Mizoram Mbse Class 12 Biology — Real Previous-Year Papers

Haemophilia is a disease that usually appears in male but rarely in female. However, female can become haemophilic if - (i) Mother is haemophillic and father is normal (ii) Mother is a carrier and father is normal (iii) Mother is normal and father is haemophillic (iv) Mother is a carrier and father is haemophillic

Trichophyton, a fungus causes which of the following diseases - (i) Ringworm (ii) Cholera (iii) Mumps (iv) Psoriasis

Which of the following is wrongly matched ? (i) Butyric acid - rincidity of butter (ii) Lipases - fat digesting enzyme (iii) Cyclosporin A - immunosuppressive agent (iv) Streptokinase - blood cholesterol lowering agent

A family residing in a rural area needs a clean and cheap fuel that produces very few pollutants. Which microbes will you suggest for this family ? (i) Aerobic bacteria called Methanobacterium (ii) Anaerobic bacteria called Methanobacterium (iii) Aerobic bacteria called Mycobacterium (iv) Anaerobic bacteria called Mycobacterium

A cytokine barrier, which is an innate immunity, depends on the production of certain substance by an infected cells that protects other cells from further infection. Identify this substance - (i) Histamine (ii) Serotonin (iii) Interferon (iv) Phagocyte

Which one of the following is not required for rDNA technology ? (i) DNA polymerase (ii) DNA ligase (iii) Restriction endonuclease (iv) Reverse transcriptase

Insulin is a hormone produced by beta cell of pancreas. It controls the blood sugar level in the blood by - (i) Converting glycogen into glucose (ii) Converting glucose into glycogen (iii) Converting glucose into galactose (iv) Excretion of sugar by kidneys

Transgenic animals carry a gene/genes from another species in their genome. One can identify such animals by observing - (i) foreign RNA in all its cells (ii) foreign DNA in some of its cells (iii) foreign DNA in all its cells (iv) Both (i) and (ii)

A boy is born with a hereditary disease, what corrective method will you suggest ? (i) Gene cloning (ii) Nuclear transfer (iii) Organism cloning (iv) Gene therapy

Individuals affected by STDs like AIDS face discrimination in the society since sexually transmitted diseases have social stigma attached to it. As a result of this, they face a lot of health issues. Mention any four health issues/complications faced by them.

According to scientists, the great diversity that exists today is a result of 3500 million years of evolution. But according to Hardy-Weinberg's principle, evolution will not occur if certain conditions are met. Elucidate any two conditions that will not permit evolution. **OR** A 9 years old boy Ruatpuia was kidnapped from his backyard. His parents reported him missing and an investigation was launched. After the investigation, police found saliva on a discarded water bottle near the crime scene. (i) What technique will the police use to identify the kidnappers ? (ii) Explain the basic principle of this technique.

Predict the possible blood group of the offspring when father is heterozygous A and mother have blood group O.

Explain how Rhizobium acts as a biofertilizer. **OR** What are antibiotics ? Write the name of two commonly used antibiotics obtained from bacteria.

Write any two differences between B cells and T cells.

How can Bt cotton help the farmers ?

Argue for or against the statement and give at least two points to support your answer - "Gene cloning violates the right and dignity of a species and should be banned completely".

What is 10 % law ? Why are trophic levels limited to 4-5 at the maximum ?

After the process of decomposition of detritus, it undergoes two very important processes. Elucidate these processes. **OR** Oceans occupy 70 % of the surface of our planet but their NPP is far less than land ecosystem. What could be the reasons for low productivity of oceans ? Give two reasons.

Write two differences between National parks and Wildlife sanctuaries.

From the above diagram - Identify X and Y

From the above diagram - Name the microbe from which a heat stable (thermostable) enzyme is isolated.

From the above diagram - What is the role of Y ?

From the above diagram - What will happen to this biological process if X did not take place ?

Explain the development of placenta and write how it regulates the exchange of substances between maternal and foetal blood.

Mongolism is an autosomal disorder in which the affected individuals have similar facial features. Explain the primary cause of this disorder. Write any four visible symptoms of this disease.

Explain Darwin's theory of evolution by natural selection.

A 15 years old girl named Ruati experiences severe allergic reactions to crabs. How would you explain the immunological mechanisms involved in Ruati's allergic response to crabs. Support your answer with a suitable diagram. **OR** Describe the treatment of sewage by aerobic microbes.

Mizoram is blessed with rich biodiversity as it is a part of Indo-Myanmar biodiversity hotspot. Mention two important features that make our state qualified to be considered as a megadiversity zone. Do you think there is an urgent need to conserve our biodversity ? If yes, validate your reasons.

Describe the development of a mature embryosac from a functional megaspore with a suitable diagram.

How are introns removed in eukaryotic gene ? Describe the structure of an eukaryotic gene with diagrams. **OR** A single strand of RNA is formed from a single DNA strand. What is this process called ? Explain the sequence of events during this process with suitable diagrams. Also give reasons why both the strand of DNA are not copied during this process.