The correct option is (c) 1 and 3 only.
Explanation
Human sex determination follows the XX-XY mechanism. Humans have 23 pairs of chromosomes, of which 22 pairs are autosomes and one pair consists of sex chromosomes. Females are homogametic (XX), while males are heterogametic (XY).Statement-wise Analysis:
- Statement 1 is Correct: Males possess one X and one Y chromosome (XY). During spermatogenesis (formation of sperms), two types of gametes are produced in equal proportions: 50% of sperms carry the X chromosome, and the other 50% carry the Y chromosome.
- Statement 2 is Incorrect: Females possess two X chromosomes (XX). Consequently, all haploid gametes (ova or eggs) produced by a female contain only the X chromosome. An unfertilized egg cannot contain a Y chromosome.
- Statement 3 is Correct: The sex of the zygote is determined by the sperm that fertilizes the egg. If a sperm carrying the X chromosome fertilizes the egg (which always carries an X), the resulting zygote will have an XX genotype and develop into a female. Conversely, if a sperm carrying the Y chromosome fertilizes the egg, the zygote will be XY and develop into a male.
Key Takeaway: In humans, the sex of the child is determined by the type of sperm (X or Y) that fertilizes the ovum; therefore, the genetic makeup of the father determines the sex of the offspring.