Sex Determination

Sex determination in humans is the process of ascertaining the biological sex, classified as either a male or a female, of an offspring. Sexual differentiation is essential for the survival of many plants and animals throughout their life cycles. Although a pair of sex chromosomes frequently plays a significant role in sexual maturation, genes on these chromosomes and autosomes provide the fundamental basis for sex determination. Therefore, genetics has a role in determining a person’s sexual orientation.

Determination of Sex

Sex determination is a biological process that determines an organism’s or offspring’s sexual traits. It helps to distinguish whether the organism is male or female. The most widely used procedure is chromosomal sex determination. The male sex chromosome, i.e. the X or Y chromosome, determines the offspring’s sex or gender.

Sex chromosomes are the chromosomes that determine a person’s sex. The X and Y chromosomes are the two types of sex chromosomes. In most situations, females carry the XX chromosome, whereas males have the XY chromosome. Genetic tests can also be used to rule out chromosomal or genetic abnormalities. The genetic method of identifying an organism’s sex is known as sex determination.

Sex Chromosomes

Counting and studying metaphase chromosomes from male and female dividing cells reveal the chromosomal mechanism of sex determination in humans. There are 46 chromosomes in the typical karyotype, with two of them being X chromosomes (46XX, female) or one X chromosome along with one Y chromosome (46XY, males). This appears to be similar to the condition in Drosophila melanogaster. It is where females have two autosomal chromosomes and two X chromosomes (2AXX), whereas males have two autosomal chromosomes and one X with one X Y chromosome (2AXY).

Sex Determination with Chromosomal Mechanisms

Humans have 46 chromosomes. The total number of chromosomes are divided into 23 pairs. Out of these 23 pairs, 22 are called autosomes, whereas one pair is referred to as a sex chromosome. Males and females both possess two sets of sex chromosomes. This particular combination is useful in determining a person’s biological gender. 

Male and female species differ in terms of the number or structure of their sex chromosomes (X and Y chromosomes). However, autosomes are identical in both sexes.

• All eggs would have the X chromosome as their 23rd chromosome; however, sperms might have either the X or Y chromosomes as their 23rd chromosome.
• If a sperm containing a chromosome fertilises an egg, the resulting zygote develops into a female offspring.
• If an egg is fertilised with a sperm carrying the Y chromosome, the resulting zygote develops into a male offspring.

XX Female-XY Male Type

• Both sexes have an even number of sex chromosomes in this kind of sex determination:

1. Females have two X chromosomes (XX)
2. Males have one X chromosome and one Y chromosome (XY).

• Females are homogametic (XX), producing ova (female gametes) with one X chromosome.
• Males are heterogametic, producing two distinct types of sperms (male gametes). During gametogenesis 50% sperms contain X chromosome and 50% sperms contain Y chromosome.
• During fertilisation, when X ova are fertilised with X sperm, XX females are produced; when X ova are fertilised with Y sperm, XY males are produced.
• This XX female/XY male sex determination process is found in humans, Drosophila, and plants.
• Various species have different chromosomal mechanisms for determining sex.

Sex Determination in Plants

Animals have sex chromosomes, whereas plants have autosomes (sex chromosomes). Sex determination mechanisms in plants vary significantly from species to species and even between genera. The term angiosperm refers to flowering plants. Monoecious plants have unisexual male and female flowering parts on the same plant. A dame flower is a monoecious plant with both male and female parts. 

Monoecious or bisexual plants are more common than dioecious or unisexual plants. Although monoecious plants lack a distinct sex chromosome, their ova and pollen are formed by histological differentiation. The chromosome contains the genetic information determining sex. 

Conclusion

Sex refers to the difference in genetics between two members of the same species. Thus, an individual can be either male or female under normal circumstances. Scientists have revealed that definite sex determinants, also known as heterosomes, are used to transmit sex. The sex chromosomes are found in both male and female cells in the human body. A woman possesses two X-chromosomes, whereas a man has one X- and one Y-chromosome. This indicates that the sperm cell type that fertilizes the egg determines the sex of the baby. When an egg is joined with a sperm containing a Y-chromosome, a male zygote develops; when an egg is joined with sperm with an X-chromosome, a female zygote develops.