The chemical compounds produced by the host plants to protect themselves against fungal infection is 
Phytoalexins are non-specific antibiotic substances produced by plants in response to infection by a fungus.
White rust disease is caused by 
Albugo candida is an obligate parasite causing white rust on members of family Cruciferae and other hosts.
Azotobacter and Bacillus polymyxa are the examples of 
Azotobacter and Bacillus polymyxa are the examples of non-symbiotic nitrogenfixers.
Sex factor in bacteria is 
Sex-factor or F-factor in bacteria results in high frequency conjugation. It allows bacteria to produce sex pilus necessary for conjugation.
Influenza virus has 
Influenza virus is a retrovirus wherein, the genetic material comprises of RNA.
There are three genera of influenza virus, identified by antigenic differences in their nucleoprotein and matrix protein:
In bacterial chromosomes, the nucleic acid polymers are 
Bacterial chromosomes comprise of circular DNA.
Interferons are 
Interferons are virus induced proteins produced by cells infected with viruses. They are antiviral in action.
Which one of the following is not true about lichens? 
Lichens are composite dual organisms formed by the association between a fungus and a photosynthetic symbiont. The bulk of lichen body is formed of fungus.
Mycorrhiza is 
Association of algae and fungi is referred to as lichen. Symbiotic association of Rhizobium with roots of leguminous plants is referred to as symbiosis. Mycorrhiza is symbiotic association between fungi and roots of higher plants. The fungal partner of mycorrhiza obtains food from roots of the higher plant and in return supplies mineral elements to it.
The hereditary material present in the bacterium Escherichia coli is [1997, 98]
In any kind of Bacteria (E.coli) double stranded DNA is present.
The plasmids pesent in the bacterial cells are 
Plasmids are the extrachromosomal DNA.
Which one of the following statements about viruses is correct? 
Viruses have either DNA or RNA as the genetic material. Viruses having RNA as the genetic material are known as Retroviruses.
Most of the Lichens consist of 
The lichen fungus is typically a member of the Ascomycota rarely a member of the Basidiomycota. The algal or cyanobacterial cells are photosynthetic, and as in higher plants they reduce atmospheric carbon dioxide into organic carbon sugars to feed both symbionts. Both partners gain water and mineral nutrients mainly from the atmosphere through rain and dust. The fungal partner protects the alga by retaining water, serving as a larger capture area for mineral nutrients and, in some cases, provides minerals obtained from the substratum. If a cyanobacterium is present, as a primary partner or another symbiont in addition to green alga as in certain tripartite lichens, they can fix atmospheric nitrogen, complementing the activities of the green alga.
Two bacteria found to be very useful in genetic engineering experiments are 
Escherichia and Agrobacterium are both used as vectors in genetic engineering. Nitrobactor converts nitrites to nitrates. Azotobacter is a free living nitrogen fixing bacteria. Nitrosomonas converts ammonia to nitrite. Rhizobium is a symbiotic nitrogen fixing bacteria living in the root nodules of leguminous plants Diplococcus pneumoniae causes pneumonia.
The main role of bacteria in the carbon cycle involves 
Bacteria acts as decomposers in the carbon cycle.
A few organisms are known to grow and multiply at temperatures of 100–105ºC. They belong to 
These are archaebacteria which can tolerate high temperature.
Transfer of genetic information from one bacterium to another in the transduction process is through 
Transfer of genetic information from one bacterium to another by physical contact is called conjugation while if it takes place by some other medium like virus than it is called transduction.
Puccinia forms 
Puccinia causes black rust of wheat . It completes its life cycle in two hostswheat and barberry. Two types of spores are produced on wheat - uredospores and teleutospores.
Which one of the following micro-organisms is used for production of citric acid in industries?
Aspergillus niger is known as guinea pig of kingdom fungi. The main source of commercial preparation of citric acid is the fermentation of sugar with Aspergillus niger.
Yeast Saccharomyces cerevisiae is used in the industrial production of 
Yeast performs alcoholic fermentation because of enzyme ‘Zymase’. It is used in the production of ethyl alcohol or ethanol.
Due to which of the following organisms, yield of rice has been increased ? 
Azolla is a freshwater fern harbouring a bluegreen alga - Anabaena in its leaf cavities. The alga fixes atmospheric nitrogen and releases nitrogenous compounds in leaf cavities. This symbiotic system is the main source of algal biofertilizer in rice fields. When rice paddies are flooded in the spring, they can be inoculated with Azolla, which then quickly multiplies to cover the water, suppressing weeds. As the plants die, they contribute nitrogen to the rice plants, and as the rice paddy dries out, the Azolla all eventually die, making an exceptional green manure.
Photosynthetic bacteria have pigments in 
Chloroplasts, chromoplasts and leucoplasts are the types of plastids found in higher plants. Chloroplasts contain the green pigment chlorophyll. Chromoplasts contain coloured pigments. Leucoplasts are colourless and store starch granules.
In prokaryotes, the genetic material is 
In prokayotes nucleoid consist of double stranded circular DNA without histone protein.
A good green manure in rice fields is 
Aspergillus is a fungus, Mucor is also a fungus. Azolla harbours blue-green algae Anabaena which fixes N2, increasing fertility.
Enzymes are absent in 
Enzymes are absent in viruses because they are unable to transmit their nucleic acid from one host cell to another.