by prachee rajput Barkatullah University, Bhopal (IND)

1. DEVELOPMENT OF GONADS
Presented
by
Prachee Rajput
M.SC 4TH SEM

2. SYNOPSIS
• INTRODUCTION
• CHROMOSOMAL ORGANIZATION
• DEVELOPMENT OF BIPOTENTIAL GONADS
• MOLECULAR BASIS OF GONADIAL DEVELOPMENT
• CONCLUSION
• REFRENCES

3. INTRODUCTION
Sex is determined genetically by two chromosomes,called
the sex chromosomes.In humans and many other
mammals,the sex chromosomes are called X and Y
chromosomes.The Y chromosomes is necessary and
sufficient for the production of testis.In both sexes,the
gonads have dual function:the production of germ cells and
the secretion of sex hormones.The testes secrete large
amount of androgens,principally testosterone,but they also
secrete small amounts of estrogen.The ovaries secrete large
amount of estrogens and small amounts of androgen.The
ovaries also secrete progestrone which helps the uterus for
pregnancy.

4. CHROMOSOME ORGANIZATION
X and Y chromosomes determine the sex of humans and
many other mammals.The Y chromosomes is necessary for
the production of testis,and the testis determining gene
product is called ,SRY(for sex determining region of the Y
chromosome).SRY is a DNA binding regulatory protein.Male
cells contain X and Y chromosomes (XY pattern) where as
famale cells contain two X chromosomes (XX pattern).Each
normal ovum contains a single X chromosome,but half the
sperm contain a X chromosome and half contain Y
chromosome.When a sperm fertilizes an ovum,an XY pattern
results into genetic male.And when fertilization occurs with an
X containing spem,an XX pattern results in to genetic female.

5. DEVELOPMENT OF BIPOTENTIAL GONADS
On each side of the embryo ,a primitive gonad arises
from a genetial ridge,a condensation of tissue near
the adrenal gland.The gonad develops a cortex and a
medulla.Untill the sixth week of development ,these
structures are identical in both sexes.In genital males
the medulla develops during seventh and eight weeks
into testis,and the cortex regresses.Leydig and sertoli
cells appear and testosterone and mullarian inhibiting
substances are released.In genetic females the cortex
develops into ovary and the medulla regresses.In
normal female fetus ,mullerian duct system develops
into uterine tubes and a uterus.In male fetus wolffian
duct system develops into external genetalia.

7. MOLECULAR BASIS OF GONADIAL DEVELOPMENT
On the shorter arm of Y chromosome special gene is
present k/a SRYgene which contains a protein called
TDF(testicular determining factor) which help in
development of testis.When there are functional
testis in the embryo male internal and external
genitalia develop.Sertoli cells secrete MIS which
cause regression of the mullarian ducts.Due to
development of wolffian duct male external
genitelia develops.On the other hand in XX
chromosome,no SRY gene is present that means no
TDF protein and there fore no secretion of
MIS.Thus mullarian duct develops into female
genitelia.

8. XY XX
SRY
TDF
MEDULLA
MIF
TESTOSTERONE
TESTIS
MALE BRAIN
SRY absent
no TDF
MD
CORTEX
OVARY
ESTROGEN
FEMALE BRAIN

9. CONCLUSION
Thus from the discussion we came to know that
TDF is produced by a gene on the Y
chromosome.TDF induses the medulla of gonads to
develop the testes,which produces testosterone that
initiates the development of male sexual
characters.And in the absence of Y chromosome no
TDF is produced.The lack of TDF allows the cortex
of embryonic gonads to develop in to ovaries and in
the absence of testosterone embryo develops female
characters .

10. REFRENCES
• Review of medical physiology by william F.Ganog
• Endrocrinology by Hedly
• Internet sources