Sex Determination in Humans — NEET Biology
📚 Practice ConceptIt has already been mentioned that the sex determining mechanism in case of humans is XY type. Out of 23 pairs of chromosomes present, 22 pairs are exactly same in both males and females; these are the autosomes. A pair of X-chromosomes are present in the female, whereas the presence of an X and Y chromosome are determinant of the male characteristic. During spermatogenesis among males, two types of gametes are produced. 50 per cent of the total sperm produced carry the X-chromosome and the rest 50 per cent has Y-chromosome besides the autosomes. Females, however, produce only one type of ovum with an X-chromosome. There is an equal probability of fertilisation of the ovum with the sperm carrying either X or Y chromosome. In case the ovum fertilises with a sperm carrying X-chromosome the zygote develops into a female (XX) and the fertilisation of ovum with Y-chromosome carrying sperm results into a male offspring. Thus, it is evident that it is the genetic makeup of the sperm that determines the sex of the child. It is also evident that in each pregnancy there is always 50 per cent probability of either a male or a female child. It is unfortunate that in our society women are blamed for giving birth to female children and have been ostracised and ill-treated because of this false notion.
Which of the following statements regarding sex determination in humans is/are correct? S1: Human males are homogametic, producing only X-carrying sperms. S2: Females produce two types of ova, 50% carrying X chromosome and 50% carrying Y chromosome. S3: Fertilization of an ovum by a Y-chromosome carrying sperm results in a female offspring. S4: Autosomes are present in equal number in both males and females. S5: The sex of the child is genetically determined by the genetic makeup of the ovum.
View solution & NCERT explanation
Correct answer: A — Only S4 is correct
The core concept here is sex determination in humans, which is of the XY type, and the roles of male and female gametes. S1: Human males are heterogametic (XY), producing two types of sperms: 50% carrying X-chromosome and 50% carrying Y-chromosome. Thus, S1 is incorrect. S2: Females are homogametic (XX), producing only one type of ovum, which always carries an X-chromosome. Thus, S2 is incorrect. S3: Fertilization of an ovum (always X) by a Y-chromosome carrying sperm results in a male offspring (XY). Fertilization by an X-chromosome carrying sperm results in a female offspring (XX). Thus, S3 is incorrect. S4: In humans, out of 23 pairs of chromosomes, 22 pairs are autosomes and are exactly the same in both males and females. Thus, S4 is correct. S5: It is the genetic makeup of the sperm (carrying either X or Y) that determines the sex of the child, as the ovum always carries an X chromosome. Thus, S5 is incorrect. Therefore, only statement S4 is correct. The question tests the understanding of human sex determination, including gamete formation and the role of male vs. female in sex determination.
What does NCERT say about It has already been?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.