Question

The partner responsible for the sex of the child is
A. Male
B. Female
C. Both
D. At times male and at times female

Answer 1

Hint: When X chromosome of mothers pairs with Y Chromosome of father it leads to son and when the X chromosome of mother pairs with X chromosome of father it leads to a daughter. This type of sex determination is known as XX-XY type sex determination. It is also observed in Drosophila.

Complete answer: In XX-XY type of sex determination, the sex of the child is dependent on the father. Humans have sex chromosomes referred to as X and Y chromosomes. Gametes; egg and sperm are produced by meiosis and each gamete gets half the number of chromosomes of the parent cell. Mother has only X chromosome but the father has both X and Y chromosomes. When the X chromosome of a mother combines with the X chromosome of the father, it leads to the birth of a daughter and when the X chromosome of mother combines with Y chromosome of the father, it leads to the birth of a son. Hence, the sex of the baby is dependent on the father. There are 50% chances of girls and 50% chances of boys. Other types of sex determination are XX-XO type mostly present in insects. In this type, males have only one sex chromosomes X and females have two X chromosomes. Males are depicted by XO chromosomes and females are depicted by XX chromosomes. ZW-ZZ type is present in birds and reptiles. In this type, females are heterogametic and have two sex chromosomes Z and W and males are homogametic having two Z sex chromosomes. ZO-ZZ type is present in butterflies and moths. In this type, males have two Z sex chromosomes and females have only one Z sex chromosome.
Hence, the correct answer is option A.

Note: Some species such as various plants and fish do not have fixed sex, and instead go through life cycles and change sex based on genetic cues during corresponding life stages of their type. This could be due to environmental factors such as seasons and temperature.