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CBSE Class 12 Biology Previous Year Question Paper Term 1 2021 SSJ-2-Set-4

From learning about radioactive wastes and genetics to understanding food production and reproductive health, your Class 12 Science syllabus for Biology introduces you to a wealth of information. On TopperLearning, we have collated the most preferred learning resources for you to study and revise all the chapters in Biology with ease.

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Section – A consists of 24 questions. Attempt any 20 questions from this section. 

The first attempted 20 questions would be evaluated.


Question 1. 

The hilum in a typical angiospermic ovule represents the junction between -

  1. Integuments and the embryo sac
  2. Embryo sac and the nucellus
  3. Body of the ovule and the funicle
  4. Nucellus and the funicle


Question 2.        

In the given diagram of a transverse section of a young anther. Choose the labellings showing correct placement of the wall layers from the table given below:


Question 3.

The term used for the embryo entering into the state of inactivity as the seed mature is -

  1. Quiescent
  2. Parthenogenesis
  3. Parthenocarpy
  4. Dormancy


Question 4.

The ploidy of the apomictic embryo developed from the integument cells and megaspore mother cell without reduction division respectively will be - 

  1. 2n and 2n
  2. n and n
  3. 2n and n
  4. 3n and 2n


Question 5.

Given below is a diagrammatic representation of a mature embryo sac of a typical angiosperm plant.

Choose the option showing the correct labelling for the parts W, X, Y and Z from the table given below.

Question 6. 
Breast – feeding the baby acts as a natural contraceptive for the mother because it prevents:
  1. Ovulation 
  2. Menstruation
  3. Insemination
  4. Fertilization
Choose the correct option:
  1. (ii) and (iv)
  2. (i) and (iii)
  3. (i) and (iv)
  4. (i) and (ii)
Question 7.
The given figure shows the different stages of human embryo.
Identify the correct labellings for W, X, Y and Z and choose the correct option from the table below:
Question 8. 
During human embryonic development the external genital organs are well developed in the fetus by the end of -
  1. 6 weeks of pregnancy
  2. 12 weeks of pregnancy
  3. 18 weeks of pregnancy 
  4. 24 weeks of pregnancy
Question 9.   
The accessory ducts in the human male reproductive system consists of -
  1. Epididymis, Prostrate, Rete testis
  2. Rete testis, Vas efferentia, Seminal vesicles
  3. Vas efferentia, Bulbourethral, Epididymis
  4. Rete testis, epididymis, Vas deferens
Question 10.
Given below is a figure of an angiosperm plant showing two different types flowers ‘X’ and ‘Y’ and the possible type of pollination in them:
Select the correct option for the flower (X) and flower (Y) and the possible type of pollination from the given table:
Question 11. 
An undifferentiated sheath covering the root cap of a monocotyledonous embryo is
  1. Scutellum 
  2. Coleorhiza
  3. Coleoptile
  4. Epiblast
Question 12. 
The Cause of Down’s syndrome in humans is:
  1. Extra copy of an autosome
  2. Extra copy of a sex chromosome
  3. Absence of an autosome
  4. Absence of a sex chromosome
Question 13. 
What of the following features show the mechanism of sex determination in honey – bee?
  1. An offspring formed from the union of a sperm and egg develops as a male.
  2. Males have half the number of chromosomes than that of female.
  3. The females are diploid having 32 chromosomes.
  4. Males have father and can produce sons.
  1. (i) and (ii)
  2. (ii) and (iii)
  3. (i) and (iv)
  4. (ii) and (iv)
Question 14.
Select the pair that is incorrect:
  1. Sickle-cell anemia : Autosome linked recessive trait
  2. Haemophilia : Autosome linked recessive trait
  3. Colour blindness : Sex linked recessive trait
  4. Thalassemia : Autosome linked recessive trait
Question 15. 
An example of a human trait where a single gene can exhibit multiple phenotypic expression is - 
  1. Phenyl ketonuria
  2. Cystic fibrosis
  3. Thalassemia 
  4. Haemophilia


Question 16. 

Life cycle of Drosophila melanogaster is completed in -

  1. 7 days 
  2. 14 days
  3. 21 days 
  4. 28 days


Question 17.   

How many types of gametes would develop by an organism with genotypes AaBBCcDD?

  1. 1
  2. 2
  3. 3
  4. 4


Question 18. 

Given below are the observations drawn in HGP. Select the option that shows the correct observations.

  1. The human genome contains 3164.7 billion base pairs.
  2. The average gene consists of 3000 bases.
  3. Less than 2% of the genome codes for proteins.
  4. Chromosome one has most genes (2698).
  1. (i) and (ii)
  2. (ii) and (iii)
  3. (iii) and (iv)
  4. (i) and (iii)


Question 19.   

The phosphoester linkage in the formation of a nucleotide involves the bonding between 

  1. Phosphate group and OH of 3’C of a nucleoside
  2. Phosphate group and OH of 5’C of a nucleoside
  3. Phosphate group and H of 3’C of a nucleoside 
  4. Phosphate group and H of 5’C of a nucleoside


Question 20.     

The switching ‘on’ and ‘off’ of the lac operon in prokaryotes is regulated by 

  1. Glucose
  2. Galactose
  3. Lactose
  4. Fructose
Question 21.
For 'in-vitro' DNA replication, which one of the following substrates need to be added along with the necessary enzymes, the DNA template and specific conditions? 
  1. Ribonucleotide triphosphate 
  2. Deoxyribonucleoside triphosphate
  3. Deoxyribonucleotide triphosphate
  4. Ribonucleoside triphosphate 
Question 22.
Which one of the following factor will associate transiently with RNA polymerase to terminate transcription in prokaryotes? 
  1. sigma factor 
  2. RHO factor
  3. Delta Factor
  4. Theta factor
Question 23.
Choose the correct pair of codon with its corresponding amino acid from the following list:
  1. UAG: Glycine 
  2. AUG: Arginine
  3. UUU: Phenylalanine 
  4. UGA : Methionine
Question 24.
During elongation process of translation, the peptide bond formation between amino acids is catalysed by - 
  1. ribosomal RNA
  2. Protein in small subunit of ribosome 
  3. Protein in large subunit of ribosome 
  4. transfer RNA



Section - B consists of 24 questions (Sl. No.25 to 48). Attempt any 20 questions from this section.

The first attempted 20 questions would be evaluated.

Question No. 25 to 28 consist of two statements –


Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below: 

A. Both A and R are true and R is the correct explanation of A 

B. Both A and R are true and R is not the correct explanation of A 

C. A is true but R is false 

D. A is False but R is true


Question 25.

Assertion (A): Through Reproductive and Child Health (RCH) programmes in India, we could bring down the population growth rate. 

Reason (R): A rapid increase in MMR and IMR were the reasons, along other reasons for this.


Question 26.

Assertion (A): Sterilisation methods are generally advised for male/ female partner as a terminal method to prevent any more pregnancies.

Reason (R): These techniques are less effective and have high reversibility. 


Question 27.

Assertion (A): The inner cell mass of blastocyst gets attached to the endometrium during embryonic development in humans. 

Reason (R): The blastomeres in the blastocyst gets arranged into trophoblast and inner cell mass.


Question 28.

Assertion (A): There is expression of only one gene of the parental character in a Mendelian Monohybrid cross in F1 generation. 

Reason (R): In a dissimilar pair of factor one member of the pair dominates the other.


Question 29.

Select the correct option for Human Chorionic Gonadotropin (HCG) released during embryonic development in humans.

  1. Helps in maintains of pregnancy.
  2. Leads to rupture of Graafian follicle. 
  3. Cause strong uterine contraction during childbirth.
  4. Brings metabolic changes in the mother. 
  1. (i) and (ii)
  2. (i) and (iv)
  3. (ii)  and (iii) 
  4. (ii) and (iv)


Question 30.

Residual persistent nucellus in black pepper is known as 

  1. Perisperm
  2. Pericarp 
  3. Pulvinus 
  4. Perianth 


Question 31.

Amongst the insects the dominant biotic pollinating agents are –

  1. Ants
  2. Wasps
  3. Beetles 
  4. Bees


Question 32.

The source of gonadotropin LH and its corresponding function is

  1. Anterior pituitary, ovulation
  2. Anterior pituitary Graafian follicle formation
  3. Hypothalamus Ovulation 
  4. Hypothalamus, Graafian follicle formation


Question 33.

A specialized procedure to form an embryo in the laboratory in which sperm is directly, injected into the ovum is 

  1. IUT 
  2. IUI
  3. ICSI
  4. ZIFT


Question 34.

Listed below are all reproductive tract infections except 

  1. Genital herpes 
  2. Filariasis
  3. Trichomoniasis
  4. Syphilis 


Question 35.

A genetic mechanism which prevents inbreeding depression in majority of angiospermic plants is 

  1. Parthenogenesis
  2. Parthenocarpy
  3. Mutation
  4. Self-incompatibility


Question 36.

In Pisum sativum the flower colour may be Violet (V) or White (v). What proportion of the offsprings in a cross of VV × vv would be expected to be violet?

  1. 25%
  2. 50%
  3. 75% 
  4. 100%


Question 37. 

Which one of the gene pair is expected to give a ratio of 1:1:1:1 in the progeny of a Mendelian Dihybrid cross?

  1. AaBb × AaBb
  2. AABB × AaBb
  3. AaBb  ×aabb
  4. AABB × aabb
Question 38.
The progeny of a cross between two snap dragon plants, heterozygous for flower colour, bearing different coloured flower would be:
  1. 50% pink,50% white
  2. 25% red, 50% pink, 25% white
  3. 50% red, 50% white
  4. 75% red, 25% white
Question 39. 
Study the given pedigree of a family and select the trait that shows this pattern of inheritance:
  1. Autosomal recessive, Phenylketonuria
  2. Sex –linked recessive, colour- blindness
  3. Autosomal dominant, Myotonic dystrophy
  4. Sex – linked dominant, Vitamin – D resistant Rickets
Question 40.
A child with blood Group A has father with blood group B and mother with blood group AB. What would be the possible genotypes of parents and the child? Choose the correct option:
Father     Mother    Child
  1. IAi            IBi           IAi
  2. IAIB          IAi           IAIA
  3. IBi            IAIB         IAi
  4. IBIB          IAIB         IAIA
Question 41. 
In a dihybrid Mendelian cross, garden pea plants heterozygous for violet flowers and round seeds are crossed with homozygous, white and wrinkled seeds. The genotypic and phenotypic ratio of F1 progeny would be.
  1. 9 : 3 : 3 : 1
  2. 1 : 2 : 2 : 1 
  3. 1 : 1 : 1 : 1 
  4. 3 : 1 
Question 42.
A region of coding strand of DNA has the following nucleotide sequence: 
5’ - TGCGCCA -3'
The sequence of bases on mRNA transcribed by this DNA strand would be:
  1. 3' — ACGC0GT — 5'
  2. 5’ — ACGCGGT — 3’
  3. 5’ — UGCGCCA — 3' 
  4. 3’ — UGCGCCA —5'
Question 43.
A DNA molecule is 160 base pairs long. It has 20% adenine. How many cytosine bases are present in this DNA molecule?
  1. 192 
  2. 96 
  3. 64
  4. 42
Question 44.
A template strand in a bacterial DNA has the following base sequence:
5' — TTTAACGAGG - 3' 
What would be the RNA sequence transcribed from this template DNA?
  1. 5'— AAATTGCTCC — 3'
  2. 3’— AAATTGCTCC — 5'
  3. 3 '— AAAUUCCUCC — 3’
  4. 5'— CCUCGUUAAA — 3'
Question 45.
Colour-blindness is a sex linked recessive trait in humans. A man with normal colour vision marries a women who is colourblind. What would be the possible genotypes of the parents, the son and the daughter of this couple?
Mother    Father    Daughter    Son
  1. XX          XeY         XCX          XY
  2. XCXC      XeY         XCXC        XCY
  3. XCX         XY          XCX          XY
  4. XCXC       XY          XCX         XCY


Question 46.

tRNA has an __________ that has bases complementary to the codon, its actual structure is a compact molecule which looks like ___________. Select the option that has correct choices for the two blanks.

  1. amino acid acceptor end, clover-leaf
  2. anticodon loop, clover-leaf
  3. amino acid acceptor end, inverted L
  4. anticodon loop, inverted L


Question 47.

Which type of RNA is correctly paired with its function?

  1. small nuclear RNA: Possesses rRNA
  2. transfer RNA : attaches to amino acid
  3. ribosomal RNA : involved in transcription
  4. micro RNA : involved in translation


Question 48.

Given below are the pairs of contrasting traits in Pisum sativum as studied by Mendel. Select the incorrectly mentioned option from the table given below:


Section –C consists of one rage followed by 6 questions linked to this case (Q. No. 49 to 54). Besides this, 6 more questions are given. Attempt any 10 questions in this section. 

The first attempted 10 questions would be evaluated.



A women of 35 years age with a married life of eight years and having normal reproductive cycles visits a doctor along with her husband for consultation for infertility. They were not using any contraceptive methods. They have no child. The doctor advises them alter a detailed physical examination of both of them to undergo following investigations:

- Seminal analysis of the husband 

- Follicular study of the wife

- Blood test for Follicle Stimulating Hormone (FSH) estimation for both. 

With your basic knowledge of human embryology and the case given above, answer the following questions (49-54)

Question 49.
Seminal analysis of the husband was done for determining
  1. Sperm morphology and sperm count  
  2. Quantity and pH of semen 
  3. Rate of sperm release into the Vagina 
  1. (i) only
  2. (i) and(ii)
  3. (ii) and (iii)
  4. (ii) only
Question 50.
An ultrasound - guided follicular study was done for the wife for determining the size and physical appearance of the
  1. Ovary 
  2. Oogonia
  3. Antral follicles  
  4. Corpus Luteum
Question 51.
The blood test report of the wife showed low FSH value, which is indicative of -
  1. low rate of formation of ovarian follicles 
  2. high rate of formation of ovarian follicles
  3. low rate of maturation of ovarian follicles 
  4. high rate of maturation of ovarian follicles 
Question 52.
In the above case if the husband is found to have sperm count of less than 20 million/mL and the wife is diagnosed with blockage in the oviduct, the couple would be advised for:
  1. ZIFT
  2. Al 
  3. IVF
  4. ICST
  1. (i) and (iii) 
  2. (ii) and (iii)
  3. (iii) and (iv) 
  4. (i) and (iv)
Question 53.
The high level of which gonadotropin/ovarian hormone in the blood sample of the wife taken on day 20 of her reproductive (menstrual) cycle would indicate the luteal phase of the ovarian cycle ? 
  1. FSH
  2. LH 
  3. Estrogens 
  4. Progesterone
Question 54.
In which phase of the menstrual cycle is the blood sample of a women taken if, on analysts. It shows high levels of L.H. and estrogen?
  1. Ovulatory phase
  2. Menstrual phase
  3. Secretory phase
  4. Follicular phase 
Question 55.
How many types of gametes can be produced in a diploid organism which is heterozygous for 4 loci?
  1. 8
  2. 16
  3. 32
Question 56.
Given below a Karyotype obtained after analysis of fetal cells for probable genetic disorder.
Based on the above karyotype, the chromosomal disorder detected in unborn foetus and the consequent symptoms the child may suffer from are-
  1. Down's syndrome : Gynaecomastia, overall masculine development 
  2. Down's syndrome : Furrowed tongue, short stature
  3. Klinefelter's syndrome : Gynaecomastia, Masculine development
  4. Klinefelter's syndrome : Rudimentary ovaries, short stature
Question 57.
 The recombinant frequency between the four linked genes is as follows:
  1. between X and Y is 40%. 
  2. between Y and Z is 30% 
  3. between Z and W is 10%
  4. between W and X is 20%
Select the option that shows the correct order of the position of W, X, Y and Z genes on the chromosome:
  1. Y - X – Z - W 
  2. Y – W – Z - X 
  3. X – Y - Z - W
  4. Z – X – Y - W
Question 58.
The figure given below has labellings (i), (ii) and (iii), which two labellings in the given figure are components of a nucleosome? Select the correct option.
  1. (i) - HI histone, (ii) - DNA
  2. (i) - DNA, (ii) - Historic Octamer
  3. (ii) - DNA, (iii) - HI Histone
  4. (ii) - Histone octamer, (iii) - DNA
Question 59.
Which one of the following diagram is a correct depiction of a polynucleotide chain to DNA?
Question 60.
In molecular biology who proposed that genetic information flows in one direction?
  1. Hargobind Khorana
  2. Francis Crick
  3. Watson and Crick
  4. Marshall Nirenberg