OBJECTIVE QUESTIONS FOR NEET AIIMS JIPMER www wisedane
OBJECTIVE QUESTIONS FOR NEET AIIMS JIPMER www. wisedane. com
BIOLOGY HUMAN REPRODUCTION SET 1 MCQ’s www. wisedane. com
Q 1. Cells become variable in morphology and function in different regions of the embryo. The process is A. Differentiation B. Metamorphosis C. Organisation D. Rearrangement www. wisedane. com
ANSWER (A) EXPLANATION Ø Differentiation are the changes from simple to more complex forms undergone by developing tissues and organs so that they become specialized for particular functions. Ø Differentiation occurs during embryonic development and regeneration. www. wisedane. com
Q 2. Human eggs are A. Alecithal B. Microlecithal C. Mesolecithal D. Macrolecithal www. wisedane. com
ANSWER (A) EXPLANATION: Ø Eggs are of 4 types regarding the amount of yolk present in them: (i) Alecithal egg: Almost free of yolk e. g. man. (ii) Microlecithal egg: Very small amount of yolk e. g. (iii) Mesolecithal egg: Moderate amount of yolk eg. Frog’s egg (iv) Macrolecithal egg: Large amount of yolk Branchiostoma. eg, reptiles, birds and egg-. laying mammals www. wisedane. com
Q 3. Egg is liberated from ovary in A. Secondary oocyte stage B. Primary oocyte stage C. Oogonial stage D. Mature ovum stage. www. wisedane. com
ANSWER (A) EXPLANATION Ø In humans, ovum is released from the ovary in the secondary oocyte stage. The wall of the ovary gets ruptured to release the oocyte. Ø In human’s ovulation occurs about 14 days before the onset of the next menstruation. Ovulation is induced by LH. www. wisedane. com
Q 4. Gonads develop from embryonic A. Ectoderm B. Endoderm C. Mesoderm D. Both mesoderm and endoderm. www. wisedane. com
ANSWER (C) EXPLANATION: Ø Ectoderm, mesoderm and endoderm are three germ layers that give rise to specific tissues, organs and organ systems. Ø Gonads, muscles, dermis, kidneys etc. develop from mesoderm. Ectoderm produces epidermis, glands, nervous system etc. Pancreas, lining of urinary bladder etc develop from endoderm. www. wisedane. com
Q 5. How many sperms are formed from a secondary spermatocyte? A. 4 B. 8 C. 2 D. 6 www. wisedane. com
ANSWER (C) EXPLANATION Ø At sexual maturity, the undifferentiated primordial germ cells divide several times by mitosis to produce a large number of spermatogonia. Each spermatogonium actively grows to a larger primary spermatocyte. Each primary spermatocyte undergoes two successive divisions, called maturation divisions. Ø The first maturation division is reductional or meiotic. Hence, the primary spermatocyte divides into two haploid daughter cells called secondary spermatocytes. Both secondary spermatocytes now undergo second www. wisedane. com
Ø Thus each secondary spermatocyte gives rise to two spermatids that undergo transformation to form two sperms. Overall, both secondary spermatocytes give rise to four sperms. www. wisedane. com
Q 6. Fertilizins are emitted by A. Immature eggs B. Mature eggs C. Sperms D. Polar bodies. www. wisedane. com
ANSWER (B) EXPLANATION: Ø Mature egg (ovum) secretes a chemical named fertilizin (composed of glycoprotein = monosaccharides + amino acids). Ø Sperm has on its surface a protein substance called antifertilizin (composed of acidic amino acids). Ø The fertilizin of an egg interacts with the anti-fertilizin of a sperm of the same species. This interaction makes the sperms stick to the egg surface. www. wisedane. com
Q 7. During cleavage, what is true about cells? A. Nucleocytoplasmic ratio remains unchanged B. Size does not increase C. There is less consumption of oxygen D. The division is like meiosis. www. wisedane. com
ANSWER (B) EXPLANATION: Ø The term cleavage refers to a series of rapid mitotic divisions of the zygote following fertilization, forming a many-celled blastula. Ø Interphase in cleavage divisions is short and does not involve growth so that the resulting blastomeres become smaller in size as their number increases. Ø Thus, the size of the cells (blastomeres) does not increase during cleavage. www. wisedane. com
Q 8. Freshly released human egg has A. one Y-chromosome B. one X-chromosome C. two X-chromosome D. one X-chromosome and one Ychromosome www. wisedane. com
ANSWER (B) EXPLANATION: Ø The egg released is haploid (has only one X-chromosome and 22 autosomes) as it is formed due to meiotic division of diploid primary oocyte having XX chromosome and 44 autosomes. www. wisedane. com
Q 9. Location and secretion of Leydig’s cells are A. Liver-cholesterol B. Ovary-oestrogen C. Testis-testosterone D. Pancreas-glucagon. www. wisedane. com
ANSWER (C) EXPLANATION: Ø In between the seminiferous tubules in the connective tissue of testis, there are present small groups of rounded interstitial or Leydig’s cells which secrete androgens (e. g. , testosterone), i. e. male sex hormones. www. wisedane. com
Q 10. Middle piece of mammalian sperm possesses A. mitochondria and centriole B. mitochondria only C. centriole only D. nucleus and mitochondria. www. wisedane. com
ANSWER (A) EXPLANATION: Ø The middle piece of human sperm contains the mitochondria coiled around the axial filament called mitochondrial spiral. Ø They provide energy for the movement of the sperm. At the end of the middle piece there is a ring centriole (annulus) with unknown functions. www. wisedane. com
Q 11. Meroblastic cleavage is a division which is A. Horizontal B. Partial/parietal C. Total D. Spiral. www. wisedane. com
ANSWER (B) EXPLANATION Ø Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total or entire cleavage) or meroblastic (partial cleavage). Ø In the presence of a large amount of yolk in the fertilized egg cell, the cell can undergo partial or meroblastic cleavage. Ø Two major types of meroblastic cleavages are discoidal e. g. birds and superficial e. g. arthropods. www. wisedane. com
Q 12. Eye lens is formed from A. Ectoderm B. Mesoderm C. Endoderm D. Ectoderm and mesoderm. www. wisedane. com
ANSWER (A) EXPLANATION Ø Ectoderm, mesoderm and endoderm are three germ layers that give rise to the specific tissues, organs and organ-systems. Ø Ectoderm gives rise to conjunctiva, cornea, lens of eye, muscles of iris, vitreous humour, retina, lacrimal gland along with other parts of the body.
Q 13. Blastopore is A. Opening of neural tube B. Opening of gastrocoel C. Future anterior end of embryo D. Found in blastula. www. wisedane. com
ANSWER (B) EXPLANATION Ø Blastopore is the opening by which the cavity of the gastrula (gastrocoel), communicates with the exterior. It is formed as a result of invagination of endoderm during embryonic development. Ø During maturation of some animals it evolves into the anus or the mouth; in others it is covered over and contributes to the canal joining the primitive gut with the cavity of the neural tube. www. wisedane. com
Q 14. Extrusion of second polar body from egg nucleus occurs A. After entry of sperm before completion of fertilization B. After completion of fertilization C. Before entry of sperm D. Without any relation of sperm entry. www. wisedane. com
ANSWER (A) EXPLANATION Ø The entry of sperm stimulates the secondary oocyte to resume and complete the suspended meiosis II. This produces a haploid mature ovum and a second polar body. Ø The second polar body immediately degenerates www. wisedane. com
Q 15. In telolecithal egg the yolk is found A. All over the egg B. On one side C. Both the sides D. Centre. www. wisedane. com
ANSWER (B) EXPLANATION Ø Eggs with abundant yolk concentrated in one hemisphere of the egg are termed telolecithal. Ø This occurs in many invertebrates and in all vertebrates lower than marsupial mammals. www. wisedane. com
Q 16. Acrosome reaction in sperm is triggered by A. Capacitation B. Release of lysin C. Influx of na+ D. Release of fertilizin. www. wisedane. com
ANSWER (C) EXPLANATION: Ø The activated spermatozoan on reaching the egg plasma membrane undergoes a number of changes in its acrosomal region. All these changes are collectively described under acrosome reaction. Ø Acrosome reaction is calcium-dependent involving massive uptake of calcium and sodium with an efflux of hydrogen generating high p. H and osmotic pressure, producing negative surface charge, and partial or total release of the acrosomal enzymes. www. wisedane. com Ø Calcium influx may activate phospholipase resulting in
Q 17. Amount of yolk and its distribution are changed in the egg. Which one is affected? A. Pattern of cleavage B. Formation of zygote C. Number of blastomeres D. Fertilization. www. wisedane. com
ANSWER (A) EXPLANATION: Ø Based on the amount and pattern of distribution of yolk in the zygote, cleavage is of two types: holoblastic and mesoblastic. Ø Holoblastic cleavage divides the zygote and blastomeres completely into daughter cells. Ø In mesoblastic cleavage the divisions are confined to the animal pole or peripheral region of egg. The yolk remains undivided. www. wisedane. com
Q 18. Male hormone is produced in the testis by cells of A. Sertoli B. epithelial C. spermatocytes D. leydig. www. wisedane. com
ANSWER (D) EXPLANATION: Ø In between the seminiferous tubules in the connective tissue of testis, there are present small groups of rounded interstitial or Leydig’s cells which secrete androgens (e. g. , testosterone), i. e. male sex hormones. www. wisedane. com
Q 19. What is true about cleavage in the fertilized egg in humans? A. It starts while the egg is in fallopian tube B. It starts when the egg reaches uterus C. It is meroblastic D. It is identical to the normal mitosis. www. wisedane. com
ANSWER (A) EXPLANATION Ø Cleavage is a series of rapid mitotic divisions of the zygote which convert the single celled zygote into a multicellular structure called blastula (blastocyst). Ø About thirty hours after fertilization, the newly formed zygote divides into two cells, the blastomeres, in the upper portion of the Fallopian tube. This is the first cleavage. Ø The next division occurs within forty hours after fertilization. The third division occurs about three days after fertilization. Ø During these early cleavages, the young embryo is slowly moving down the fallopian tube towards the uterus. At the end of fourth day, the embryo reaches the uterus. It has thirty-two cells. www. wisedane. com
Q 20. In oogamy, fertilization involves A. A small non-motile female gamete and a large motile male gamete B. A large non-motile female gamete and a small motile male gamete C. A large non-motile female gamete and a small non-motile male gamete D. A large motile female gamete and a small non- motile malewww. wisedane. com
ANSWER (B) EXPLANATION Ø Oogamy is the sexual reproduction involving the formation and subsequent fusion of a large, usually stationary, female gamete and a small motile male gamete. Ø The female gamete may contain nourishment for the development of the embryo, which is often retained and protected by the parent organism. www. wisedane. com
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