Sex determination Definition

In biology, sex determination refers to a system that determines the sexual characteristics of an organism or its offspring. It aids in determining whether the organism will be male or female, the two most common sexes. The most common method is chromosomal sex determination, in which the male’s sex chromosome, i.e. the X or Y chromosome, determines the offspring’s sex or gender. In most cases, females have XX chromosomes and males have XY chromosomes. Genetic tests can also be used to rule out any chromosomal or genetic abnormalities. The genetic process of determining an organism’s sex is known as sex determination. Let’s take a closer look at this.

Determination of Chromosomal Sex

Before we can understand how sex is determined, we must first understand a person’s genetic makeup. Humans have 46 chromosomes, which are divided into 23 pairs. There are 22 pairs of autosomes and one pair of sex chromosomes among these 23 pairs. This is the only pair that can help determine a person’s gender.

Hermann Henking, a German scientist, was the first to investigate this in 1891. In the insect he was studying, he first noticed a different nuclear material in some of the male gametes. The X chromosome was given that name. He also noticed that many insects only had one chromosome, which he labelled as XO. The studies on sex determination in both sexes in all animals began here.

Human Sex Determination

Human females have two X chromosomes, one of which is inherited from each parent and is designated as XX. Human males have one X and one Y chromosome, with the X originating from the mother and the Y originating from the father. In some ways, the father determines the gender of the unborn child. This can put a lot of history to shame, in which people thought the woman was to blame for the lack of a male heir. The absence of the Y chromosome also qualifies an individual as female.

During spermatogenesis, males produce both types of gametes, one with the X chromosome and the other with the Y. The sex of the resulting zygote will be determined by which gamete of the father will fuse with the X of the mother at the time of fertilisation. As a result, there is a 50% chance that the child will be male and a 50% chance that it will be female.

Various methods for determining sex

• The human XX-XY system, in which XX represents the female and XY represents the male. This characteristic is also shared by a few insects.
• The ZW-ZZ system is used in birds, with ZW representing the heteromorphic female and ZZ representing the homomorphic male. This is also seen in a few fish and insects.

The Environment and Sex Determination

As previously mentioned in the discussion of Talaeporia tubulosa, environmental factors can sometimes play an important role in sex determination. The temperature has a strong influence on sex determination in certain groups of reptiles among vertebrates, and insects are no exception. In crocodilian reptiles and most turtles, egg incubation temperature, for example, determines sex. This theme comes in a variety of variations. Females are produced when eggs are incubated at temperatures below 22°C or above 28°C in the alligator snapping turtle, Macroclemys temminckii, while males are produced when eggs are incubated at intermediate temperatures. The biphasic temperature dependence of American alligators is similar, but the curve is shifted to higher temperatures. In the European pond turtle, Trachemys scripta, incubation temperatures above 30°C result in all females, while temperatures below 25°C result in all males. At 28.5°C, males and females are produced in equal numbers.

The temperature-dependent component of the sex-determination pathway in the European turtle, Emys orbicularis, has been extensively studied. The temperature-dependent component in E. orbicularis appears to be the synthesis of the enzyme aromatase, which converts androgens like testosterone into estrogens. At higher temperatures, increased aromatase activity produces more estrogens, skewing the sex ratio toward more females.

When the various mechanisms for determining sex among species are compared, it is clear that evolution has produced a variety of solutions for producing different sexes. Sexual reproduction has tremendous adaptive value for a species because it introduces new genetic variability into a population with each new generation. Even though chromosomes play an important role in the development of most species, environmental factors add new wrinkles to the process.

CONCLUSION:

 It is important to note that prenatal sex determination is illegal in many countries, including India. Amniocentesis is a procedure that examines the amniotic fluid to see if the foetus has any abnormalities. This procedure also reveals the gender of the unborn child. Because of abortions of female foetuses in countries such as India, the government has made this sex determination process illegal. Sex determination is legal in many Western countries.