MALE SEX DETERMINATION PAX 2 EMX2 INSR, IGF1R SEI GATA4 /FOG2 IRR, POD1 DAXI? me
ID: 272513 • Letter: M
Question
MALE SEX DETERMINATION PAX 2 EMX2 INSR, IGF1R SEI GATA4 /FOG2 IRR, POD1 DAXI? mesoderm DAKI WNT4 RS#01 Vanin-1, Nexin-1 FONLZ Sertoli cell TESTIS Ro Leydig cell Part of the HUMAN sex determination pathway is shown above. For A-D, circle the statements that are true and correct the statements that are false. Arrows between genes indicates activation, -l indicate repression. A. Men do not have dosage compensation. B. In X0 and XXX women, the X:A ratio are 1:1 and 3:1, respectively. C. XX human males can arise from non-disjunction during meiosis. D. XYY humans show no dosage compensation. E. Four brothers in a family were found to be 46, XX, sry-; there was no trace of the Y chromosome (including sry) anywhere in their genomes. There are also no mutations in the promoter, repressorlenhancer elements, or coding region of the Sox9 gene. In ONE sentence, suggest where a mutation has occurred in the sex determination pathway to give rise to the four 46, XX, sry- brothers. F. Suppose that there is a RARE case of a fertile 46, XX, sryt male. In ONE sentence, what will be the sex and genotype of the children this male can have?Explanation / Answer
a) True, men are 44+XY and have only one X-chromosome which is euchromatic
b) False, X0 (44 + X0) X:A ratio = 1:2 while XXX (44 + XXX) X:A ratio = 3:2
c) False, XX males can arise due to a mutation in SF1 or SRY translocation to other chromosome or over-activation of sox9
d) True, XYY has euchromatic X-chromosomes
e) The gain-of-function mutation in the SF1 present on chromosome 9 can cause 44+XX into males. It activates both AMH pathway and testosterone synthesis.
f) 50% children will be male with genotype 44+XX sry+ and 50% will be female with 44+XX
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