CBSE 12TH BIOLOGY - Online Test
Q1. How many sperms are formed by 4 primary spermatocytes?
Answer : Option A
Explaination / Solution:
Each primary spermatocyte undergoes first meiotic division to produce 2 secondary spermatocytes, which further proceeds to second meiotic division to form 2 spermatids. So, each primary spermatocyte produces 4 sperms.
Q2. Deforestation generally decreases
Answer : Option D
Explaination / Solution:
Deforestation generally decreases rainfall. Plants release water in form of water vapour in the process of transpiration. The water vapour contribute in cloud formation to bring rains.
Q3. Which of the following is an example of genetic variation?
Answer : Option B
Explaination / Solution:
Genetic variation is the difference in the offspring of same parents produce sexually. The children of same parents having different eye colour is an example of genetic variation. Age, scar and eating habits are not genetic variation.
Q4. Which one is not a side effect due to regular use of contraceptive methods
Answer : Option C
Explaination / Solution:
Regular use of contraceptive methods may cause some side effects such as abdominal pain, breast cancer and nausea. AIDS is a viral disease caused by HIV and not a side effect of contraceptive method.
Q5. According to the lac-operon concept, which functional unit of the bacterial gene material is responsible for suppressing the activity of the operator gene in the absence of lactose?
Answer : Option D
Explaination / Solution:
A regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator gene (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase). In prokaryotes, regulator genes often code for repressor proteins.
Q6. The developing sperms are nourished by
Answer : Option D
Explaination / Solution:
Seminiferous tubules contain Spermatogonia and Sertoli cells. Spermatogonium undergoes meiotic division to produce sperms and Sertoli cells provide nourishment to them.
Q7. Forest act was first enacted in
Answer : Option B
Explaination / Solution:
An Act to consolidate the law relating to forests, the transit of forest-produce and the duty leviable on timber and other forest-produce. The Indian Forest Act, 1927 was largely based on previous Indian Forest Acts implemented under the British.
Q8. The tendency of population to remain in genetic equilibrium may be disturbed by
Answer : Option C
Explaination / Solution:
The tendency of population to remain in genetic equilibrium may be disturbed by lack of random mating due to ethics and geographical or other barriers.
Q9. Vasectomy is a surgical method of birth control performed in
Answer : Option B
Explaination / Solution:
Vasectomy is surgical method of birth control in male in which vas deference is cut and tides to prevent release of sperm during coitus. This method cannot be reversed back.
Q10. Removal of introns and joining of exons in a defined order during transcription is called
Answer : Option C
Explaination / Solution:
The mRNA produced by transcription of DNA consists of exons and introns. The removal of introns and joining of exons to obtain mature mRNA is called splicing. It is followed by capping and tailing.
