edit this is the powerpoint slide he is talking about 4 Kary

edit: this is the powerpoint slide he is talking about

4. Karyotype of a male fetus is 46,XX, and his genotype for the X-linked gene A is Aa What could be the cause of the male phenotype of this fetus? (You can use the posted PPt on sex determination on Documents/MyBB. More than 130 cells of this fetus have been studied and they all had phenotype \'a\" Hence, it is concluded that this fetus would not show phenotypic mosaicism for gene A. Assuming this is the fact, and her mother and the fetus\'s born sister both are Aa, but phenotypically mosaic for gene A, give a reason (except random X-inactivation) that has made this fetus not to have phenotypic mosaicism for gene A. Knowing that the probability that the next child of this family would have the same situation as this fetus is close to zero, explain the reason for such a low probability? a. b. c.

Solution

A. The cause for the male phenotype in the fetus is due to translocation of the SRY gene.

In humans there are 23 pairs of chromosomes of which 22 are referred to as the autosome while the 23 pair is referred to as the sex chromosomes as they are responsible fore the determnation of the sex .If the sex chromosomes have double dose of X i.e if the off sporing recieves two X chromosome then it would be female and it is male if there is one X and one Y chromosome.

The Sry gene are responsible for male character are located on the Y chromosome when these are translocated to the X chromosome thogh geneotypically the off spring is XX it receives male characters and results in 46 XX syndrome where in the off spring develops male characters.

b.The fetus would not show phenotypic mosaicsm for the gene A is due to the effect of translocation of the Sry gene on to the X chromosome.