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How is the Sex of the Baby Determined?

Last Updated : 25 May, 2022
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Adolescence is the time period of a human being between being a child and an adult. It is usually between the age of 10-17 years. In this stage, the human body goes through many physical and internal changes in its body. Females develop secondary sexual characteristics like breast, and body curves while the male body develops masculine appearance like beard, deep voice, body hair, and height.

During this stage, the body experiences all these changes because of the recreation of sex hormones like estrogen, and testosterone. This marks the onset of puberty. 

Sex Determination 

Reproduction in humans is a sexual type of reproduction, in which intercourse between sexually mature males and females should take place for successful fertilization. For the fertilization to take, sperm from a mature male should come in contact with the ovum (egg) of the mature female. The fusion of sperm and egg called fertilization occurs in the fallopian tube and causes the formation of the embryo. The sex of the embryo is determined at the time of fertilization and cannot be altered/changed later on.  

Human has 23 pairs of chromosomes out of which 22 pairs of a chromosome are called autosomal chromosomes and the 23rd pair is the sex chromosome which determines the sex of the human. The male sex chromosome is XY and the female is XX chromosome. Male form two types of gametes-X and Y while females will have the same two gametes – X and X. 

Chromosome of male- 22+XY

Chromosome of female- 22+XX

The male gamete containing chromosome X or Y will fuse with the female gamete containing the X chromosome to form a zygote. If the Y gamete of male fuses with the female X gamete, the zygote is XY (male) while if the X gamete of male fuses with the female X gamete, the zygote is XX (female). Hence, the male is actually responsible for the sex of the baby, not the mother. 

Sex Determination


Determination of Baby

The sex of a baby mainly depends on the male sperm, i.e. which sperm of the male fertilizes the egg. If Y sperm of a male fertilizes the egg, then the embryo develops into a baby boy and if with X sperm then the baby girl.

Sex Prediction Method

There are various methods to find out the sex of the fetus, from which some are more reliable than others. 

  1. Amniocentesis: In this method, a needle is inserted into the amniotic sac and takes some amniotic fluid in the needle carries the genetic makeup of the embryo. Then the genetic analysis is done of the fluid and sees what autosomes (sex chromosomes). It has a high risk to the baby
  2. Non-invasive parental Testing: It is a low-risk method, in this method they use cell-free DNA to check the chromosome of the fetus and get to know about the sex chromosome.
  3. Traditional Understood: Ultrasound mainly happens for the checkup of the baby’s health in 18 weeks to 22 weeks of pregnancy. During this, the developed genital parts of the fetus can be seen which tells about the sex of the fetus.

Conceptual Questions

Question1: Define the term adolescence.


It is the time period of a human being between being a child and an adult. It is usually between the age of 10-17 years. In this stage, the human body goes through many physical and internal changes in its body. 

Question 2: List of changes that occur at puberty in the human body. 


Increase in Height, Change in body shape, Voice, Body hair, development of sex organs like testis in males and ovaries in females, reaching emotional and mental maturity.

Question 3: What are the secondary sexual characters in males and females at puberty?


Development of breast and body curves in females and growth of body hair like on chest, beard, and appearance of Adam’s apple.

Question 4: What are the sex hormones responsible for the onset of puberty?


Testosterone in males and estrogen in females.

Question 5: Who determines the sex of the baby?


The Male/Father(sperm) is responsible for the sex of the baby.

Question 6: What is the chromosomal makeup of a female and a male?


Male- 22+XY, Female- 22+XX

Question 7: How many chromosomes are present in human cells?


 23 pairs of chromosomes or 46 chromosomes are present in a human cell.

Question 8: How many sex chromosomes are present in human cells?


2 chromosomes or 1 pair of chromosomes are sex chromosomes in human cell.

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