Question

Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environmental ones, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However in human beings, the sex of an individual is largely determined genetically.

1. In what way are the sex chromosomes 'X' and 'Y' different in size? Name the mismatched pair of sex chromosome in humans.
2. Write the number of pair/pairs of sex chromosomes present in human beings. In which one of the parent (male/female) perfect pair/pairs of sex chromosome are present?
3. Citing two examples, justify the statement "Sex of an individual is not always determined genetically".

OR

Draw a flow chart to show that sex is determined genetically in human beings. 

Answer 1

1. Male sex chromosomes are known as mismatched pairs because they have one X chromosome that is normal size and one Y chromosome that is small in size.
2. There is just one set of sex chromosomes in a human chromosome. The ideal sex chromosomal pair for women is named X on both of them.
3. The methods used by various animals to determine sex differ greatly. The temperature at which fertilised eggs are maintained impacts whether the creatures forming in the eggs will be male or female in some species, such as a few reptiles. Individuals in other creatures, like snails, may change their sex, proving that sex is not genetically set.

OR

Sex determination in human beings: