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Why is DNA considered chemically less reactive and structurally more stable compared to RNA?
The text clearly states: 'Further, 2'-OH group present at every nucleotide in RNA is a reactive group and makes RNA labile and easily degradable. ... Therefore, DNA chemically is less reactive and structurally more stable when compared to RNA.'
Nucleic acids are polymers of nucleotides. A nucleotide is composed of:
The chemistry context states: 'Nucleic acids are the polymers of nucleotides which in turn consist of a base, a pentose sugar and phosphate moiety.'
Which of the following hormones is NOT produced in women only during pregnancy?
The NCERT text states, 'hCG, hPL and relaxin are produced in women only during pregnancy.' It also mentions that 'estrogens, progestogens, cortisol, prolactin, thyroxine, etc., are increased several-folds in the maternal blood' during pregnancy, implying progestogens are present even when not pregnant, albeit at lower levels.
During which month of pregnancy is the embryo's heart formed?
According to the NCERT text, 'In human beings, after one month of pregnancy, the embryo’s heart is formed. The first sign of growing foetus may be noticed by listening to the heart sound carefully through the stethoscope.'
The inner cell mass of the blastocyst differentiates into the embryo, while the outer layer, the trophoblast, develops finger-like projections after implantation. What are these projections called?
The NCERT states, 'After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood.'
What is the primary function of the umbilical cord in embryonic development?
The NCERT text specifies, 'The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo.' This implies both supply of nutrients/oxygen and removal of waste.
Which of the following is NOT a function of the placenta?
The NCERT states that the placenta 'facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials'. It also 'acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc.'. Oxytocin release is triggered by the foetal ejection reflex and comes from the maternal pituitary, not the placenta.
What is the correct sequence of events initiated by signals from the fully developed foetus and placenta leading to parturition?
The NCERT text says, 'The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscles and causes stronger uterine contractions.'
By the end of the second trimester (about 24 weeks) of pregnancy, which of the following developmental milestones are typically observed in the foetus?
The NCERT states, 'By the end of about 24 weeks (end of second trimester), the body is covered with fine hair, eye-lids separate, and eyelashes are formed.' Other options correspond to different stages.
The process of embedding the blastocyst in the endometrium of the uterus is called:
The NCERT states, 'As a result, the blastocyst becomes embedded in the endometrium of the uterus (Figure 2.11 step H). This is called implantation and it leads to pregnancy.'
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.