What will be the phenotypic sex of a human with the followin

What will be the phenotypic sex of a human with the following genotypes? Also indicate whether testosterone levels are low or high at 6 weeks of fetal development in each individual. a. XY with the SRY gene deleted b. XY with the SRY gene located on an autosomal chromosome c. XX with a copy of SRY gene on an autosomal chromosome d. XO with a copy of SRY gene on an autosome e. XXY with the SRY gene deleted f. XXYY with one copy of the SRY gene deleted g. XY with androgen insensitivity

Solution

a. XY with the SRY gene deleted- The phenotypic sex of the human is female. And no testosterone is produced. Because SRY gene determines the male characteristics and testes development, lack of this gene causes the loss of male characteristics.

b.XY with SRY gene located on an autosomal Chromosome- The phenotypic sex of the human is male. Independent of the location of the SRY gene its function is to trigger the testes development. So even if the SRy gene is present on the autosomes it helps in the male sex determination. In this case Testes are developed. Also testosterone is produced , but in low amounts in 6 months of fetal stage.

c.XX with a copy of SRY gene on autosomal chromosome- The phenotypic sex of human is male.This condition is termed as XX male syndrome, it is caused due to unequal crossing over in male parent where SRY gene is transferred to X chromosome. During fertiliztion when female chromosome X and Male X chromosome combines , the SRY gene on male X chromosome determines the male characteristics and the human develops testes but are very small and he is sterile. Testosterone is produced at very little quantities.

d.XO with a copy of SRY gene on an autosome: The phenotypic sex of human is a male. This type of condition is called as turners syndrome.Here the individual lacks a chromosome completely or partially. In the above given case even though there is a lack of chromosome the SRY gene is present on autosomes, so the human becomes male. And testosterone is produced but at low levels.

e.XXY with SRY gene deleted: The phenotypic sex of human is female. This is because SRY gene is completedly deleted. So testes are not developed and no testosterone produced.

f. XXYY with one copy of SRY gene deleted: The phenotypic sex of human is male.In this case only one copy of the gene is deleted which might be present on Y. So there is another Y chromosome which has SRY gene that can determine the male characteristics . Also these males have small testes which are not capable of producing testosterone.

g.XY with androgen insensitivity: The phenotypic sex of human is female. In this case androgen which determines the testes development is lacking so the human looses the male characteristics. No testosterone produced.

For all the individual who are males, the testosterone developed in the 6th month of fetus development is less.