Question

In bugs and cockroaches (insects), the sex determination takes place by
A. XX and XO chromosomes
B. XX and XY chromosomes
C. ZZ-ZW chromosomes
D. ZO-ZZ chromosomes

Answer 1

Hint:The female chromosome of these insects is the same as human. The male of these insects has only one sex chromosome.

Complete answer:
To answer this question, first, we need to know aboutsex chromosome and sex determination. Sex chromosome is a pair of chromosomes deciding whether an individual is male or female. Scientists mark the sex chromosomes of human beings and other animals as X and Y. The sex chromosomes in humans consist of one pair of 23 pairs of chromosomes. The other 22 chromosome pairs are termed autosomes.However, genes rather than chromosomes primarily act as the underlying basis for sex determination in many species.

Now lets us find the solution from the given options-
>Many insects like real bugs, grasshoppers, cock-roaches, the females have two sex chromosomes, XX, while the males only have one sex chromosome, X. There is no chromosome of second sex. The males are therefore marked as X0. The females are homogametic in that they only contain one type of eggs (A+X).
>XX-XY chromosome is found in humans and in other animals. In this system, the females have a pair of identical XX chromosomes while male have dissimilar XY chromosomes.
>The ZZ-ZW chromosome is found in birds, reptiles, and fish. In this system, the females have a pair of dissimilar ZW chromosomes while the males have two identical ZZ chromosomes.
>For some butterflies and moths,these ZO-ZZ chromosomes of sex determination exist. This is precisely the reverse of the condition found in grasshoppers and cockroaches. There the females have different sex chromosomes (AA+Z) while the males have two homomorphic sex chromosomes (AA+ZZ). The females are predominantly heterogametic.

Thus, the right answer is option A i.e., XX and XO chromosomes.

Note: The female is XX and is the homogametic sex in species such as bugs, cockroaches, and certain other insects. The male is heterogametic but has only one sex chromosome. For XX-XO systems, the male produces gametes with a sex chromosome (X) or without (O).