West Bengal Wbchse Class 12 Biology — Real Previous-Year Papers

In the following question, a statement of Assertion (A) is followed by a statement of Reason (R). Read the statements and choose the correct option : Assertion (A) : Some fruits are seedless, and the demand for these fruits is increasing. Reason (R) : These fruits are produced without fertilization. (a) Both (A) and (R) are true and (R) is the correct explanation of (A) (b) Both (A) and (R) are true but (R) is not the correct explanation of (A) (c) (A) is true, but (R) is false (d) Both (A) and (R) are false

A couple was interested to know the gender of their embryo. The doctor, refused to do so as it is illegal. But, if the doctor intended to disclose which of the following methods will he follow ? (a) IVF (b) Amniocentesis (c) ART (d) IUD

____ is not a veneral disease. (a) Hepatitis-B (b) Malaria (c) Trichomoniasis (d) Syphilis

In the following question, a statement of Assertion (A) is followed by a statement of Reason (R). Read the statements and choose the correct option : Assertion (A) : Reproductive health is related to physical health. Reason (R) : Reproductive health also refers to behavioural health. (a) Both (A) and (R) are true and (R) is the correct explanation of (A) (b) Both (A) and (R) are true but (R) is not the correct explanation of (A) (c) (A) is true, but (R) is false (d) Both (A) and (R) are false

State the names of the hormones I, II, III, IV according to the following diagram : (a) (I) — Inhibin, (II) — Testosterone, (III) — FSH, (IV) — GnRH (b) (I) — Testosterone, (II) — Inhibin, (III) — FSH, (IV) — GnRH (c) (I) — GnRH, (II) — Testosterone, (III) — Inhibin, (IV) — FSH (d) (I) — GnRH, (II) — FSH, (III) — Testosterone, (IV) — Inhibin

Identify the correct sequence of phases during menstrual cycle : (a) Bleeding phase → Ovulatory phase → Follicular phase → Luteal phase (b) Ovulatory phase → Bleeding phase → Follicular phase → Luteal phase (c) Bleeding phase → Follicular phase → Ovulatory phase → Luteal phase (d) Luteal phase → Follicular phase → Ovulatory phase → Bleeding phase

Verify the following sentences True or False and select the correct option : — Lactation is the process of milk secretion from the mammary glands. — Lactation occurs with the help of oxytocin hormone. (a) Both sentences are true (b) The first sentence is true, but the second sentence is false (c) The first sentence is false, but the second sentence is true (d) Both sentences are false

Select the correct option given below to fill in the blanks : Produced in the ovary after ovulation, ____ acts as a temporary endocrine gland to secrete ____ hormone. (a) Graafian follicle, Progesterone (b) Primordial follicle, Oestrogen (c) Tunica albuginea, Oestrogen (d) Corpus luteum, Progesterone

The layer from which gametes are formed is (a) Columnar epithelium tissue (b) Granular epithelium tissue (c) Germinal epithelium tissue (d) Follicular epithelium tissue

Match the Column-I with Column-II : Column-I : i) Sertoli cells ii) Zona pellucida iii) Placenta iv) Uterine endometrium ; Column-II : a) Layer of the ovum b) Spermiogenesis c) Implantation d) Human chorionic Gonadotropin. Choose the correct answer from the options below : (a) i-a, ii-c, iii-b, iv-d (b) i-c, ii-d, iii-a, iv-b (c) i-b, ii-a, iii-d, iv-c (d) i-d, ii-b, iii-c, iv-a

Types of gametes which may be produced by an organism having genotype XxYyZz are (a) 4 (b) 8 (c) 6 (d) 2

The ratio of organisms produced in the cross AaBb × aabb will be (a) 3 : 3 : 1 : 1 (b) 1 : 1 : 1 : 1 (c) 9 : 3 : 3 : 1 (d) 3 : 1 : 3 : 1

Match Column-I with Column-II and select the correct option : Column-I : i) Telocentric chromosome ii) Acrocentric chromosome iii) Submetacentric chromosome iv) Metacentric chromosome ; Column-II : a) V shaped b) I shaped c) J shaped d) L shaped. (a) i-a, ii-b, iii-c, iv-d (b) i-b, ii-a, iii-d, iv-c (c) i-d, ii-c, iii-b, iv-a (d) i-d, ii-a, iii-b, iv-c

In the following question, a statement of Assertion (A) is followed by a statement of Reason (R). Read the two statements and select the correct answer : Assertion (A) : Female birds are heterogametic and male birds are homogametic. Reason (R) : The sex chromosomes of female birds are ZW and the sex chromosomes of male birds are ZZ. (a) Both (A) and (R) are true and (R) is the correct explanation of (A) (b) Both (A) and (R) are true but (R) is not the correct explanation of (A) (c) (A) is true, but (R) is false (d) Both (A) and (R) are false

In Mirabilis sp. the appearance of pink hybrid (Rr) between cross of a red (RR) and white (rr) flower plant parent, indicates (a) Incomplete dominance (b) Segregation (c) Co-dominance (d) Independent assortment

Which of the following factors does not affect Hardy-Weinberg Principle ? (a) Gene flow (b) Mutation (c) Migration (d) Recapitulation

Which of the following is not an example of Polygenic inheritance ? (a) Human skin colour (b) ABO blood group (c) Grain colour of wheat (d) Human body height

Read the following passage below and answer next four questions (23 - 26) related to it : In his experiment Griffith isolated two strains of bacteria, one was rough walled with pili on the wall and the other one covered with an extremely slimy coat hence smooth in nature. He injected type II R to mice and the mice could survive. Type III S was injected to mice and it died of Pneumonia. Heat killed (HK) strains of the same (Type III S) when injected to the mice, it was alive or did not die. But when the mice was injected with III S (HK) and II R mixed the mice was found to be dead and virulent III S were recovered from the dead remains of the mice. [Q23] Name the process which is observed in this experiment : (a) Bacterial transduction (b) Bacterial transformation (c) Bacterial conjugation (d) Bacterial transfection

Which bacteria was used in this famous experiment by Griffith ? (a) Diplococcus pneumoniae (b) Bacillus subtilis (c) Haemophilus influenzae (d) E. coli

Which of the following statements is incorrect about HK III (S) ? (a) Heat killed III S strain was rough in nature (b) Avirulent (c) Heat killed III S strain was smooth in nature (d) Type III S bacterial strain was heated at high temperature to make the heat killed strain HK III S

Why do HK III S + II R when administered together, they become deadly ? (a) III S remain unchanged (b) II R remain avirulent (c) The avirulent II R changed to type III S (d) The HK III S changed to type II R and got virulent

Which of the following statements is correct regarding the process of replication in E. coli ? (a) The DNA dependent DNA polymerase catalyses polymerization in 5′ → 3′ direction (b) The DNA dependent DNA polymerase catalyses polymerization in one direction that is 3′ → 5′ (c) The DNA dependent RNA polymerase catalyses polymerization in one direction that is 5′ → 3′ (d) The DNA dependent DNA polymerase catalyses polymerization in 5′ → 3′ as well as 3′ → 5′ direction

Protein that helps to stabilise the replication fork and protect the separated single strand of DNA from reannealing, during DNA replication is (a) Helicase (b) Ligase (c) SSB (d) Primase

Verify the following sentences True/False and select the correct option : — Genetic RNA is present in RNA viruses. — mRNA is non-genetic RNA. (a) Both sentences are true (b) The first sentence is true, but the second sentence is false (c) The first sentence is false, but the second sentence is true (d) Both sentences are false

In E. coli, the Lac operon gets switched on when (a) Lactose is present and it binds to the repressor (b) Repressor binds to operator (c) RNA polymerase binds to the operator (d) Lactose is present and it binds to RNA polymerase

Deoxyribonucleoside triphosphate serves dual purposes. The purposes are I. Acting as substrate II. Acting as enzyme III. Provides energy for polymerisation IV. Decreases the rate of the reaction. Choose the correct option : (a) I and II (b) II and III (c) III and IV (d) I and III

The net electric charges on DNA and histones are (a) Both positive (b) Both negative (c) Negative and positive respectively (d) Zero

Palaeontological evidences for evolution refer to the (a) Development of embryo (b) Homologous organs (c) Fossils (d) Analogous organs

Match Column-I with Column-II and select the correct option : Column-I : i) Phylloclade of Opuntia, stem tendril of Passiflora ii) Archaeopteryx iii) Sphenodon, Limulus iv) Bat wings, insect wings v) Ornithorhynchus ; Column-II : a) Connecting link between reptiles and mammals b) Living fossils c) Analogous organs d) Missing link between reptiles and birds e) Homologous organs. (a) i-e, ii-c, iii-d, iv-b, v-a (b) i-b, ii-c, iii-a, iv-e, v-d (c) i-e, ii-b, iii-d, iv-c, v-a (d) i-b, ii-e, iii-a, iv-c, v-d

Which of the following isotopes is used for finding the fossil age maximum about 3,50,000 years ? (a) ²³⁸U (b) ¹⁴C (c) ³H (d) ²⁰⁶Pb