, December 2023, June 2024 and June 2025, from IGNOU's own sites. The December 2024 and December 2025 papers were not available to us, so they are not in the count. June 2026 sits outside the window, in its own column.
| Topic | Unit | Sessions asked (Q2 to Q7) | Papers (of 6) | In June 2026? |
|---|---|---|---|---|
| Multiple alleles, ABO and Rh blood groups | 2 | Jun 2022, Jun 2023, Dec 2023, Jun 2024, Jun 2025 | 5 | No |
| Numerical chromosome abnormalities (trisomy, polyploidy) | 6 | Jun 2022, Dec 2022, Jun 2023, Dec 2023, Jun 2024 | 5 | No |
| Extinction and mass extinction | 16 | Jun 2022, Dec 2022, Jun 2023, Dec 2023, Jun 2024 | 5 | No |
| Darwinism, Neo-Darwinism and natural selection | 13 | Jun 2022, Dec 2022, Dec 2023, Jun 2024, Jun 2025 | 5 | No |
| Homologous and analogous organs | 12 | Jun 2022, Dec 2022, Jun 2024, Jun 2025 | 4 | Yes — Q7(b) |
| Structural aberrations (inversion, translocation, deletion) | 5 | Jun 2022, Jun 2023, Dec 2023, Jun 2025 | 4 | Only as a Q1 definition |
| Mutation, mutagenesis and DNA repair | 9 | Jun 2022, Dec 2022, Jun 2024, Jun 2025 | 4 | No |
| Isolating mechanisms (pre-mating and post-mating) | 15 | Dec 2022, Jun 2023, Dec 2023 | 3 | Yes — Q6(b) |
| Allopatric and sympatric speciation | 14 | Dec 2022, Jun 2023, Jun 2024 | 3 | Only as a Q1 definition |
| Origin of life | 10 | Dec 2022, Jun 2023, Jun 2024 | 3 | No |
| Neo-Lamarckism | 11 | Jun 2022, Jun 2025 | 2 | Related — Lamarckism as Q4 |
| Extra-nuclear inheritance (chloroplast, mitochondria) | 4 | Jun 2025 | 1 | Yes — Q5 |
| Dosage compensation | 7 | Dec 2022 | 1 | Yes — Q7(a) |
13 recurring topics tracked · only 5 came back as full questions and two more appeared only as a Q1 definition · a full-question reuse rate of 38 per cent, the lowest we have measured on any course by a wide margin · and all four of the five-time topics were skipped
Read the top four rows again, because this has not happened on any other paper we have analysed. Multiple alleles, numerical chromosome abnormalities, extinction and Darwinism were each set in five of the six earlier papers. Every other course we track carries its top-count topics forward almost without exception. June 2026 left all four out.
And what it asked instead had almost no history. Setting the seven questions against the six-paper record:
| June 2026 question | Topic | Times set as a full question in the 6 earlier papers |
|---|---|---|
| Q2 | Chromosomal sex determination mechanisms | 0 |
| Q3 | Epistasis, dominant versus recessive | 0 |
| Q4 | Classical Lamarckism and its assumptions | 0 — Neo-Lamarckism twice, which is not the same question |
| Q6(a) | Genetic repatterning during isolation | 0 |
| Q5 | Extra-nuclear inheritance | 1 |
| Q7(a) | Dosage compensation | 1 |
| Q6(b) | Post-mating isolating mechanisms | 3 |
| Q7(b) | Homologous organs | 4 |
Four of the eight scored zero. A student who had revised from the repeat list alone would have found, among the six choice questions, only Q7 fully familiar.
But the four new topics were not new — they were in the assignments. Sex determination, epistasis, classical Lamarckism and genetic repatterning all appear in the BZYCT-137 tutor-marked assignments of 2022 to 2024. That is the single most useful thing on this page, because it means the pattern did not break so much as move: the assignment was predicting this paper better than the exam history was.
We have now seen the same thing on five other IGNOU courses, where a topic sitting in the current assignment turned up in the next paper. On BZYCT-137 it is the strongest case we have found, because four questions in one paper came from that source.
What to prepare for December 2026
June 2026 leaves you with two readings, and the honest answer uses both.
The first reading is that the four five-time topics are overdue. A record of five appearances in six papers is strong evidence, and one omission is one data point. The unit mapping agrees with this reading and agrees unusually well: five of the seven units that fed nothing in June 2026 are exactly the units behind five of the six skipped topics. Unit 6 is numerical abnormalities, Unit 13 is natural selection and Darwinism, Unit 16 is extinction, Unit 9 is mutation, Unit 10 is the origin of life. The sixth skipped topic, multiple alleles, sits in Unit 2 — a unit that was examined, through epistasis, so it was the multiple-alleles half that went untested. Count and unit point the same way on every one of the six.
The second reading is that the examiner has widened the net, and the newly-introduced topics are now live. Both readings can be true at once, and the practical conclusion is simple: prepare the overdue topics first, but do not drop the June 2026 ones, and read the current assignment.
The ranked list:
- Darwinism, Neo-Darwinism and natural selection (Unit 13). Five of six papers, skipped, and Unit 13 fed nothing. One of the four largest topics in the course.
- Extinction and mass extinction (Unit 16). Five of six, skipped, Unit 16 dead. Block 4's only other unit, and the whole of what Block 4 did not ask.
- Numerical chromosome abnormalities (Unit 6). Five of six, skipped, Unit 6 dead. Trisomy, polyploidy, Down and Klinefelter syndromes.
- Multiple alleles, ABO and Rh blood groups (Unit 2). Five of six, skipped — and the unexamined half of the unit that gave Q3 on epistasis, so you are extending a chapter you have already opened.
- Mutation, mutagenesis and DNA repair (Unit 9). Four of six, skipped, Unit 9 dead.
- Origin of life and major events in the history of life (Unit 10). Three of six, skipped, Unit 10 dead.
- Linkage, crossing over and chromosome mapping (Unit 3) and the nature and structure of genetic material (Unit 8). Both units fed nothing, and neither has a row in the repeat table at all — which does not mean they are never asked, only that our six-paper window did not catch them. Two of the largest topics in any genetics syllabus with no recorded history is a gap in our data as much as in the paper, and both are worth reading. We are checking the two unavailable papers for linkage and DNA questions.
- The current BZYCT-137 assignment. Not a topic but a method. Whatever is in this year's TMA deserves a place on your list, because that is where June 2026's four unprecedented questions came from.
What we cannot tell you. The six readable papers fall as four June sessions and only two December ones, and two whole sessions — December 2024 and December 2025 — were unavailable. That window is too skewed to say anything about December-versus-June preferences, an analysis we publish for courses where the sessions balance. Treat the ranking above as based on counts, dead units and the assignment link, not on session patterns.
If you are preparing for December 2026, our IGNOU Solved Guess Paper list builds on this pattern.
How our BZYCT-137 answers are written and checked
Every answer is written to the marks it carries. The file was written and edited by Prateek Talwar, Academic Head of Unnati Educations, and reviewed by Sheetal Kirola for accuracy and clarity.
Our writers start from the official June 2026 question wording and the BZYCT-137 blocks. Genetics answers carry worked crosses with genotype tables and ratios, because examiners look for the 12:3:1 or 9:3:4 working and not just the number. Evolution answers carry named examples — the giraffe, Weismann's mice, Mirabilis jalapa.
Before writing, the team compared the June 2026 paper with the earlier sessions on our IGNOU Previous Year Question Paper page, which is how the pattern break in section 6 came to light, and traced the four unprecedented questions back to the assignments. The two samples above are written a little longer than we advise you to write in the hall; the notes inside each say what to keep when the clock is the constraint.
BZYCT-137 solved file index for June 2026
The full file answers all 7 questions: 2 are open on this page and 5 are available only in the WhatsApp file. BZYCT-137 is a theory course, so this is a solved file index rather than a practical file index — the practical record and lab exam belong to the separate course BZYCL-138.
| Question | Topic | Marks | Course unit (our mapping) | Where to read it |
|---|---|---|---|---|
| Q1 (I) and (II) | Definitions and matching: phenotype, chromosomal aberration, diandry, vestigial organs, sympatric speciation; McClintock, Morgan, Mirabilis jalapa | 10 | Units 1, 5, 6, 7, 12, 14 [VERIFY: diandry sits in Unit 6 on numerical abnormalities rather than Unit 7 as previously mapped] | Full file only |
| Q2 | Two chromosomal sex determination mechanisms with examples | 10 | Unit 7 | Full file only |
| Q3 | Epistasis: dominant versus recessive with examples | 2 + 8 | Unit 2 | On this page |
| Q4 | Lamarckism and its assumptions | 10 | Unit 11 | On this page |
| Q5 | Chloroplast and mitochondria in extra-nuclear inheritance | 10 | Unit 4 | Full file only |
| Q6 (a) and (b) | Genetic repatterning; post-mating isolating mechanisms | 5 + 5 | Units 14 and 15 | Full file only |
| Q7 (a) and (b) | Short notes: dosage compensation; homologous organs | 5 + 5 | Units 7 and 12 | Full file only |
7 questions · counted as separately written pieces: Q1's five definitions and five matching pairs, Q3 in two parts, Q6 and Q7 in two parts each, and Q2, Q4 and Q5 as single answers · 19 written pieces in the complete file, of which 3 (both parts of Q3 and the whole of Q4) are open on this page
One item in Q1 will catch most candidates: diandry. It is the least familiar term on the paper, and in this context it means a triploid condition in which the extra chromosome set comes from the father — two paternal genomes — as against digyny, where the extra set is maternal. Learn the pair together; an answer that names its opposite shows the examiner you know the term rather than guessed it.
Programmes that include BZYCT-137 Genetics and Evolutionary Biology
BZYCT-137 is a zoology core course in IGNOU's Bachelor of Science (General), BSCG, and also appears in the Bachelor of Science Multidisciplinary, BSCM. In both programmes it is taken together with BZYCL-138, the Genetics and Evolutionary Biology laboratory course, for a combined 6 credits.
Students of the IGNOU Bachelor of Science (General) with Zoology usually meet it after the animal diversity and physiology courses. IGNOU lists the course and its lab partner on the official BSCG programme page. The semester placement differs between BSCG and BSCM, so check your own programme guide before planning your exam form.
The zoology core runs as theory-and-lab pairs, and with this course all three are in place: BZYCT-133 Comparative Anatomy and Developmental Biology with BZYCL-134, BZYCT-135 Physiology and Biochemistry with BZYCL-136, and BZYCT-137 Genetics and Evolutionary Biology with BZYCL-138 — eighteen credits in all. All three theory papers use the same 50-mark, two-hour format with a compulsory Question 1 followed by any four of six, so preparing one teaches you how to sit the other two. What differs is Question 1: BZYCT-133 mixes fill-in-the-blanks, differences and true-or-false; BZYCT-135 uses fill-in-the-blanks with matching; BZYCT-137 uses definitions with matching.
How to get the full BZYCT-137 Solved Question Paper on WhatsApp
Send a WhatsApp message to 9899436384 to get the full solved paper for June 2026 with answers to all 7 questions.
The file gives you the five answers not shown here — Q1 definitions and matching, Q2 sex determination, Q5 extra-nuclear inheritance, Q6 isolation and Q7 short notes — along with the two samples above. Write "IGNOU BZYCT 137 Solved Question Paper" in your message and our team will reply with the details.
BZYCT-137 FAQs
How do I get the full BZYCT-137 solved question paper on WhatsApp?
Send a WhatsApp message to 9899436384 and mention BZYCT 137 June 2026. The full file answers all 7 questions of the paper: the 2 samples on this page, Q3 on epistasis and Q4 on Lamarckism, plus the 5 answers not shown here, covering Q1 definitions and matching, Q2 sex determination, Q5 extra-nuclear inheritance, Q6 isolation and Q7 short notes. Our team replies with the file details.
Which BZYCT-137 June 2026 questions are solved on this page?
Two. Q3 explains epistasis and compares dominant epistasis, 12:3:1 in summer squash, with recessive epistasis, 9:3:4 in mouse coat colour, with both F2 tables worked out. Q4 explains Lamarckism and its four assumptions, with the giraffe and snake examples and Weismann's mouse experiment. The other five questions are listed as printed, and their answers are only in the full file.
Why does the BZYCT-137 June 2026 paper say BZYCT-131 in the title?
It is a printing error in the official paper. The title line reads BZYCT-131, but the header and footer of every page, and the paper's subject, Genetics and Evolutionary Biology, all match BZYCT-137. BZYCT-131 is a different zoology course. Students who sat the BZYCT-137 exam in June 2026 answered this paper, and our solved file follows it question by question.
How many questions must I attempt in the BZYCT-137 exam?
Five in total. Q1 is compulsory and carries 10 marks, made up of five definitions and a five-pair matching set. You then choose any four questions from Q2 to Q7, each worth 10 marks, for a total of 50 marks in 2 hours. Some of those questions are split — Q3 into 2 + 8, Q6 into 5 + 5, and Q7 into two notes of 5 marks each.
How long should BZYCT-137 answers be in the exam?
About 30 words a mark, which works out to roughly 280 to 320 words for a full 10-mark question, 140 to 160 for a 5-mark part or short note, 230 to 250 for the eight-mark half of Q3 and about 60 for its two-mark half. On a genetics paper a filled genotype table is worth more than the paragraph it replaces, so rule the table first and write around it. Our two samples run a little longer because they are written for revision; in the hall, write to these figures.
Which BZYCT-137 topics repeat most in IGNOU papers?
In the six official papers we hold, from June 2022 to June 2025, four topics were each asked five times: multiple alleles with ABO and Rh, numerical chromosome abnormalities, extinction, and Darwinism with natural selection. Homologous and analogous organs, structural aberrations and mutation were asked four times each. December 2024 and December 2025 were not available to us, so they are not counted.
Why did June 2026 feel so different from earlier BZYCT-137 papers?
Because it was. All four of the five-time topics above were left out, and four of its questions — sex determination, epistasis, classical Lamarckism and genetic repatterning — had never been set as full questions in any of the six earlier papers. Only five of the thirteen topics we track came back as full questions, a reuse rate of 38 per cent, the lowest we have measured on any course. A student revising only from the repeat list would have found just one familiar question among the six on offer.
Where did June 2026's new BZYCT-137 questions come from, then?
From the assignments. Sex determination, epistasis, classical Lamarckism and genetic repatterning all appear in the BZYCT-137 tutor-marked assignments of 2022 to 2024. We have seen the same thing on several other IGNOU courses, where a topic in the current assignment surfaces in the next paper, and BZYCT-137 is the strongest case we have found. The practical lesson is to read this year's assignment alongside the repeat list rather than instead of it.
Which BZYCT-137 topics should I prepare for December 2026?
Start with the four that June 2026 skipped despite a five-of-six record: Darwinism and natural selection, extinction, numerical chromosome abnormalities, and multiple alleles with ABO and Rh. Add mutation and the origin of life, both also skipped. Five of the seven units that fed nothing in June 2026 are exactly the units behind those topics, so the counts and the unit mapping agree. Then read the current assignment, and do not drop the June 2026 topics, which the paper has just proved are live.
Does BZYCT-137 have a separate practical exam?
No, it is a theory course only. The practical work sits in the companion lab course BZYCL-138, Genetics and Evolutionary Biology Laboratory, which carries 2 credits and is taken together with BZYCT-137. That is why this page gives a solved file index for the theory paper instead of a practical file index for record work.
How many credits is BZYCT-137 Genetics and Evolutionary Biology?
Four credits as a theory course, paired with the 2-credit lab BZYCL-138, so the subject adds 6 credits to your Bachelor of Science (General) or Multidisciplinary programme. The theory course is organised into 4 blocks and 16 units, moving from Mendelian genetics and chromosomes to evolution, speciation and extinction.
Who writes and checks the BZYCT-137 answers in this file?
The answers were written and edited by Prateek Talwar, Academic Head of Unnati Educations, and reviewed by Sheetal Kirola for accuracy and clarity. Each answer is sized to its marks, and genetics answers include the worked crosses and genotype tables examiners expect rather than only the final ratio.
About the authors
This page was prepared by the academic team at Unnati Educations, which has been helping IGNOU, NIOS, MDU Rohtak and GGSIPU students with solved papers and assignment support for over a decade.
Prateek Talwar, Academic Head, wrote and edited the BZYCT-137 answers and built the analysis on this page, including the question-by-question comparison against the six-paper record, the finding that all four five-time topics were skipped, and the trace of June 2026's four unprecedented questions back to the course assignments. He reads every official paper in a series before a single answer is drafted.
Sheetal Kirola reviewed this page and the solved file against the printed question wording and marks, checked both F2 tables to sixteenths, and verified the genetic and historical detail used — Bateson's 1909 use of "epistasis", the epistatic and hypostatic pair, the 12:3:1 ratio in Cucurbita pepo and the 9:3:4 ratio in mouse and Labrador coat colour, Lamarck's dates and Philosophie Zoologique (1809), the four Lamarckian assumptions and the term appetency, and Weismann's five generations and 901 mice with the somatoplasm and germplasm distinction.