sex determination and differentiation in human with development and differentiation of gonads. this presentation helps you in understanding the concept of sex at genetic level.

1. Gonad and sex
differentiation
Submitted by:
Anshul Kushwaha
M.Sc. 2nd sem
Submitted to:
Dr. Kiran Singh

2. “In order to maintain the flow of
life on Earth and to ensure the
inheritance of an entire
species, the procreation of
offspring is the responsibility of
each living organism.

3. The two main categories in which humans and most
other living things are divided based on their
reproductive functions and production of gametes.
These sexes and their gametes are designated as male
and female.
sex
Mammals have partial physiological and biochemical
differences between the sexes from each other, favoring
the production and development of different gametes
within different sexes.

4. Genetic sex
According to chromosome
constitution of fetus
Gonad
development
According to presence or absence of
SRY gene
Development of external
and internal genitalia
According to presence or absence of testicular
hormones
At time of
fertilization
~6 weak of
fertilization
According to presence of individual
gonad
Development of
secondary sexual
characters
After
puberty
(Gonadal sex)
Sexual differentiation
in humans
In fetus

5. Genetic sex
Sperm 22[Y]
zygote 44[XY]
Egg 22[X] male
Sperm 22[X]
zygote 44[XX]
Egg 22[X] female
Determined by the chromosome constitution of sex chromosome pair in embryo.
● Female: - 44[XX], homogametic sex because the sex chromosomes are both X
chromosomes.
● Male: - 44[XY], presence of one Y and one X chromosome as sex chromosome pair
thus heterogametic sex.

6. Gonads are primary reproductive organs and primary component of sex determination.
In both sexes the gonads are derived from common somatic mesenchymal tissue precursors called
the genital ridge primordia.
Gonad development and differentiation complete in two phases
Gonadal sex
● Initial Phase/development phase:-
The early development of the gonads is indistinguishable in males and females. Bipotential
gonads apparently identical and can form either ovaries or testes. This period is therefore called
indifferent or bipotential phase of gonadal development.
● Secondary phase/differentiation phase:-
After the development of the identical genital ridge, these genital ridges develop in the testis or
ovary according to the presence or absence of the SRY gene.

7. genital ridge primordia
Testis
( Precursors of Indifferent
gonad)
Indifferent gonad
Ovary
Absence of SRY gene
Development
phase
Differentiation phase
Differentiation of gonads

8. Phenotypic sex
Main phenotypic difference:
● Male external & internal genitalia
● Female external & internal genitalia
● Secondary component of sex determination.
● Each sex has a sex specific size, Vocal cartilage, physiology and musculature.
● Physiology of individual favor the production and development of different gametes
within different sexes .
● Differentiation depends on presence or absence of testicular hormones.

9. Differentiation of internal genitalia
There are two separate sets of primordia for male and female internal genitalia, each of
which is unipotential and located in the mesonephros adjacent to the developing gonad, and
are called as-
• Wolffian or mesonephric duct
• Mullerian or paramesonephric duct.
In presence of testicular hormones
Wolffian duct develop into:-
● Epididymis,
● Vas deferens,
● Seminal vesicles,
( male internal genitalia)
In absence of testicular hormones
mullerian duct develop into:-
● Oviducts,
● Uterus,
● Upper vagina,
( female internal genitalia)

10. Differentiation of external genitalia
The primordia of the external genitalia are bipotential and differentiate into external
genitalia of male or female according to presence or absence of testicular hormones.
Development of male external genitalia
● Fusing of urethral folds,
● Formation of scrotum by fusing genital
swellings in midline,
● Formation of glans penis by genital
tubercle expanding.
Development of female external genitalia
● clitoris formation by genital tubercle,
● formation of the labia minora and majora,
● urethral folds and genital swellings remain
separate.

11. Female Characters:-
● Breasts develop,
● Hips and thighs widen,
● Pubic and underarm hair develop,
● The ovaries start to produce eggs,
● Menstruation starts,
● Fat deposits mainly around
the buttocks, thighs and hips.
These are usually determined by steroid hormones secreted from the gonads which affect the
behavior and physiology.
Most physiological changes show after a certain age to ensure that mating will only occur
between different sexes at time of maximum fecundity.
Secondary sex characteristics
Male Characters:-
● Voice breaks,
● Hair grows on the face and the body,
● Body becomes more muscular
● Genitals are develop,
● Sperm are produced,
● Enlargement growth of the penis,

12. Male embryo
Degeneration of
mullerian duct
Testis development
Sertoli cells
Laydig cells
Development of
internal genitalia
Production of AMH
(anti mullerian hormone)
Development of
internal genitalia
Development of
secondary sexual
charectersProduction of
androgen
Development
of male
(From wolffian duct)
44[XY}

13. Female embryo
Spontaneous degeneration of
wolffian duct
ovary development
Development of
internal genitalia
Development of
external genitalia
Development of
secondary sexual
charecters
Development
of female
( from mullerian duct)
44[XX]

14. WT 1
LHX 9
EMX 2
SF 1
SRY
Sox9
Sf1
Genes for male differentiation
Rspo1
Wnt4
Dax1
Foxl2
Genes for female differentiation
Fgf9
Dmrt1
Genes for indifferent gonad
Gene envolve in gonad differentiation
Development phase Differentiation phase

15. Thanks!