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A reduction step during meiosis is important because:
Meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organisms whereas fertilisation restores the diploid phase. We come across meiosis during gametogenesis in plants and animals. This leads to the formation of haploid gametes.
(page-167)
Let a cell's generation time is 1 minute. In 20 minutes a culture tube (culture medium) is 1/8th filled with cells. When the tube will be fullfilled?
Generation time = 1 minute
Cells divide in 1 minute = 2^1 = 2
2 minutes = 2^2 = 4
20 minutes = 2^20 = 1/8 of tube filled with cells
Total volume tube can hold = 2^20 X 8
= 2^20 X 2^3
= 2^23
= 23 minutes
Identify the meiotic stage in which the homologous chromosomes separate while the sister chromatids remain associated at their centromeres:
In anaphase I, the homologous chromosomes separate, while sister chromatids remain associated at their centromeres.
(page-169)
When a plant is flooded it often increases its production of
When a plant is flooded it often increases its ethylene. Ethylene shuts down leaf growth very fast after the plant senses limited water availability
The plant hormone, _______________ , plays a role in closing of stomata.
During biological nitrogen fixation, inactivation of nitrogenase by oxygen poisoning is prevented by
During biological nitrogen fixation, inactivation of nitrogenase by oxygen poisioning is prevented by leghaemoglobin.
It is a red-pigment that is filled outside the peribacteroid space in the cytosol of nodule cells. It is similar to haemoglobin of red blood cells. It has the ability to combine very rapidly with oxygen and thus acts as a very efficient O2 scavenger.
An organism used as a biofertilizer for raising soyabean crop is
(b) Rhizobium leguminosarum is a symbiotic bacteria found in root nodules of legume. This bacterium has nitrogen fixing gene and fixing N2. Soyabean is a legume. Thus, Rhizobium is used as a biofertilizer for raising soyabean crop.
Leghaemoglobin is produced in response to
(d) : Bacteria like Rhizobium and Frankia live free as aerobes in the soil but are unable to fix nitrogen. They develop the ability to fix nitrogen only as a symbiont when they become anaerobic. They are unable to fix nitrogen by themselves. Roots of a legume secrete chemical attractants. Bacteria collect over the root hairs and form an infection thread enclosing the bacteria. Infection thread grows alongwith multiplication of bacteria. Bacteria stop dividing and form irregular polyhedral structures called bacteroids. In an infected cell bacteriods occur in groups surrounded by host membrane. The host cell develops a pinkish pigment called leghaemoglobin (Lb). It is oxygen scavenger and is related to blood pigment haemoglobin. It protects nitrogen fixing enzyme nitrogenase from oxygen.
For the synthesis of Auxin and activation of carboxylase, which of the following ion is involved?
Page number-198
12.2.2 Role of Macro and Micronutrients
Mineral Nutrition
In photorespiration, glycolate is converted into serine and carbon dioxide in:
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