Biology:2016:CBSE:[Delhi]:Set-III
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Q1
State a difference between a gene and an allele.
Marks:1View AnswerAnswer:
Gene
Allele
A gene is the unit of inheritance that is transferred from the parent to the offspring. It controls the expression of a character. A gene is a linear piece of DNA.
Allele is an alternative form of a gene that lies at the same locus on the homologous chromosome.
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Q2
Suggest the breeding method most suitable for animals that are below average in milk productivity.
Marks:1View AnswerAnswer:
Out-crossing is the best breeding method for animals that are below average in productivity in milk production.
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Q3
Suggest a technique to a researcher who needs to separate fragments of DNA.
Marks:1View AnswerAnswer:
Gel electrophoresis is a technique that can be used to separate DNA fragments of different sizes.
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Q4
Excessive nutrients in a fresh water body cause fish mortality. Give two reasons.
Marks:1View AnswerAnswer:
Excessive nutrients in a fresh water body cause fish mortality as:
- The release of nutrient-rich sewage and industrial effluents leads to growth of algae which results in deprivation of dissolved oxygen that is necessary for aquatic life.
- Other pollutants flowing into a lake may poison whole populations of fish, whose decomposing remains further deplete the water’s dissolved oxygen content.
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Q5
Give an example of a codon having dual function.
Marks:1View AnswerAnswer:
Codon AUG performs dual function.
It codes for methionine (Met) and also acts as an initiator codon.
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Q6
Discuss the role the enzyme DNA ligase plays during DNA replication.
Marks:2View AnswerAnswer:
During replication, the synthesis of one new strand of DNA on the DNA template with polarity 3’ to 5’is continuous. However, the synthesis of other new strand of DNA on the DNA template with polarity 5’ to 3’ is discontinuous i.e., in the form of small DNA fragments. These discontinuous DNA segments are called okazaki fragments. These fragments are later joined by the enzyme DNA ligase to form continuous strand called lagging strand.
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Q7
Distinguish between the roles of flocks and anaerobic sludge digesters in sewage treatments.
Marks:2View AnswerAnswer:
Flocs
Anaerobic Sludge Digester
Flocs are the masses of aerobic bacteria along with fungal filaments that grow in aeration tank during secondary treatment of effluent and consume a major part of the organic matter of the effluent. This reduces BOD of waste water.
In anaerobic sludge digester, anaerobic bacteria grow and digest the bacteria and fungi in the sludge and produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide (biogas)
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Q8
Name the causative organism of the disease amoebiasis. List three symptoms of the disease.
OR
Identify ‘A’, ‘B’, ‘C’ and ‘D’ in the given table.
Crop
Variety
Resistance to disease
A
Himgiri
Leaf rust
Cauliflower
Pusa Shubhra
B
Brassica
Pusa Swarnim
C
Cowpea
D
Bacterial blight
Marks:2View AnswerAnswer:
The causative organism of amoebiasis is Entamoeba histolytica.
The symptoms of amoebiasis are:
i. Constipation
ii. Abdominal pain and cramps
iii. Stool with excessive mucous and blood clots
OR
Crop
Variety
Resistance to disease
Wheat
Himgiri
Leaf rust
Cauliflower
Pusa Shubhra
Black rot and curl blight black rot
Brassica
Pusa Swarnim
White rust
Cowpea
Pusa komal
Bacterial blight
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Q9
Plants that inhabit a rainforest are not found in a wetland. Explain.
Marks:2View AnswerAnswer:
Plants found in rainforest are not found in wetlands as the climatic conditions are different in rainforest and wetland.
The climate of rainforest is wet and humid, so in this climate, large trees and shrubs are predominantly present.
The climate of wetlands is relatively cool and wet. Herbs and aquatic plants are predominantly present in wetlands.
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Q10
Angiosperms bearing unisexual flowers are said to be either monoecious or dioecious. Explain with the help of one example each.
Marks:2View AnswerAnswer:
Flowers that posses either stamens (male reproductive organs) or carpel (female reproductive organ) are called unisexual flowers.
The plant possessing both male and female flowers is called monoecious plant and the plant possessing either male or female flower is known as dioecious plant.
Example of monoecious plant is cucurbits and that of dioecious plant is papaya.
