T. O. Diener discovered a new infectious agent that was smaller than viruses and have the following characteristics.
(i) It causes potato spindle tuber disease.
(ii) It has free RNA.
(iii) Molecular weight of RNA is low.
Identify the infections agent.
Viruses
Viroids
Virion
Mycoplasma
Correct Answer :
B. Viroids
Viroids cause potato spindle tuber disease (PSTV), chrysanthemum stunt, citrus exocortis, cucumber pale fruit etc. They cause persistent infections, i.e., never recovered.
Related Questions
The given characters are seen in which of the following group?
(i) Unicellular, colonial, filamentous, marine or terrestrial forms.
(ii) The colonies are surrounded by a gelatinous sheath.
(iii) Some can fix atmospheric nitrogen in specialized cells called heterocysts.
(iv) They often form blooms in water bodies.
Archaebacteria
Cyanobacteria
Chrysophytes
Dinoflagellates
Which of the following statement is incorrect ?
TMV has a double-stranded RNA molecule.
Most plant viruses are RNA viruses.
The bacteriophage has a double-stranded DNA molecule.
Most animal viruses are DNA viruses.
In some viruses, RNA is present instead of DNA indicating that
their nucleic acid must combine with host DNA before replication.
they cannot replicate.
there is no hereditary information.
RNA can transfer heredity material.
Which of the following is a parasitic fungi on the mustard plant ?
Albugo
Puccinia
Yeast
Ustilago
How many bacteria are produced in four hours if a bacterium divides once in half an hour ?
8
64
16
256
T. O. Diener discovered a new infectious agent that was smaller than viruses and have the following characteristics.
(i) It causes potato spindle tuber disease.
(ii) It has free RNA.
(iii) Molecular weight of RNA is low.
Identify the infections agent.
Viruses
Viroids
Virion
Mycoplasma
Match the terms given in column-I with their examples given in column-II and choose the correct option
| Column-I | Column-II |
|---|---|
| (Terms) | (Examples) |
| A. Ascus | I. Spirulina |
| B. Basidium | II. Penicillium |
| C. Protista | III. Agaricus |
| D. Cyanobacteria | IV. Euglena |
| E. Animalia | V. Sponges |
A II, B III, C IV, D V, E I
A I, B II, C III, D V, E IV
A II, B V, C III, D I, E IV
A II, B III, C IV, D I, E V
Bacteria and yeast are similar in all the following features except that
both are unicellular.
both are prokaryotes.
both are capable of causing fermentation.
both produce spores.
Why food can be kept for a longer time in cold house than in normal conditions ? Because,
insect cannot enter.
bacterial multiplication stops.
bacterial multiplication is reduced.
there is plasmolysis at low temperature.
Read the following statements and answer the question given below
(i) They are saprophytic protists.
(ii) Under suitable conditions, they form an aggregation (called plasmodium) which may grow and spread over several feet.
(iii) During unfavourable conditions, the plasmodium differentiates and forms fruiting bodies bearing spores at their tips.
Which of the following class of protists is being described by the above statements ?
Euglenoids
Dinoflagellates
Slime moulds
Protozoans
Which of the following statement is/ are correct for bacteria ?
They are the members of the kingdom monera.
They live in extreme habitats such as hot springs, deserts, snow and deep oceans.
They show the most extensive metabolic diversity.
All of the above
Consider the following statements with respect to characteristic features of the kingdom.
(i) In animalia, the mode of nutrition is autotrophic.
(ii) In monera, the nuclear membrane is present.
(iii) In protista, the cell type is prokaryotic.
(iv) In plantae, the cell wall is present.
Of the above statements, which one is correct ?
(i) only
(ii) only
(iii) only
(iv) only
Which of the following groups of protozoan is not correctly matched with its feature?
Amoeboid - Marine forms have silica shells on their surface.
Flagellated - Either free living or parasitic.
Ciliated - Actively moving organisms due to presence of cilia.
Sporozoans - Move and capture their prey with the help of false feet.
The subunit of capsid is called
core
nucleotide
amino acid
capsomere
Bacteria lack alternation of generation because there is
neither syngamy nor reduction division.
no distinct chromosomes.
no conjugation.
no exchange of genetic material.
When a moist bread is kept exposed in air, it becomes mouldy and black because
spores are present in the water.
spores are present in the bread.
spores are present in the air.
the bread decomposes.
Which one of the following statement is correct for archaea?
Archaea resemble eukaryotes in all respects.
Archaea have some novel features that are absent in other prokaryotes and eukaryotes.
Archaea completely differ from both prokaryotes and eukaryotes.
Archaea completely differ from prokaryotes.
Protozons are not included in kingdom animalia because they are
mostly asymmetrical.
unicellular eukaryotes.
heterotrophic in nature.
multicellular prokaryotes.
Which of the following statement(s) is/are correct about class basidiomycetes ?
(i) They are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known.
(ii) They grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts.
(iii) The mycelium is branched and septate.
(iv) Some common members are Agaricus, Ustilago and Puccinia.
Only (i)
Both (ii) and (iii)
(ii), (iii) and (iv)
All of these
Match column I (Kingdom) with column II (Class) and select the correct options
| Column-I | Column-II |
|---|---|
| (Kingdom) | (Class) |
| A. Plantae | I. Archaebacteria |
| B. Fungi | II. Euglenoids |
| C. Protista | III. Phycomycetes |
| D. Monera | IV. Algae |
A IV, B III, C II, D I
A I, B II, C III, D IV
A III, B IV, C II, D I
A IV, B II, C III, D I
Which class of fungi lacks sex organs but the process of plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains or genotypes?
Sac fungi
Bracket fungi
Imperfect fungi
Phycomycetes
Which scientist classify plants into trees, shrubs and herbs & animals into two groups having red blood cells and without red blood cells?
Aristotle
R. H. Whittaker
D. J. Ivanowsky
W. M. Stanley
Plasmogamy is the fusion of
two haploid cells including their nuclei.
two haploid cells without nuclear fusion.
sperm and egg.
sperm and two polar nuclei.
Bladderwort and Venus fly trap are examples of
insectivorous plants
parasitic plants
N2 rich plants
aquatic plants
A virus can be considered a living organism because it
responds to touch stimulus
respires
reproduces (inside the host)
can cause disease
Which of the following is not a viral disease ?
AIDS and mumps
Small pox and herpes
Influenza
Cholera
Ustilago causes plant diseases (called smuts) because
they parasitize on cereals.
they lack mycelium.
they develop sooty masses of spores.
their affected parts becomes completely black.
Match the class of fungi given in column I with their examples given in column II and choose the correct option
| Column-I | Column-II |
|---|---|
| (Class of fungi) | (Examples) |
| A. Ascomycetes | I. Rhizopus |
| B. Basidiomycetes | II. Penicillium |
| C. Deuteromycetes | III. Ustilago |
| D. Phycomycetes | IV. Alternaria |
A IV, B III, C I, D II
A II, B III, C IV, D I
A IV, B I, C II, D III
A III, B IV, C II, D I
Match the class of fungi given in column-I with their common name given in column-II and select the correct option.
| Column-I | Column-II |
|---|---|
| (Class of fungi) | (Common name) |
| A. Phycomycetes | I. Sac fungi |
| B. Ascomycetes | II. Algal fungi |
| C. Basidiomycetes | III. Fungi imperfecti |
| D. Deuteromycetes | IV. Club fungi |
A II, B I, C IV, D III
A II, B IV, C I, D III
A IV, B I, C II, D III
A IV, B III, C II, D I
Mycorrhizae are useful for plants because they
fix atmospheric nitrogen.
enhance absorption of nutrients from the soil.
kill insects and pathogen.
provide resistance against abiotic stresses.