Test: Sex Determination - NEET MCQ

The foundation of the chromosomal basis of sex determination was laid down by Henking in 1891. He studied a specific nuclear structure though spermatogenesis in a few insects.

Birds do not show male heterogametic conditions. Instead, they show the female heterogametic condition. Male heterogametic condition is characterised by male individuals producing two different types of gametes.

When the condition of male heterogamety is present, then sperm determines the sex of the offspring because two kinds of sperms are present, one with X-chromosome and the other with Y-chromosome. Eggs of an individual are the same as both of them contain 22+ X chromosomes.

Grasshoppers do not show XY type of male heterogametic condition. XY type of male heterogametic condition is shown by a number of insects like Drosophila and mammals including human beings and elephants, the males in this type bear two types of sex chromosomes- X and Y type.

The probability of having a girl child in the sixth pregnancy, where the first five progenies were male is 50%. As humans show XY type of male heterogamety, where 50% sperms carry 22+ X chromosomes and the other 50% carry 22+Y chromosomes, therefore in each pregnancy there is 50% probability of either a male or a female child.

• Honey bees exhibit a haplodiploid type of sex-determination system.
• This type of system has special characteristic features like the males produce sperms by mitosis.
• The male individuals do not have a father and thus cannot have sons, but can have a grandfather and a grandson.

XX-XO method of sex determination: Found in grasshoppers (iii).
XX-XY method of sex determination: Found in humans and many animals where females are homogametic (iv).
Karyotype-45: Associated with Turner's syndrome (i).
ZW-ZZ method of sex determination: Found in birds where females are heterogametic (ii).

Drosophila, like humans, follows the XX-XY method of sex determination. Other options are incorrect; for example, in birds, females are ZW and males are ZZ. Henking discovered the X-chromosome and the term "X-body," not the Y-chromosome specifically.

Complete answer: Drosophila flies have chromosomes X and Y, and also autosomes. With exception of humans, Y-chromosomes will not confer masculinity, rather they compile the genes necessary for sperm production. Conversely, sex is defined as the ratio of X chromosomes to autosomes. Each cell ancestry in Drosophila takes a sexual decision all its own. One of the main approaches to illustrate this is by examining XX-XY mosaic flies, i.e. individual flies including a combination of XX and XY cells. Such mosaics reveal a mixture of male and female phenotypes, focusing on the genotype of each cell. The understanding of this variation here is that every Drosophila cell decides its sex independently. Three main genes are involved in the determination of sex in Drosophila. They're sex-lethal, sisterless, and deadpan. Deadpan is an autosomal gene that prevents sex-lethal, whereas the X chromosome is held by the sisterless and prevents the action of the deadpan.
So, the correct answer is an option (B).
Additional information:
Henking has uncovered the X-chromosomes. The work has been the result of a Leipzig research of the firebug testicle, and during that Henking realized that one chromosome did not engage in meiosis. Male grasshoppers are regarded as heterogametic because they create two distinct kinds of sperm cells: both with and without X chromosomes. Female grasshoppers seem to possess XX and grasshoppers will use XX- XO sex-determining system. The ZW sex-determination framework is a chromosome process that determines the sex of descendants in birds, or fish, and crustaceans, such as that of the gigantic river pomegranate, some insects, some invertebrates. In this, women with ZW chromosomes and men with ZZ chromosomes.
Note: Drosophila flies rely on biological evolution, which implies that mating needs male and female flies to produce children. Flies usually participate in courting or mating conduct, in which they copulate. The female then makes eggs, believing that she would eat enough already, and identify the correct medium to lay them.

The sex determination in honey bee is based on the number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female (queen or worker), and an unfertilised egg develops as a male (drone) by means of parthenogenesis. This means that the males have half the number of chromosomes than that of a female. The females are diploid having 32 chromosomes and males are haploid, i.e., having 16 chromosomes. This is called as haplodiploid sex-determination system and has special characteristic features such as the males produce sperms by mitosis.