Determination of Sex
Determination of Sex
Sex Determination: A person can have either a male sex or a female sex. The process by which sex of a newborn individual is determined is called sex determination. There are different strategies by which sex is determined in different species. In some species, environmental factors are important in determining the sex of the developing individual.
In human beings, sex is determined by genetic inheritance. Genes inherited from the parents determine whether an offspring will be a boy or a girl. Genes for all the characters are linearly arranged on chromosomes. These include the genes for sexual characters. Generally, characters related to the reproductive system are called sexual characters and those that are not are called vegetative characters. The chromosomes that carry genes for sexual characters are called sex chromosomes, while those that carry genes for the vegetative characters are called autosomes.
A sex chromosome that carries the genes for male characters is called Y chromosome and one which carries the genes for female characters is called X chromosome. We have a total of 46 chromosomes. Half of them come from the mother and the rest, from the father.
Out of these 46 chromosomes, 44 are autosomes and 2 are sex chromosomes. The sex chromosomes are not always a perfect pair. In females there are 44 autosomes and two X chromosomes. In males there are 44 autosomes, one X chromosome and one Y chromosome. So the chromosomes in woman are 44+ XX, while the chromosomes in man are 44+ XY.
All children obtain either chromosome from both parents. Females have a perfect pair of sex chromosome (homogametic) and thus, contribute X-chromosome to both the sexes of progeny but males have a mismatched pair (heterogametic) in which one is X (normal sized) and the other is V-chromosome (short in size).
Hence, an egg fertilised by X carrying sperm results in a zygote with XX, which becomes a female and if an egg is fertilised by Y carrying sperm, it results in a XY zygote that becomes male. Thus, the sex of the children will be determined by what they inherit from their father. A child who inherits an X-chromosome will be a girl and one who inherits a V-chromosome will be a boy.
Role of environment in sex determination: Environmental conditions such as temperature around the developing embryo may determine sex in some animals. Such conditions may override the genetic basis, Some animals such as snails can even change their sex, showing that their sex is not genetically determined. Incubation of the eggs of the turtle Chrysema picta at a high temperature produces females. But the incubation of the eggs of the lizard Agama agama at a high temperature produces males
How many chromosomes are present in a human gamete? | |||
| Right Option : B | |||
| View Explanation | |||
What determines the sex of an individual? | |||
| Right Option : A | |||
| View Explanation | |||
The number of autosomal chromosomes present in human beings is ______________ | |||
| Right Option : B | |||
| View Explanation | |||
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