CBSE Class 12 Biology Answer Key 2021 for Term-1 Exam

Biology Class 12 Answer Key Term-1

Biology Answer Key Class 12 Term-1 Paper Code- 057/2/4, Series SSJ/2: The CBSE has conducted the Class 12 board exam for the Biology paper today on 18th December 2021. The exam started at 11:30 am and was over at 1 pm. The complete CBSE Class 12 Biology Answer Key has been provided here as discussed by teachers for each question asked in today's Biology Class 12 Term-1 Exam. The students must be excited to know their probable scores to be scored in the Biology exam, and you can check to match your responses from our Biology Answer Key Class 12 Term-1 Exam.

Class 12 Biology Answer Key 2021

Class 12 CBSE Biology exam 2021 is divided into three sections A, B and C. There will be overall 60 questions and students are required to answer 50 questions as per the exam pattern released for each section. The question paper will be objective in nature. There is no provision for negative marking in the CBSE 12th board examination 2021 Term 1. The section divided are as follows:

1. Section A holds 24 questions out of which students have to attempt any 20 questions.

2. Section B holds 24 questions out of which students have to attempt any 20 questions.

3. Section C holds 12 questions out of which students have to attempt any 10 questions.

Biology Answer Key Class 12 

Earlier, official answer keys were being sent to the exam centre for evaluation purposes, as now onwards, the CBSE Board exams are conducted in the OMR sheet. Therefore no confirmation about the release of the Biology Answer Key. However, students can check their probable score using the unofficial Class 12 Biology Answer Key 2021 as prepared by our subject experts and teachers in this article.

Class 12 Biology Answer Key 2021

CBSE has set the question papers in different sets and here we have provided the Class 12 Biology Term-1 Answer Key with Question Paper PDF along with the correct answers to the questions asked in Paper Code- 057/2/4, Series SSJ/2 here in this section. 

CBSE Class 12 Biology Answer Key & Question Paper

Here, we have provided the complete Class 12 Biology Answer Key for Term-1 here with correct answers one by one. So if are looking for the complete CBSE Class 12 Biology Answer Key do check the questions & their answers below for Paper Code- 057/2/4, Series SSJ/2 

Q1. The hilum in a typical angiospermic ovule represents the junction between - 

(a) Integuments and the embryo sac. 

(b) Embryo sac and the nucellus 

(c) Body of the ovule and the funicle

(d) Nucellus and the funicle 

Answer- (c)

Q2. In the given diagram of a transverse section of a young anther. Choose the labellings showing the correct placement of the wall layers from the table given below: 

Answer- (b)

Q3. The term used for the embryo entering into the state of inactivity as the seed mature is - 

(a) Quiescent

(b) Parthenogenesis 

(c) Parthenocarpy

(d) Dormancy

Answer- (d)

Q4. The ploidy of the apomictic embryo developed from the integument cells and megaspore mother cell without reduction division respectively will be -

(a) 2n and 2n

(b) n and n 

(c) 2n and n

(d) 3n and 2n

Answer- (a)

Q5. Given below is a diagrammatic representation of a mature embryo sac of a typical angiosperm plant. Choose the option showing the correct labellings for the parts W, X, Y and Z from the table given below. 

Answer- (a)

Q6. Breast-feeding the baby acts as a natural contraceptive for the natural contraceptive for the mother because it prevents :

(i) Ovulation C 

(ii) Menstruation

(iii) Insemination 

(iv) Fertilisation Choose the correct option: 

(a) (ii) and (iv)

(b) (i) and (iii) 

(c) (i) and (iv)

(d) (i) an (ii)

Answer- (d)

Q8. During human embryonic development, the external genital organs are well developed in the foetus by the end of 

(a) 6 weeks of pregnancy

(b) 12 weeks of pregnancy 

(c) 18 weeks of pregnancy 

(d) 24 weeks of pregnancy 

Answer- (b)

Q9. The accessory ducts in the human male reproductive system consists of -

(a) Epididymis, Prostrate, Rete testis 

(b) Rete testis, Vas efferentia, Seminal vesicles 

(c) Vas efferentia, Bulbourethral, Epididymis

(d) Rete testis, epididymis, Vas deferens

Answer- (d)

Q11. An undifferentiated sheath covering the root cap of a monocotyledonous embryo is -

(a) Scutellum

(b) Coleorhiza 

(c) Coleoptile

(d) Epiblast

Answer- (d)

Q12. The cause of Down's syndrome in humans is :

(a) Extra copy of an autosome 

(b) Extra copy of a sex chromosome 

(c) Absence of an autosome 

(d) Absence of a sex chromosome 

Answer- (a)

Q13 Which of the following features show the mechanism of sex determination in honey-bee? 

(i) An offspring formed from the union of a sperm and egg develops as a male. 

(ii) Males have half the number of chromosomes than that of female. 

(iii) The females are diploid having 32 chromosomes. 

(iv) Males have father and can produce sons. 

(a) (i) and (ii)

(b) (ii) and (iii) 

(c) (i) and (iv)

(d) (ii) and (iv)

Answer- (b)

Q14.  Select the pair that is incorrect :

(a) Sickle-cell anemia : Autosome linked recessive trait

(b) Haemophilia : Autosome linked recessive trait

(c), Colour blindness : Sex linked recessive trait 

(d) Thalassemia : Autosome linked recessive traita

Answer- (b)

Q15. An example of a human trait where a single gene can exhibit multiple phenotypic expressions is -

(a) Phenyl ketonuria

(b) Cystic fibrosis 

(c) Thalassemia

(d) Haemophilia

Answer- (a)

Q16. Life cycle of Drosophila melanogaster is completed in -

(a) 7 days

b) 14 days 

(c) 21 days

(d) 28 days

Answer- (b)

Q17. How many types of gametes would develop by an organism with genotype?

(a) 1

(b) 2

(c) 3

(d) 4

Answer- (d)

Q18. Given below are the observations drawn in HGP. Select the option that shows the correct observations. 

(i) The human genome contains 3164.7 billion base pairs.com 

(ii) The average gene consists of 3000 bases.com 

(iii) Less than 2% of the genome codes for proteins. 

(iv) Chromosome one has most genes (2698) . 

(a) (i) and (ii)

(b) (ii) and (iii) 

(c) (iii) and (iv)

(d) (i) and (iii)

Answer- (b)

Q19. The phosphoester linkage in the formation of a nucleotide involves the bonding between 

(a) Phosphate group and OH of 3'C of a nucleoside 

(b) Phosphate group and OH of 5'C of a nucleoside 

(c) Phosphate group and H of 3'C of a nucleoside 

(d) Phosphate group and H of 5'C of a nucleoside

Answer- (a)

Q20. The switching 'on' and 'off of the lac operon in prokaryotes is regulated by

(a) Glucose

(b) Galactose 

(c) Lactose

(d) Fructose

Answer- (c)

Q21. 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? 

(a) Ribonucleotide triphosphate 

(b) Deoxyribonucleoside triphosphate 

(c) Deoxyribonucleotide triphosphate 

(d) Ribonucleoside triphosphate

Answer- (c)

Q22. Which one of the following factor will associate transiently with RNA polymerase to terminate transcription in prokaryotes?

(a) sigma factors

(b) RHO factor 

(c) delta factor

(d) theta factor 

Answer- (b)

Q23.  Choose the correct pair of codon with its corresponding amino acid from the following list : 

(a) UAG: Glycine

(b) AUG : Arginine 

(c) UUU: Phenylalanine 

(d) UGA: Methionine 

Answer- (Answer- (b))

Q24. During the elongation process of translation, the peptide bond formation between amino acids is catalysed by - 

(a) ribosomal RNA 

(b) protein in the small subunit of the ribosome 

(c) protein in the large subunit of the ribosome

(d) transfer RNA

Answer- (a)

Question No. 25 to 28 consists 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, but (R) is not the correct explanation of (A). 

(c) (A) is true but (R) is false. 

(d) (A) is false but (R) is true. 

Q25. 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 with other reasons for this.

Answer- (a) 

Q26. Assertion (A): Sterilisation methods are generally advised for a male partner as a terminal method to prevent any more pregnancies.

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

Answer- (c) 

Q27. Assertion (A): The inner cell mass of the 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.

Answer- (a) 

Q28. Assertion (A): There is an expression of only one gene of the parental character in a Mendelian Monohybrid cross in Fi generation. 

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

Answer- (b) 

Q29. Select the correct option for Human Chorionic Gonadotropin (HCG) released during embryonic development in humans. 

(i) Helps in the maintenance of pregnancy. 

(ii) Leads to rupture of Graafian follicle. 

(iii) Cause strong uterine contraction during childbirth. 

(iv) Brings metabolic changes in the mother. 

(a) (i) and (ii)

(b) (i) and (iv) 

(c) (ii) and (iii)

(d) (ii) and (iv)

Answer- (b) 

Q30. Residual persistent nucellus in black pepper is known as

(a) Perisperm

(b) Pericarp 

(c) Pulvinus

(d) Perianth

Answer- (a) 

Biology Class 12 Term-1 Question Paper- 057/2/4

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