Question

A woman has only daughters. Analyse the situation genetically and provide a suitable explanation

Answer 1

Hint: The growth of sexual differences begins with the XY sex-determination system that is available in humans. Composite mechanisms are responsible for the progress of the phenotypic differences between male and female humans from an undifferentiated zygote. Females normally have two X chromosomes, and males characteristically have a Y chromosome and an X chromosome.

Complete answer:
Women contain two X chromosomes where men contain one X and one Y chromosome. Therefore, a female produces gametes that are all of the identical kind and only add in one chromosome to the zygote. The other chromosome arrives from the male and it can be either an X or Y chromosome.

- Possibility 1: If an X chromosome comes from the male then the zygote will possess XX condition and the resulting offspring will be a female (daughter).

- Possibility 2: If a Y chromosome comes from the male then the zygote will have XY condition and the consequent offspring will be a male (son).

Therefore, the woman has only daughters because only the sperms having the X chromosome fertilized the ovum each time.

Note: A human fetus does not grow its external sexual organs until seven weeks after fertilization. The fetus appears to be sexually identical, looking neither like a male or a female. Over the next five weeks, the fetus begins creating hormones that cause its sex organs to rise into either male or female organs. This process is known as sexual differentiation. The forerunner of the internal female sex organs is known as the Müllerian system.