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A disorder causing fatigue, weakening, and paralysis of skeletal muscle due to an autoimmune attack on the neuromuscular junction is:
The NCERT text defines Myasthenia gravis as an 'Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.'
Which of the following is an age-related disorder impacting bone structure and increasing fracture risk?
The NCERT text states: 'Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of fractures.'
Which of the following describes the functional male gametes and their role in fertilization in flowering plants?
The process of double fertilization involves two main fusions. One male gamete fuses with the egg cell to form the zygote, and the other male gamete fuses with the two polar nuclei in the central cell to form the Primary Endosperm Nucleus (PEN), which develops into the endosperm. This is a characteristic feature of angiosperm fertilization.
What is the ploidy level of the Primary Endosperm Nucleus (PEN) formed during double fertilization?
The Primary Endosperm Nucleus (PEN) is formed by the fusion of one male gamete (haploid, n) with the two polar nuclei (each haploid, n) present in the central cell. Therefore, the resulting PEN is triploid (n + n + n = 3n).
The fusion of one male gamete with the egg cell during double fertilization results in the formation of:
According to the process of double fertilization, one of the two male gametes released by the pollen tube fuses with the egg cell. This fusion is called syngamy or generative fertilization and leads to the formation of the diploid zygote.
Which of the following structures guides the entry of the pollen tube into one of the synergids?
The NCERT text states: 'The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid.'
Where does the 'triple fusion' specifically take place within the embryo sac?
Triple fusion is the fusion of one male gamete with the two polar nuclei. The polar nuclei are located in the large central cell of the embryo sac. Therefore, triple fusion occurs in the central cell.
A typical angiosperm embryo sac at maturity is described as 8-nucleate but 7-celled. Which nuclei are involved in forming the 7th cell and what is its role in double fertilization?
The NCERT text states: 'the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.' This large central cell, containing the two polar nuclei, fuses with one male gamete during triple fusion to form the primary endosperm nucleus, which later develops into the endosperm.
Which of the following sequences correctly traces the path of a pollen tube from the stigma to the ovule during fertilization?
The pollen grain germinates on the stigma, and the pollen tube grows through the tissues of the style and reaches the ovary. From the ovary, it enters the ovule through the micropyle, and then specifically enters one of the synergids. (Ref: 'Pollen tube grows through the tissues of the stigma and style and reaches the ovary... Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus').
Double fertilization is a unique characteristic feature of:
The chapter is titled 'Sexual Reproduction in Flowering Plants' (Angiosperms) and discusses double fertilization as a key event in their reproductive cycle. Double fertilization involving the formation of both a zygote and primary endosperm nucleus is exclusive to angiosperms.
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.