Biology Board Sample Paper 2023-2024 Science (English Medium) Class 12 Question Paper Solution

Remnants of nucellus are persistent during seed development in ______.

pea

groundnut

wheat

black pepper

The wall layer of microsporangium, which nourishes the pollen grain, is ______.

epidermis

endothecium

middle layers

tapetum

A short piece of DNA, having 20 base pairs, was analyzed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown in the table.

How many nucleotides containing Adenine were present in strand 2?

2

4

5

7

In a certain species of insects, some have 13 chromosomes, and others have 14 chromosomes. The 13 and 14 chromosome-bearing organisms are ______.

males and females, respectively

females and males, respectively

all males

all females

At a particular locus, the frequency of allele A is 0.8, and that of allele a is 0.2. What would be the frequency of heterozygotes in a random mating population at equilibrium?

0.32

0.16

0.24

0.48

Variations caused due to mutations are ______.

random and directionless

random and directional

random and small

random, small and directional

What is the smallest part of a DNA molecule that can be changed by a point mutation?

Oligonucleotide

Codon

Gene

Nucleotide

What should be the genotype of the indicated member?

AA

Aa

XY

aa

A patient was advised to have a kidney transplant. To suppress the immune reaction, the doctor would administer him ______.

statins produced from Monascus purpureus

statins produced from Streptococcus thermophilus

cyclosporin A produced from Trichoderma polysporum

cyclosporin A produced from Clostridium butylicum

Identify the activity of endonuclease and exonuclease in the given image.

The main objective of the production of pest-resistant GM crops is to ______.

Encourage eco-friendly pesticides.

reduce pesticide accumulation in the food chain.

eliminate pests from the field without the use of manual labour.

retain maximum nutritional content in the crop that would be otherwise consumed by pests.

Observe the contents 1, 2, 3 and 4 of soil samples A, B and C shown in the graph. If the temperature and soil moisture of all soil samples are identical, which soil sample (s) will show faster decomposition?

1 indicates lignin content, 2 indicates chitin, 3 indicates nitrogen content, and 4 indicates sugar content

Soil Sample A

Soil Sample B

Soil Samples A and B both

Soil Sample C

• Assertion: Primary endosperm nucleus is diploid.
• Reason: It is the product of double fertilisation.

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

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

A is true but R is false.

A is false but R is true.

• Assertion: Ribosomal RNA is synthesized in the nucleus of the cell.
• Reason: It is translated with the enzyme RNA polymerase III.

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

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

A is true but R is false.

A is false but R is true.

• Assertion: Smoking can raise blood pressure and increase heart rate.
• Reason: Nicotine stimulates adrenal glands to release adrenaline and noradrenaline into the blood circulation, both of which raise blood pressure and increase heart rate.

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

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

A is true but R is false.

A is false but R is true.

• Assertion: PCR is a powerful technique to identify genetic disorders.
• Reason: PCR can detect mutations in low amounts of DNA.

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

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

A is true but R is false.

A is false but R is true.

Explain the process of hormonal regulation of spermatogenesis.

The diagram below shows the sequence of amino acids in part of a haemoglobin molecule.

1. If the base T* was substituted with A, how would it affect the haemoglobin chain?
2. Name the condition and the effects associated with the above substitution.

The graph given below indicates the administration of the first (L) and second dose (M) of a vaccine. The corresponding response of the body is indicated by X, and Y. Interpret the graph and explain the reason for such a response shown by the body.

The image below shows the result of plating bacteria in a chromogenic medium after incorporating the gene of interest in the plasmid. Some plates had blue colonies; some plates had white colonies. A single bacterium extracted from Plate I, II, and III is shown below:

On the basis of your observations:

1. Identify the plate(s) which is/are white. Give a reason.
2. Identify the plate(s) which is/are blue. Give a reason.

The biomass of a standing crop of phytoplankton is 4 kg/m², which supports a large standing crop of zooplankton having a biomass of 11 kg/m². This is consumed by small fishes having a biomass of 25 kg/m², which are then consumed by large fishes with a biomass of 37 kg/m².

Draw an ecological pyramid indicating the biomass at each stage and also name the trophic levels. Mention whether it is an upright or inverted pyramid.

Use the information provided in the table given below to answer the following questions:

1. Calculate the gross primary productivity.
2. Analyze the trend in the Net Production from Producers to Top Carnivore. Give a reason for your observation.

The figure given below shows 3 sperms A, B and C.

1. Which one of the three sperms will gain entry into the ovum?
2. Describe the associated changes induced by it on P and Q.

Ovum surrounded by few sperms

Explain the phases in embryonic development from the morula stage till the establishment of pregnancy in a human female.

A pregnant human female was advised to undergo MTP. It was diagnosed that the fetus she was carrying had developed from a zygote having 45 chromosomes with only one X chromosome.

1. What is this condition called and how does it arise?
2. Why was she advised to undergo MTP?

The graphs below show three types of natural selection. The shaded areas marked with arrows show the individuals in the population who are not selected. The dotted vertical lines show the statistical means.

character Graph A	character Graph B	character Graph C

1. What names are given to the types of selection shown in graphs A, B and C?
2. After the selection has operated for several generations in the above populations indicated as, Graph A, B and C, graphically illustrate the probable results.

The aeration tank of a sewage treatment plant is not functioning properly. Explain in detail the impact of this on the treatment of sewage and BOD of the effluent.

A farmer grew 2 varieties of corn crops in fields A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed corn borers attacked only in field A. To control it, spores of Bt were sprayed in field A.

1. Name the gene in the spores responsible for the control of this pest.
2. What effect will the spores of Bt have on the insect pest?
3. How has field B developed resistance against this pest?

Lipoprotein lipase deficiency (LPLD)is a genetic disorder in which a person has a defective gene for lipase. This leads to high triglycerides, stomach pain, and fat deposits under the skin. It may eventually affect the liver, pancreas and may also cause diabetes. The disorder occurs if a child acquires defective genes from both parents (autosomal recessive). ERT (enzyme replacement treatment) is one of the treatments offered to patients with LPLD.

1. 1. What procedure is followed in ERT?
   2. What could be one possible drawback of ERT?
2. How can LPLD be treated using Biotechnology? Elaborate.

Give three reasons as to why the prokaryotes are not given any figures for their diversity by ecologists.

The structure below shows pUC18, which is similar to pBR322 in its function. However, they differ in some of their restriction sites and the number of ori. The ori number for pBR322 is approximately 20.

1. How are puc18 and pBR322 used in biotechnological studies?
   OR
   What will be the impact if the ori in the above structure gets damaged?
2. The lac z gene has many recognition sites. Study the segment of DNA given below and answer the questions.
   5’... ATC GTA AAG CTT CAT…3’
   3’... TAG CAT TTC GAA GTA…5’
   i) Applying your knowledge of palindrome sequences identify and mark the possible region where the restriction enzyme X will act.
   ii) Restriction enzyme Y was used to extract a gene of interest from a plant. This gene needs to be inserted in the given DNA segment which has been treated with restriction enzyme X. Will there be a successful recombination? Explain with a reason.
3. Which one of the two (pUC18 and pBR322) would you prefer for biotechnological studies? Justify.

Observe the graph given below.

a) Which species is competitively superior? Support it with the data provided in the graph.

b) State the underlying principle for the above result and name the scientist associated with this principle.

c) Explain the mechanism in which two or more species competing with each other can co-exist.

OR

Graphs A and B shown below depict interaction of two species. Which graph indicates Mutualism? Give reason.

A	B

Placed below are case studies of some couples who were not able to have kids. These couples are not ready for adoption or taking gametes from donors. After thoroughly examining the cases, which Assisted Reproductive Technology will you suggest to these couples as a medical expert? Explain briefly with justification of each case.

Given below are certain situations. Analyse the situation and suggest the name of suitable contraceptive device along with mode of action.

Given below is a stretch of DNA showing the coding strand of a structural gene of a transcription unit?

5’-ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TAA-3’

1. Write the corresponding template strand and the mRNA strand that will be transcribed, along with its polarity.
2. If GUA of the transcribed mRNA is an intron, depict the sequence involved in the formation of mRNA/the mature processed hnRNA strand.
   i. In a bacterium
   ii. In humans
3. Upon translation, how many amino acids will the resulting polypeptide have? Justify.

In shorthorn cattle, the coat colours red or white are controlled by a single pair of alleles. A calf which receives the allele for red coat from its mother and the allele for white coat from its father is called a 'roan'. It has an equal number of red and white hairs in its coat.

1. Is this an example of codominance or of incomplete dominance?
2. Give a reason for your answer.
3. With the help of genetic cross explain what will be the consequent phenotype of the calf when,
   
   1. red is dominant over white.
   2. red is incompletely dominant.

Explain the role of Primary and Secondary Lymphoid organs with the help of suitable examples.

With the help of a flow chart, illustrate how an infected animal cell can survive while viruses are being replicated or released.