NEET Biology Reproduction Genetics and Biotechnology MCQs Set 04

Answer: (b) Scutellum

Explanation:
1. The cotyledon of the grass embryo is the scutellum, situated towards one side of the embryonal axis.
2. Coleoptile and coleorhiza are protective sheaths around the plumule and radicle, and the epiblast is a rudimentary structure on the opposite side.

Teacher's Note:
1. In grass seeds the scutellum absorbs nutrients from the endosperm.
2. The epiblast is regarded as a vestigial second cotyledon.

Answer: (b) Four

Explanation:
1. Endosperm is retained in the mature seeds of wheat, maize, barley and castor, which are endospermic.
2. In pea, groundnut and sunflower the endosperm is consumed during development, so they are non-endospermic.
3. So four seeds retain the endosperm.

Teacher's Note:
1. Endosperm forms in every angiosperm seed, but may be used up before maturity.
2. Non-endospermic seeds store food in their cotyledons.

Answer: (b) Parthenogenesis

Explanation:
1. Development of an unfertilized egg cell into an embryo is parthenogenesis.
2. Apospory and apogamy involve other cells of the ovule or embryo sac, and parthenocarpy is fruit formation without fertilization.

Teacher's Note:
1. Parthenogenesis is common in bees, where drones develop from unfertilized eggs.
2. Parthenocarpy gives seedless fruits.

Answer: (d) Apomixis

Explanation:
1. Apomixis is the production of seeds without fertilization.
2. It is a form of asexual reproduction that mimics sexual reproduction.

Teacher's Note:
1. Amphimixis is the normal sexual process with fusion of gametes.
2. Apomixis in hybrids can fix hybrid vigour in the seed.

Answer: (c) 20

Explanation:
1. The aleurone layer is the outer layer of the endosperm and is triploid, so \(3n = 30\) and \(n = 10\).
2. The secondary nucleus is diploid (fusion of two polar nuclei), so it has \(2n = 20\) chromosomes.

Teacher's Note:
1. The secondary nucleus fuses with one male gamete to form the triploid endosperm.
2. Aleurone layer cells are 3n.

Answer: (d) Prostate gland

Explanation:
1. Seminal vesicles, bulbourethral (Cowper's) glands and Bartholin's glands occur in pairs.
2. The prostate is a single gland that surrounds the urethra at its base.

Teacher's Note:
1. Bartholin's glands are in the female and Cowper's glands in the male.
2. The prostate gland secretion makes up a large part of semen.

Answer: (d) All of the above

Explanation:
1. Seminiferous tubules open into the rete testis, which opens through the vasa efferentia (10-20 in number) into the epididymis.
2. Each vas deferens is a single duct from the epididymis, so all three statements are wrongly applied to the vas deferens.

Teacher's Note:
1. The sequence is seminiferous tubules, rete testis, vasa efferentia, epididymis, vas deferens.
2. There is only one vas deferens for each testis.

Answer: (a) Myometrium

Explanation:
1. The myometrium is the thick middle layer of smooth muscle of the uterus.
2. It shows strong contractions during delivery.

Teacher's Note:
1. The endometrium undergoes cyclic changes during the menstrual cycle.
2. The perimetrium is the thin outer layer.

Answer: (a) 15-20 mammary lobes

Explanation:
1. The glandular tissue of each breast is divided into 15-20 mammary lobes containing clusters of cells called alveoli.
2. So (a) is correct, while alveoli and tubules are not the first level of division.

Teacher's Note:
1. The alveoli secrete milk into the mammary tubules.
2. The tubules of each lobe join to form a mammary duct.

Answer: (d) Zero

Explanation:
1. Primary oocytes begin meiosis I during foetal life but arrest at prophase I.
2. The first polar body is formed only after puberty, just before ovulation, so none is formed before puberty.

Teacher's Note:
1. Meiosis I of the oocyte completes only just before ovulation.
2. Meiosis II is completed only if the sperm enters the secondary oocyte.

Answer: (c) Both (a) and (b)

Explanation:
1. Metamorphosis of the non-motile spermatid into the motile sperm is called spermiogenesis (also called spermateleosis).
2. Spermatogenesis is the entire process of sperm formation from the spermatogonia.

Teacher's Note:
1. Spermiation is the release of the sperm into the lumen of the seminiferous tubule.
2. Both terms (a) and (b) describe the same transformation.

Answer: (c) A, B and C

Explanation:
1. Primary oocytes are arrested in prophase I from foetal life.
2. After puberty, under the action of LH, meiosis I is completed just before ovulation, during the maturation phase, giving the secondary oocyte and the first polar body.
3. So statements A, B and C are correct, and D is wrong.

Teacher's Note:
1. Meiosis I of oogenesis is completed only after puberty.
2. The arrest at prophase I lasts for years.

Answer: (a) The secretory nature of the uterus is developed by progesterone produced by the corpus luteum

Explanation:
1. After ovulation the corpus luteum secretes progesterone, which makes the endometrium secretory.
2. Menstruation is caused by the fall in progesterone, not by its secretion, so (b) is wrong.
3. Injected estrogen and progesterone inhibit FSH and LH, so follicle growth is not increased (c is wrong), and estradiol rises before ovulation (d is wrong).

Teacher's Note:
1. Progesterone maintains the endometrium for implantation.
2. A sudden drop in progesterone and estrogen triggers menstruation.

Answer: (d) Estrogen

Explanation:
1. Estrogen peaks once just before ovulation from the growing follicles.
2. It peaks again in the luteal phase because the corpus luteum secretes estrogen along with progesterone.

Teacher's Note:
1. LH has a single mid-cycle surge.
2. Progesterone has a single peak in the luteal phase.

Answer: (d) Cows

Explanation:
1. Menstrual cycle occurs in primates such as humans, apes and old world monkeys.
2. Non-primate mammals such as cows show an oestrous cycle, with no menstrual bleeding.

Teacher's Note:
1. In an oestrous cycle the endometrium is reabsorbed instead of being shed.
2. Females are receptive to mating only during oestrus.

Answer: (a) Trophoblast

Explanation:
1. The blastocyst has an outer trophoblast layer and an inner cell mass.
2. The trophoblast cells in contact with the endometrium attach to it, and the inner cell mass later forms the embryo.

Teacher's Note:
1. The trophoblast later forms the chorion of the placenta.
2. Implantation happens about 7 days after fertilization.

Answer: (b) Embryo with 8 to 16 blastomeres

Explanation:
1. The zygote divides by cleavage into 2, 4 and 8 blastomeres, and the embryo with 8 to 16 blastomeres is called the morula.
2. The morula then forms the blastocyst.

Teacher's Note:
1. A morula is a solid ball of cells.
2. The blastocyst has a cavity filled with fluid.

Answer: (a) Four

Explanation:
1. The corpus luteum secretes progesterone, estrogen, relaxin and inhibin.
2. FSH, LH and PRL come from the pituitary, oxytocin from the posterior pituitary and zona lysin from the sperm acrosome.

Teacher's Note:
1. Progesterone is the main hormone of the corpus luteum.
2. Androgens are secreted by the theca cells and the testis.

Answer: (a) Oxytocin from maternal pituitary

Explanation:
1. The foetal ejection reflex triggers release of oxytocin from the maternal posterior pituitary.
2. Oxytocin acts on the uterine muscle and stimulates stronger contractions in a positive feedback loop.

Teacher's Note:
1. Parturition is a neuroendocrine mechanism.
2. Oxytocin also stimulates milk ejection after birth.

Answer: (c) Secondary oocyte

Explanation:
1. At ovulation the Graafian follicle ruptures and releases the secondary oocyte (arrested at metaphase II).
2. The primary oocyte completes meiosis I before ovulation and becomes the secondary oocyte.

Teacher's Note:
1. The secondary oocyte completes meiosis II only after sperm entry.
2. Oogonia are present only in foetal life.

Answer: (d) A-a, B-c, C-b, D-d

Explanation:
1. Hysterectomy is the surgical removal of the uterus (A-a).
2. Tubectomy is cutting and ligating the fallopian tubes (B-c).
3. Oophorectomy is removal of the ovaries (C-b) and vasectomy is cutting and tying of the vas deferens (D-d).

Teacher's Note:
1. The suffix -ectomy means surgical removal.
2. Tubectomy and vasectomy are permanent methods of birth control.

Answer: (b) 1951

Explanation:
1. India was among the first countries to initiate family planning programmes at the national level.
2. The action plans were initiated in 1951 and are periodically assessed.

Teacher's Note:
1. The programme is now called the Reproductive and Child Health Care programme.
2. Amniocentesis for sex determination has been banned by law.

Answer: (a) blocks estrogen receptors in the uterus, preventing the zygote from getting implanted

Explanation:
1. Saheli is a non-steroidal oral pill containing centchroman.
2. It acts as a selective estrogen receptor modulator, blocking estrogen receptors in the uterus so that the zygote cannot implant.

Teacher's Note:
1. Saheli is taken once a week and has few side effects.
2. It was developed at the Central Drug Research Institute, Lucknow.

Answer: (a) Progestasert

Explanation:
1. Hormone releasing IUDs such as Progestasert and LNG-20 make the uterus unsuitable for implantation and the cervix hostile to sperms.
2. Multiload-375 and Lippes loop are non-medicated or copper releasing devices, which mainly increase phagocytosis of sperms.

Teacher's Note:
1. Cu releasing IUDs suppress sperm motility and the fertilising capacity of sperms.
2. Nirodh is a condom, a barrier method.

Answer: (a) First trimester

Explanation:
1. MTPs are considered relatively safe up to 12 weeks, the first trimester of pregnancy.
2. Second trimester abortions are much riskier and need great care.

Teacher's Note:
1. MTP was legalised in India in 1971 with strict conditions.
2. Third trimester abortions are not allowed except in special circumstances.

Answer: (b) IUT

Explanation:
1. In IVF, fertilization is done outside the body and the zygote or early embryo is transferred.
2. Embryos with up to 8 blastomeres are transferred into the fallopian tube (ZIFT), while embryos with more than 8 blastomeres are transferred into the uterus (IUT).
3. Of the options given, IUT is the technique used in the test tube baby programme.

Teacher's Note:
1. IVF followed by embryo transfer (ET) is the full name of the technique.
2. GIFT transfers gametes into the fallopian tube.

Answer: (b) Jaundice

Explanation:
1. Amniocentesis tests the fluid taken from around the foetus for the chromosomal pattern and for certain metabolic disorders.
2. It can show sex, Down syndrome and metabolic disorders, but not jaundice.

Teacher's Note:
1. Foetal cells in the amniotic fluid are used for karyotyping.
2. Its misuse for sex determination is banned.