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Primary sex determination is the determination of the gonads. In mammals, including humans, primary sex determination is strictly chromosomal and is not usually influenced by the environment. [ 1 ] Hence, the gonads are usually indicative of the biological sex.
Some chromosomal sex determination systems in animals. A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. [1] Most organisms that create their offspring using sexual reproduction have two common sexes and a few less common intersex variations.
Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. In the absence of a Y chromosome, the fetus will undergo female development. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. [5]
The development of both is controlled by sex hormones produced by the body after the initial fetal stage where the presence or absence of the Y-chromosome and/or the SRY gene determine development. Male primary sex characteristics are the penis, the scrotum and the ability to ejaculate when matured.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
A sex-determination system, a biological system that directs the development of sexual characteristics in an organism; Sexual differentiation in humans; Sexual differentiation, the development of sexual characteristics in sexually reproducing organisms in general
The tertiary sex ratio is equivalent to the adult sex ratio (ASR), which is defined as the ratio of adult males to females in a population. [ 10 ] [ 11 ] The operational sex ratio (OSR) is the ratio of sexually active males to females in a population, and is therefore derived from a subset of the individuals included when calculating the ASR ...
Sex determination generally occurs by the presence or absence of a Y chromosome in the 23rd pair of chromosomes in the human genome. Phenotypic sex refers to an individual's sex as determined by their internal and external genitalia and expression of secondary sex characteristics. [1] Sex differences generally refer to traits that are sexually ...