Biology Delhi Set 2 2024-2025 Science (English Medium) Class 12 Question Paper Solution

Mohit performed an analysis of two different soil samples from two areas A and B. He recorded these results:

Soil Sample A: Lignin 40%, Sugar 10%, Chitin 45%, Nitrogen 5%

Soil Sample B: Lignin 5%, Sugar 35%, Chitin 15%, Nitrogen 45%

Which of these is true about their rate of decomposition in both the soil?

Soil A has a slower rate of decomposition than Soil B.

Soil A has a faster rate of decomposition than Soil B.

Both have the same rate of decomposition.

No decomposition occurs in A and B.

Diameter of the pollen grain generally is ______.

5 to 10 micrometer

10 to 15 micrometer

25 to 50 micrometer

50 to 100 micrometer

Menstrual cycle in human females consists of various events.

Select the option that indicates the correct sequence of these events of menstrual cycle.

Menstrual phase, Follicular phase, Luteal phase, Ovulatory phase

Luteal phase, Follicular phase, Ovulatory phase, Menstrual phase

Menstrual phase, Follicular phase, Ovulatory phase, Luteal phase

Follicular phase, Luteal phase, Menstrual phase, Ovulatory phase

A Dihybrid cross is done between two parent pea plants (pure line) who differ in two pairs of contrasting traits: Seed colour and seed shape.

In the F₂ generation the number of phenotypes and genotypes will be:

phenotypes = 4; genotypes = 16

phenotypes = 9; genotypes = 14

phenotypes = 4; genotypes = 8

phenotypes = 4; genotypes = 9

RNA interference (RNAi) helps in making tobacco-plant resistant to a nematode (Meloidegyne incognitia)

Choose the correct option that shows how RNAi is achieved:

Preventing the process of translation of mRNA of the nematode.

Preventing the process of replication of DNA of the nematode.

Preventing the process of transcription of DNA of the plant.

Preventing the process of replication of DNA of the plant.

The sequence of nitrogenous bases in a segment of a coding strand of DNA is 5'-AATGCTAGGCAC-3'.

Choose the option that shows the correct sequence of nitrogenous bases in the mRNA transcribed by the DNA.

5'-UUACGAACCGAG-3'

5'-AAUGCUAGGCAC-3'

5'-UUACGUACCGUG-3'

5'-AACGUAGGCAGC-3'

A man whose father was colour-blind marries a woman who had a colour- blind mother and a normal father. What percentage of the male children of this couple will be colour-blind?

25%

0%

50%

75%

Evolution of modern man involves the following man-like primates.

Choose the correct series of human evolution.

Dryopithecus → Homo erectus → Australopithecines → Homo sapiens

Australopithecines → Homo erectus → Neanderthal → Homo sapiens

Australopithecines → Ramapithecus → Dryopithecus → Homo sapiens

Homo erectus → Australopithecines → Homo sapiens → Neanderthal

GEAC stands for ______.

Genome Engineering Action Committee

Ground Environment Action Committee

Genetic Engineering Approval Committee

Genetic and Environment Approval Committee

Transplantation of tissues/organs to save certain patients often fails due to rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?

Auto-immune response

Humoral immune response

Physiological immune response

Cell-mediated immune response

Amplification of gene of interest by using DNA polymerase may go upto ______.

0.1 million times

1 million times

1 billion times

1 trillion times

The diagram given below shows labelling of four parts of a dicot embryo during its development as P, Q, R and S.

Choose the option that indicates correct labelling of ‘P’, ‘Q’, ‘R’ and ‘S’ of embryo in different stages of its development:

P - Egg, Q - Suspensor, R - Radicle, S - Cotyledon

P - Zygote, Q - Suspensor, R - Cotyledon, S - Plumule

P - Egg, Q - Radicle, R - Suspensor, S - Cotyledon

P - Zygote, Q - Suspensor, R - Cotyledon, S - Radicle

Assertion (A): Perisperm is a diploid tissue.

Reason (R): Perisperm is the remains of nucellus which surrounds the embryo in certain seeds.

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

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(A) is true, but (R) is false.

(A) is false, but (R) is true.

Assertion (A): While working on Staphylococci, Alexander Fleming observed that Penicillium notatum inhibits the growth of bacteria.

Reason (R): The inhibiting chemical was commercially extracted and its full potential was established by Alexander Fleming.

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

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(A) is true, but (R) is false.

(A) is false, but (R) is true.

Assertion (A): One of the property of genetic code is degeneracy. 

Reason (R): Some amino acids can be coded by more than one codon.

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

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(A) is true, but (R) is false.

(A) is false, but (R) is true.

Assertion (A): A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions.

Reason (R): The most commonly used bioreactors are of stirring type.

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

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(A) is true, but (R) is false.

(A) is false, but (R) is true.

Study the two different crosses given below:

Identify the abnormalities 1 and 2 in the offsprings of given crosses and distinguish between them.

Study the pedigree analysis of Myotonic dystrophy given below:

Answer the following questions:

1. Write genotype of A, B, C and D.
2. Identify whether the trait is
   1. Sex linked or autosomal
   2. Dominant or recessive

A patient with ADA deficiency requires periodic infusion of genetically engineered lymphocytes. Explain why such periodic infusion is required and also suggest a permanent cure for such ADA deficiency.

Describe in brief any two techniques that can be utilised to transfer recombinant DNA into the host cell directly without using any vector.

How are morphine and heroin related?

Mention the effect of morphine and heroin on the human body.

Name an alcoholic drink which is produced by the help of microbes with distillation.

Name an alcoholic drink which is produced by the help of microbes without distillation.

Explain how cyanobacteria can be used as a bio-fertilizer.

Analyse the following ecosystems and discuss, which will be more productive in terms of primary productivity:

A young forest, a natural old forest, a shallow polluted lake.

Differentiate between gross primary productivity and net primary productivity.

Explain the importance of ‘ori’ and ‘rop’ in the E. coli cloning vector shown in the above given diagram.

Distinguish between exonuclease and endonuclease.

The great German naturalist and geographer Alexander Von Humboldt observed that within a region species richness increased with increasing explored area, but only upto a limit.

1. For the above situation, construct a graph and write an equation.
2. Also write various values of Z (regression coefficient).

Shyam and Radha are expecting their first child with Radha being in her second month of pregnancy with no complications. Shyam’s family has a history of cystic fibrosis while Radha’s family has a history of Down’s syndrome, leading to a concern that the baby may have one of these conditions.

1. Suggest and explain a way of testing if their baby is at risk for any genetic disorders.
2. In case of presence of one or both of the abnormalities and posing a risk to the mother’s health, mention one possible option for them to consider. Is that option safe for Radha at the current gestational age? Justify.
3. Under what conditions is the process mentioned in (b) illegal?

Write the palindromic nucleotide sequence for the following sequence of DNA segment:

5'-GAATTC-3'

Name the restriction endonuclease that recognizes the 5'-GAATTC-3' sequence.

How are sticky ends produced?

Mention the role of sticky ends.

Study a part of life cycle of Plasmodium given below: 

Answer the following questions:

1. Name the infective stage of Plasmodium that is stored in the female Anopheles mosquito.
2. Where does fertilization and development of parasite take place?
3. Identify labels P and Q in the given diagram.
4. Asexual and sexual phase of the life cycle of the Plasmodium takes place in two different hosts. Write their names.

Compare and contrast convergent and divergent evolution.

Study the diagram given below and answer the questions that follows:

1. Identify the structure shown in the above figure.
2. Identify the labels P and Q.
3. Write the nature of histone proteins.
4. Distinguish between Euchromatin and Heterochromatin.

Read the following passage and answer the questions that follow:

1. The Monarch butterfly is highly distasteful to its predator because of a special chemical present in its body. How does the butterfly acquire this chemical?
2. If population density at a time t + 1 is 800, Emigration = 100, Immigration = 200, Natality = 200 and Mortality = 150, calculate the population density at time t and comment upon the type of age pyramid that will be formed in this case.
3. What is the difference in a method of measuring population density in an area if there are 200 carrot grass plants to only single huge banyan tree?
   OR
4. Name two methods to measure the population density of tigers.

Study the graphs given below for Case 1 and Case 2 showing different levels of certain hormones and answer the question that follows:

1. Which hormone is responsible for the peak observed in Case 1 and Case 2? Write one function of that hormone.
2. Write changes that take place in the ovary and uterus during follicular phase.
3. Name the hormone Q of Case 2. Write one function of hormone Q.
   OR
4. Which structure in the ovary will remain functional in Case 2? How is it formed?

Distinguish between the two cells enclosed in a mature male gametophyte of an angiosperm.

Study the diagram given below showing the modes of pollination. Answer the questions that follow.

1. The given diagram shows three methods of pollen transfer in plants. Examine them carefully and write the technical terms used for pollen transfer methods ‘1’, ‘2’, and ‘3’.
2. How do the following plants achieve pollination successfully?
   1. Water lily
   2. Vallisneria
3. Write the advantages of pollen transfer in method ‘3’.

Given below is the diagram of human ovum surrounded by a few sperms. Observe the diagram and answer the questions that follows:

1. Compare the fate of sperms ‘P’, ‘Q’ and ‘R’ shown in the diagram.
2. Write the role of Zona pellucida in this process.
3. Analyse the changes occurring in the ovum after the entry of sperm.
4. How acrosome and middle piece of a human sperm are able to play an important role in human fertilization?

State what do you understand by “MALT”? Where it is located inside our body?

Explain cytokine barriers.

Name the diagnostic test for AIDS. On what principle does it work?

Bone marrow plays an important role in the human immune system. Explain how it is able to achieve this.

Thymus plays an important role in the human immune system. Explain how it is able to achieve this.

Study the following table & fill ‘H’, ‘I’, ‘J’, ‘K’, ‘L’ and ‘M’ in the following table with suitable words:

Why are baculoviruses considered good biocontrol agents?

Haemophilia and red green colourblindness is usually observed in men. Why?

Perform a cross(es) where haemophilic daughter(s) and haemophilic son(s) are produced in same ratio.

Where do transcription and translation occur in bacteria?

Where do transcription and translation occur in eukaryotes?

Draw neat and labelled diagram of Replication Fork.

A DNA segment has a total of 1000 nucleotides, out of which 240 of them are adenine containing nucleotides. How many pyrimidine bases this DNA segment possesses?