CBSE 12TH BIOLOGY - Online Test
Q1. Self-pollination is transfer of pollen from anther to stigma of
Answer : Option B
Explaination / Solution:
The transfer of pollen grain from anther to stigma of same flower is called self-pollination. Both anther and stigma must be ready at same time for this kind of pollination.
Q2. A metastatic cancerous tissue is termed ‘sarcoma’ if the disorder is in
Answer : Option A
Explaination / Solution:
A metastatic cancerous tissue is called sarcoma if the disorder is in fibroblast. The property of cancerous cells to reach from one part of the body to other through blood is called metastasis.
Q3. A gene of operon which synthesizes a repressor protein is
Answer : Option C
Explaination / Solution:
No Explaination.
Q4. Large proportion of cultivated plants are
Answer : Option A
Explaination / Solution:
Cultivated plants are mostly allopolyploids that contain multiple sets of genetic material in their cells. Bread wheat is generally hexaploid. Allopolyploids occurs due to faulty karyokinesis.
Q5. Endemics of western Ghats include
Answer : Option B
Explaination / Solution:
Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type.
Notable endemics are the Nilgiri leaf monkey and the brown and carmine Beddome's toad of the Western Ghats.
Q6. In the human, sperm contain 22 pairs of autosomes and
Answer : Option A
Explaination / Solution:
An egg or sperm only has half of the parent's sex chromosome pair. An egg will always have an X chromosome, since the woman's sex chromosome pair only has Xs. Sperm can have either an X chromosome or a Y chromosome. If Y-chromosome containing sperm fertilize the ovum results is male.
Q7. Henking X-body present in 50% of sperms are now known as
Answer : Option B
Explaination / Solution:
Henking trace a specific structure in 50% of sperms. He gave the name x-body to this structure but he was not able to explain the significance of this structure. Further, investigation revealed that x-body was a chromosome, called X-chromosome.
Q8. Crop rotation is used by farmers to increase
Answer : Option A
Explaination / Solution:
Crop rotation is the method of agriculture in which leguminous plants are grown between two cereal crops. The root nodule of these bacterium fix the atmospheric nitrogen and increase the fertility of soil.
Q9. In certain parts of India, forests are burnt and the ash is mixed with the soil and the land used forcultivation leads to deforestation and this process is named as
Answer : Option D
Explaination / Solution:
Shifting cultivation is a kind of cultivation in which cultivating land is changed periodically. Forests are burnt and the ash is mixed with the soil and the land is used for cultivation of crop. This kind of cultivation causes deforestation.
Q10. How bacterial cells protect themselves from the action of their own restriction enzymes?
Answer : Option D
Explaination / Solution:
The protection is offered by the action of the methylase. The methylase recognizes the same target site as the restriction enzyme and adds a methyl group to a specific nucleotide in the restriction site. Methylated sites are not substrates for the restriction enzyme.
The bacterial DNA is methylated immediately following replication so it will not be a suitable substrate for restriction endonuclease cleavage.
Thus, the viral DNA is restricted in the bacterial cell by the restriction enzyme, and the bacterial DNA is modified by the methylase and is provided protection.
