CBSE Class 12 Biology Answer Key 2021-2022 – Central Board of Secondary Education (CBSE) has conducted the class 12 Biology Term 1 exam on December 18, 2021. The answer key for the same is released by various subject teachers and coaching institutes online at their respective youtube channel and websites. Students can check CBSE Class 12 Biology answer key here as well.
Paper Code: 057/2/4
| 1(c) | 2(b) | c(d) | 4 (a) | 5 (a) | 6(d) |
| 7(c) | 8(d) | 9(d) | 10(c) | 11(b) | 12(a) |
| 13(b) | 14(b) | 15(a) | 16(b) | 17(d) | 18(b) |
| 19(a) | 20(c) | 21(c) | 22(b) | 23(c) | 24(a) |
| 25(a) | 26(c) | 27(a) | 28(b) | 29(b) | 30(a) |
| 31(d) | 32(a) | 33(c) | 34(d) | 35(d) | 36(d) |
| 37(c) | 38(b) | 39(a) | 40(c) | 41(c) | 42(c) |
| 43(b) | 44() | 45(d) | 46(b) | 47(b) | 48(a) |
| 49(b) | 50(c) | 51(a) | 52(b) | 53(d) | 54(a) |
| 55(c) | 56(c) | 57(d) | 58(d) | 59(b) | 60(b) |
Paper Code: 057/3/4
| 1(a) | 2(a) | 3(c) | 4(c) | 5(b) | 6(d) | 7(b) | 8(c) | 9(c) | 10(c) |
| 11(c) | 12(b) | 13(c) | 14(b) | 15(c) | 16(b) | 17(d) | 18(c) | 19(d) | 20(c) |
| 21(c) | 22(b) | 23(a) | 24(c) | 25(b) | 26(a) | 27(d) | 28(b) | 29(d) | 30(c) |
| 31(d) | 32(c) | 33(d) | 34(b) | 35(c) | 36(b) | 37(c) | 38(d) | 39(b) | 40(b) |
| 41(c) | 42(a) | 43(b) | 44() | 45(b) | 46(a) | 47(c) | 48(d) | 49(a) | 50(a) |
| 51(c) | 52(a) | 53(a) | 54(b) | 55(b) | 56(b) | 57(a) | 58(c) | 59(d) | 60(b) |
Ques. The hilum is a typical angiosperm ovule respresents the junction between –
Ans. Body of the ovule and funicle
Ques. In the given diagram of a transverse section of a younger anther. Choose the labelling showing the correct placement of the wall layers from the table given below.
Ans. Tapetum, Endothecium, Epidermis, Middle layers
Ques. The term used for the embryo entering into the state of inactivity as the seed mature is –
Ans. Doremancy
Ques. The ploidy of the apomictic embryo development from the integument cells and megaspore mother cell without reduction division respectively will be-
Ans. 2n and 2n
Ques. Given below is a diagrammatic representation of a mature embryo sac of a typical angiosperm plant.
Ans. Micropylar end, Antipodals, Synergids, Central Cell
Ques. Breast-freeding the baby act as a natural contraceptive for the mother because it prevents-
i) Ovulation
ii) Menstruation
iii) Insemination
iv) Fertilisation
Choose the correct option:
Ans. Ovulation and Menstruation
Ques. The given figure shows the different stages of human embryo. Identify the correct labellings for W, X, Y, Z and choose the correct option.
Ans. Morula, Cleavage, Blastocyst, Fertilisation
Ques. During human embryonic development the external genital organs are well developed in the foetus by the end of –
Ans. 12 weeks of pregnancy
Ques. The accessory ducts in the human male reproductive system consists of-
Ans. Rete testis, epididymis, Vas deferns
Ques. Given below is a figure of an angiosperm plant showing two different types of flowers “X” and “Y” the possible type of pollination in them-
Ans. Flower X – Chasmogamous, self/cross pollination; Flower Y – Cleistogamous, self-pollination
Ques. An undifferentiated sheath covering the root cap of a monocotyledonous embryo is-
Ans. Coleorhiza
Ques. The cause of Down’s Syndrome in human is-
Ans. Extra copy of an autosome
Ques. Which of the following features show the mechanism of sex determination in honey-bee-
Ans. ()ii Males have half the number of correct chromosomes than that of a female, (iii) The females are diploid having 32 chroomosomes
Ques. Select the pair that is incorrect-
Ans. Haemophilia – autosome linked recessive trait
Ques. An example of a human trait where a single gene can exhibit multiple phenotypic expression is-
Ans. Phenyl ketonuria
Ques. Life cycle of “Drosophila melanogaster” is completed in-
Ans. 14 days
Ques. How many type of gametes would develop by an organism with genotype AaBBCcDD-
Ans. 4
Ques. Given below are observations drawn in HGP. Select the option that shows the correct observation-
Ans. (iii) Less than 2% of genome code for protein, (iv) Chromosome one has most genes (2698)
Ques. The phosphoester linkage in the formation of a nucleotide involves the bonding between-
Ans. Phosphate group and OH at 3 degree celsius of nucleoside
Ques. The switching “on” and “off” of the lac operon in prokaryotes is regulated by-
Ans. Lactose
Ques. 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-
Ans. Dioxyribonucleotide triphosphate
Ques. Which one of the following factor will associate transiently with RNA polymerase to terminate transcription in prokaryotes-
Ans. RHO factor
Ques. Choose the correct pair of codon with its corresponding amino acid from following list:
Ans. UUU: Phenylalanine
Ques. During elongation process of translation, the peptide bond formation between amino acids is catalysed by-
Ans. ribosomal RNA
Ques. Assertion (A): Through reproductive and child health (RCH) program in India, we could bring down the population growth rate.
Reason (R ): The rapid increase in MMR and IMR were the reasons, along other reasons for this.
Ans. (A) and (R) is true, and (R) is correct explaination of (A)
Ques. Assertion (A): Sterilisation methods are generally advised for male/ female partners as a terminal method to prevent any more pregnancies.
Reason (R ): These techniques are less effective and have high reversibility.
Ans. (A) is true but (R) is false
Ques. 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 get arranged into trophoblast and inner cell mass.
Ans. Both (A) and (R) are true, and (R) is the correct explaination of (A)
Ques. Assertion (A): There is expression of only one gene of the parental character in the Mendelian Monohybrid cross F1 generation.
Reason (R ): In the dissimilar pair of factors one member of the pair dominates the other.
Ans. Both (A) and (R) are true, but (R) is not the correct explaination of (A)
Ques. Select the correct option for Human Chorionic Gonadotropin (HCG) released during embryonic development in humans.
Ans. Helps in maintenance of pregnancy, Brings metabolic changes in mother
Ques. Residual persistent nucellus in black paper is known as-
Ans. Perisperm
Ques. Amongst the insects the dominant biotic pollinating agents are
Ans. Bees
Ques. The source of gonadotropin LH and its corresponding function is
Ans. Anterior pituitary, ovulation
Ques. A specialized procedure to form an embryo in the laboratory in which sperm is directly, injected into the ovum is
Ans. ICSI
Ques. Listed below are all reproductive tract infections except –
Ans. Filariasis
Ques. A genetic mechanism which prevents inbreeding depression in majority of angiospermic plants is
Ans. Self-incompatibility
Ques. Is Pisum sativum, the flower color may be Violet (V) or White (v). What proportion of offsprings in a cross of VV x vv would be expected to be violet?
Ans. 100%
Ques. Which one of the gene pair is expected to give a ratio of 1:1:1 in the progeny of a Mendelian Dihybrid cross?
Ans. AaBb x aabb
Ques. The progeny of a cross between two snap-drag plants heterozygous for flower colour, bearing different coloured flower would be:
Ans. 25% red, 50% pink, 25% white
Ques. A child with a bood group A has father with blood group B and mother with blood group AB. What would be the possible genotypes of parents and child? Choose the correct option.
Ans. correct option is (c)
Ques. In a dihybrid Mendelian cross, garden pea plants heterozygous for violet flowers and round seeds are crossed with homozygous white flowers and wrinkled seeds. The genotypic and phenotypic ratio of F1 progeny would be
Ans. 1:1:1:1
Ques. A region of coding strand in DNA has the following nucleotide sequence: 5′ – TGCGCCA-3′
The sequence of bases of mRNA transcribed by this DNA strand would be:
Ans. 5′ – UGCGCCA – 3′
Ques. A DNA molecule is 160 base pairs long. It has 20% adenine. How many cytosine bases are present in this DNA molecule?
Ans. 96
Ques. A template strand in a bacterial DNA has the following base sequences: 5′ – TTTAACGAGG – 3′. What would be the RNA sequence transcribed from this template DNA?
Ans. Wrong question, bonus marks expected
Ques. 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?
Ans. anticodon loop, clover-leaf
Ques. Which type of RNA is incorrectly paired with its function?
Ans. transfer RNA: attaches to amino acid
FAQs
You can get the answer key at the official website.
The official website of CBSC Board is cbseacademic.nic.in.
No
each correct answer you can add+1, each wrong answer you can deduct -0 in this examination.
You need to visit the official website, hen you can see the answer key. the process to check answer key is given on his page.
In the PDF format you can get the answer key.