Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance4 Marks
Question
Read the following and answer any four questions from (i) to (v) given below:

Mutation explains the relationship between gene and DNA. The effects of large deletions and rearrangement in a segment of DNA results in loss or gain of gene and its function. Insertion or deletion of one or two bases changes the reading frame from the point of insertion or deletion. A classical example of point mutation is a change of single base pair in the gene for beta globin chain that results in change of amino acid residue glutamate to valine and results into a diseased condition called sickle cell anaemia.

  1. A mutation is a change produced by an alteration in the genetic mechanism and.
  1. May arise spontaneously.
  2. Is always induced by the environment.
  3. Is never advantageous.
  4. Is not inherited.
  1. The DNA code for glutamic acid is CTC or CTT. The code for valine is CAA or CAT. In sickle cell haemoglobin, valine is present instead of glutamic acid.

Assuming a single base pair substitution has occurred, what is the mRNA code in the affected mutant?

  1. CUU
  2. GAA
  3. GAG
  4. GUA
  1. A mutation involving the substitution of one nitrogenous base for another has altered the base sequence of a DNA molecule, coding for four amino acids, as shown below.

Normal A-G-C-A-T-G-G-A-T-C-C-T

Mutant A-G-C-A-T-G-C-A-T-C-C-T

The table shows six codons and the corresponding amino acids into which each is translated.

mRNA codon
Amino acid
AAG
Lysine
CUA
Leucine
GGA
Glycine
GUA
Valine
UAC
Tyrosine
UCG
Serine
The mutation has changed the amino acid.

  1. Leucine to valine.
  2. Lysine to glycine.
  3. Serine to leucine.
  4. Tyrosine to lysine.
  1. Assertion : Insertion or deletion of three or its multiple bases, insert or delete one or multiple codons and so one or multiple amino acids.

Reason: Reading frame remains unaltered with insertion or deletion of three or its multiple bases.

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
  1. Part of the amino acid sequences in normal and sickle cell haemoglobin are shown.
Normal haemoglobin Sickle cell haemoglobin
Thr-Pro-Glu-Glu Thr-Pro-Val-Glu
mRNA codons for these amino acids are

Glutamine (Glu) GAA GAG

Praline (Pro) CCU CCC

Threonine (Thr) ACU ACC

Valine (Val) GUA GUG

Which transfer RNA molecule is involved in the formation of this part of the sickle cell haemoglobin?

✓

Answer

  1. (a) May arise spontaneously.

Explanation:

A mutation is a change in the DNA that changes the physiological effect of the DNA on the cell. Such phenomenon may be caused by radiation, chemical carcinogens, or may occur spontaneously.

  1. (d) GUA

Explanation:

Since a single base pair substitution has caused this mutation, the original codon for glutamic acid must have been CTT, and the mutant codon is CAT. The mRNA code for this mutant is hence GUA, i.e., complementary to CAT.

  1. (a) Leucine to valine.

Explanation:

The segment coding for GAT on the normal DNA molecule has been transcribed into CUA in the mRNA molecule, therefore the mutant DNA strand CAT will be transcribed into GUA on the mRNA molecule. This implies a change from the amino acid leucine to valine.

  1. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion.
  2. (b) 

Explanation:

CAU in tRNA is the only one that can compliment the valine in the sickle cell haemoglobin.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Case study (4 Marks)" from Molecular Basis of Inheritance→Molecular Basis of Inheritance — all question types→BIOLOGY STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

Describe: Genetic engineered insulin
→
Read the following and answer any four questions from (i) to (v) given below:
The Kakapo is the world's largest and heaviest parrot, found only in New Zealand. It is unusual in that it is nocturnal, flightless and ground-dwelling. It is an excellent climber of trees, has strong legs that allow it to "jog" several kilometres in a single trip, and has mossy green plumage mottled with brown and yellow. The Kakapo is also critically endangered as of now, there were only few known living individuals left.
  1. Which could be the possible reason for Kakapo to be well-adapted to its environment prior to the arrival of humans in New Zealand?
  1. Kakapo was active only in the night when its potential predators would not be out for hunting.
  2. The Kakapo would likely be well-camouflaged among the forest foliage due to its greenish plumage.
  3. It was able to effectively hunt for food in the night.
  4. All of these.
  1. When humans started to settle in New Zealand, they took with them non-native animals, including mammals such as cats, dogs and stoats. By which of the following ways, human settlement likely contributed to a near decimation of Kakapo populations in New Zealand?
  1. Habitat destruction.
  2. Alien species invasion.
  3. Pollution.
  4. Both (a) and (b).
  1. All known survived Kakapo have been relocated by the New Zealand government to three predator-free islands, where they are monitored year round by staffs and volunteers to ensure that the birds are safe, healthy and well-fed. The extremely low population of Kakapo is a hurdle to the species becoming viable in the long term, despite such dedicated conservation efforts. This is because.
  1. The small population results in very small gene pool.
  2. There would be very Ii mited genetic diversity among the resulting offspring.
  3. Of reduced capacity of the species to adapt and survive changes in the environment.
  4. All of these.
  1. The reasons behind conserving biodiversity have been grouped into which of the following categories?
  1. Narrowly utilitarian.
  2. Broadly utilitarian.
  3. Ethical.
  4. All of these.
  1. One of the ex situ conservation methods for endangered species is:
  1. Wildlife sanctuaries.
  2. Biosphere reserves.
  3. Cryopreservation.
  4. National parks.
→
Read the following and answer any four questions from (i) to (v) given below:
Disposal of untreated sewage into the river or freshwater pond causes huge water pollution. Four water samples from different sources (A, B, C, D) are collected and tested for BOD value in a lab to assess their quality. The BOD values are presented in the given table. Water samples are collected from primary effluent, secondary effluent, untreated sewage and river water. Study the given table and answer the following.
Sample BOD
A 20mg/ L
B 5mg/ L
C 300mg/ L
D 400mg/ L
  1. The source of sample 'C' is:
  1. River water.
  2. Primary effluent.
  3. Secondary effluent.
  4. Untreated sewage water.
  1. If sewage in untreated condition is disposed off in a freshwater body then.
  1. BOD and dissolved oxygen both will increase.
  2. BOD will increase and dissolved oxygen will decreas.
  3. BOD will decrease and dissolved oxygen will increase.
  4. BOD and dissolved oxygen both will decrease.
  1. A large number of pathogenic microbes can be present in water sample of:
  1. C
  2. A
  3. D
  4. Both (a) and (c).
  1. High value of BOD in sample O is due to:
  1. High amount of organic wastes and aerobic microbes.
  2. High amount of inorganic wastes and anaerobic microbes.
  3. High amount of organic wastes and anaerobic microbes.
  4. High amount of inorganic wastes and aerobic microbes.
  1. River water is represented by the sample.
  1. A
  2. B
  3. C
  4. D
→
Give information about primary and secondary lymphoid organ ### Explain lymphatic organs of human lymphatic system. (Diagram is not required)
→
Write a short note on embryo development.###With a labeled diagram discuss stages in embryo development in a dicot.
→
Match the terms in Column I with those in Column II.
S. No Column I S. No Column II
(i) Gene therapy 1. Human insulin.
(ii) Cotton bollworm 2. Biopiracy.
(iii) Eli Lilly 3. Emphysema.
(iv) Basmati Rice 4. ADA deficiency.
(v) $\alpha-1\text{ antitrypsin}$ 5. Lepidopteran.
→
Read the following text carefully and answer the questions that follow:
A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes. The immune system of a person is suppressed. He was found positive for a pathogen in the diagnostic test ELISA.
Image
i. Name the disease, the patient is suffering from. (1)
ii. Which pathogen is identified by ELISA test? (1)
iii. Which cells of the body are attacked by the pathogen? (2)
OR
Suggest preventive measures of the infection. (2)
→
Write a short note on pollination by wind.
→
Read the following and answer any four questions from (i) to (v) given below:

During teaching about various environmental factors, a teacher draw a figure that depicts like history strategies for three plant species (X, Y and Z) along 3 axes - strength of competition with other organisms, level of disturbance in the habitat and level of environmental stress in the habitat. Species X grows in habitats where competition among species is high but disturbance and stress are low. Species Y grows in habitats with high environmental stress but with low intraspecies competition. Species Z grows in highly disturbed habitats with low environmental stress.

  1. Which of the following is correct regarding plant type X?
  1. It has slow growth rate.
  2. It lives in area with high probability of severe environmental changes.
  3. It has good competitive ability at low population densities near the carrying capacity.
  4. None of these.
  1. Environmental stress occurs through.
  1. Very low temperature.
  2. Drought.
  3. Nutrient deficiency.
  4. All of these.
  1. Select the correct option regarding plant type X, Y and Z.
  1. X type of plants are likely to be trees.
  2. Y type of plants could be desert plants.
  3. Z type of plants could be herbaceous plant.
  4. All of these.
  1. Y type of plants grow under high stress and:
  1. Produce large number of seeds in a short time after rains.
  2. Have rapid growth.
  3. Produce less number of seed in a long time after rain.
  4. Both (a) and (b).
  1. Assertion: Plant growth rate is high in area of high stress and high disturbance.

Reason: High stress and high disturbance promote breeding capacity in plants.

  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
→
Differentiate between following.
→