CBSE Class 12 Biotechnology Question Paper 2019 Solutions

MARKING SCHEME

SUBJECT : BIOTECHNOLOGY THEORY (045)

SESSION: 2018-19

SERIES : BVM

QUES SUB VALUE POINTS MARKS
NO PART

1 Converts mRNA into cDNA 1
OR
Polylinker provides flexibility in the choice and use of restriction enzymes.

2 Macerozyme dissolves the middle lamella between the cells to release 1
single cells.
OR
Ethylene Gas
3 Purine/ G or A/Arginine 1

4 Transfer of rDNA into host cells, using charged substances like cationic 1
liposomes.

5 Complex medium/ Luria Broth/ Nutrient Broth/ Trypticase Soy Broth. 1

6 Van der Waals Forces 1

7 Nerve gas alkylates active serine in the brain enzyme acetyl choline 2
esterase inactivating it and leading to death.

8 Primary Metabolites Secondary Metabolites 1+1
 Chemicals that are  Function is not clear but
required for plant basic they are used in defense
metabolic processes. mechanism against pests
 Eg. sugars, lipids, amino and pathogens.
acids, nucleic acid.  Eg Alkaloids, resins,
tannin, latex.
Pg.119

OR
Intergeneric crosses are between distantly related plants which result in
abnormal development of the endosperm causing premature death of
embryo.

9 Golden rice is a transgenic plant in which three genes have been 2
introduced which are involved in the biosynthetic pathway for carotenoid
production. It is enriched in provitamin A ( Beta carotenoids)
10 OKT3 acts by blocking the function of Tcells by binding to the CD3 cell 2
surface receptors.
OR
tPA is a serine protease that catalyzes the dissolution of blood clots.

11 Optimum pH is important for maintaining appropriate ion balance, 2
maintaining optimal function of biomolecules.

12 Programs scan the first 20 symbols. If the symbols switch between A, T, 2
G, C then it is DNA. If instead of T we have U then it is RNA sequence.
If the symbols switch between more than 4 to 6 letters then it is a protein
sequence.
13 [M+nH]n+ 1
[M+5H]5+ m/z = 20005/5 = 4001 ½
[M+4H]4+ m/z = 20004/4 = 5001 ½
14  Post transcriptional modification like polyadenylation / mRNA 1
editing. This could lead to the generation of various proteins
from a single gene.
 Proteins after synthesis could undergo Post translational 1
modifications.
OR
Provide snapshotsof all genes expressedin a cell under different
environmental conditions.
15 A Subtilisin 1
B Due to oxidation of methionine at position 222. 1
C Engineered enzyme has alanine in place of methionine at position 222. 1
16 Page 100. Fig 10 3
OR
Page 106, any 3
17 DNA is extracted from sample of soil, water or other environmental niche 3
and subjected to restriction digestion. Clones are screened for novel
molecules.

18 Batch Culture Continuous Culture 3
1. None of the nutrients are 1. One nutrient in medium
limited. is limited.
2. All phases of growth can 2.Extended Log phase.
be seen
3. Maximum Cell density is 3.Maximum Cell density and
achieved. yield of products are
achieved.
4. Closed culture Open culture
Any three points Or Graph for each culture page 91,92
OR
A Aeration /to improve oxygen transfer 1
B Provides hinderance to diffusion of air and denaturation of protein. 1
C For mutagenesis to generate mutants for strain selection 1

19 Crude homogenate(cell)added to biphasic mixture of dextran and PEG. 3
PEG is soluble constituent of cell homogenate.
Dextran is cellular debris, nucleic acid by nucleases and lipid by using
glass wool.
Page 42
20 A
5’ A G C T 3’ Blunt End - Alu I 1
5’ T C G A 5’

B 5’ G A A T T C 3’ Sticky End- EcoR I 1
5’ C T T A A G 5’

c Sticky ends can base pair and help ligation. Table 1 page 5 1

21 Southern Hybridisation technique page 20 , figure 10 3
OR
Page 9 , figure 4(a & c)
As YEp can be propagated in both prokaryotic (E.coli) and eukaryotic 2+1
(Yeast) hosts therefore it is called a shuttle vector.
22 Transformation, transfection, electroporation, microinjection, biolistic, 3
vectors (explanation of any three) page 14-15

23 Ref Seq: Ref Seq is a curated database of mRNA and proteins of humans, 1
mouse, rat.
Homologues: Similarity due to common ancestry and have same 1
function.
Paralogs : Duplicated Genes within a genome may have similarties but 1
may differ in functions.
OR
BLAST: Basic Local Alignment Search Tool 1
A given sequence is compared with sequences in databases. Top scoring
matches are ranked accordingly to set criteria that serve to distinguish

between similarity due to ancestral relationships or due to random
chance. True matches are further examined thoroughly with other details 2
accessible through ENTREZ and other tools.

24 Page 80 table 6(any 3) 3

25 Splice Variants, overlapping genes, Repeated Sequence and gaps 3
between genome. Number of genes are not related to complexity of
organisms. Page 61
26 A Can divide mitotically and differentiate into specialized cell types. 1½
B Pleuripotent can differentiate into all types of specialized cells and ½ +½ +1
multipotent into limited no. of cells, lineage restricted.
Multipotent, by maintaining normal turnover of regenerative organs like
blood, skin etc. 1½
C Leukemia, heart disease, paralysis, spinal cord injury, burns.
(any three)
OR
1
A Gene knock out- selectively remove a gene. 2
B Used to understand genetic basis of diseases, new diagnostic and
therapeutic modalities. 2
C James Thomson inner cell mass of blastocyst.
27  Collect leaf disc/embryo callus ½x6=3
 Infect with disarmed Ti containing Agrobacterium
 Infected Tissue cultured on shoot regeneration medium for 2-3
days to transfer T-DNA along with foreign gene.
 Transformed tissue, transfer to selection cum plant regeneration
medium having lethal concentration of kanamycin.
 After 3-5 weeks, regenerated transformed shoot are transferred
to root inducing medium.
 After another 3-4 weeks complete plants are transferred to field
for hardening.

By looking for the desired trait in the transgenic plant
(morphological or DNA marker) 1
Diagram page no 122 1
OR

A Edible vaccine- genes and encoding antigen, proteins are isolated and 2
expressed in parts of edible plants such as fruits which can be eaten raw.
B  No storage problem 3
 Easy Delivery System
 Low Cost
 Painless Delivery System
Any three as on page 130

28 A Proteins which have nutritive and pharmaceutical value. 2
B It is a good source of beneficial bacteria and helps in Intestinal function. 1
C Whey protein elevates the tripeptide glutathione which can treat a 1
spectrum of illnesses.
D Meat , sausages, cake and bread (any 1) 1