Question

1. Describe the phenotype of an individual with the following condition: XY chromosomes, mother exposed to large amounts of a DHT receptor antagonist during critical window of sex development in pregnancy. Include: gametes, internal genitalia, and external genital

2. Describe a mechanism that could cause an individual to develop testes, external male genitalia, and both internal female and internal male genitalia.

Answer 1

46 XY syndrome:

• It is also called as gonadal dysgenesis.Phenotype is a set of observable characteristics in the individual.So it leads to hypogonadism in a person who have karyotype 46,XY.
• It begins at early stage of development during fertilisation of gametes.
• Healthy mother is a carrier because exposed to Dihydroxytestosterone blockers leads to deficiency in 5 alpha reductase
• DHT generally provides prominent male characteristics to the embryo.As it is getting blocked affected people generally develop normal female external genitalia, and identified as female.
• But the person is externally female with functionless gonads and they will not experience puberty.
• This is mainly because of discordance between a person’s genetic sex and changes occur in external genitalia and internal sex ducts at birth and complete androgenic synthesis disorder.
• They also exhibit underdeveloped male external genitalia and bilateral cryptorchidism.
• The gonads are generally testes because of phenotype due to influence of Y chromosome thus they does not have ovaries and eggs.

Mechanism:

Mullerian ducts generally develop into the female internal genitalia (uterus,Fallopian tubes,etc) and with the help of SRY gene external genitalia can be developed.And for developing male characteristics anti mullerian and wolffian ducts receives signals from NR5A1, Wnt4 and Wt1, M33 ,Gata4 inorder to develop male genitalia. Generally testosterone is converted into DHT by the 5-alpha reductase enzyme.If this enzyme is affected the external male genitalia do not develop properly.In same way a functional androgenic receptor required for DTH inorder to regulate development of internal male genitalia.Generally only partial development are seen when both male and female development occurs in same individual.Some are dominantly expressed and some are recessively expressed.