More common Y chromosome

1 more common

1.1 y chromosome microdeletion
1.2 defective y chromosome
1.3 xxy
1.4 xyy

more common

no vital genes reside on y chromosome, since half of humans (females) not have y chromosome. well-defined human disease linked defect on y chromosome defective testicular development (due deletion or deleterious mutation of sry). however, having 2 x chromosomes , 1 y chromosome has similar effects. on other hand, having y chromosome polysomy has other effects masculinization.

y chromosome microdeletion

y chromosome microdeletion (ycm) family of genetic disorders caused missing genes in y chromosome. many affected men exhibit no symptoms , lead normal lives. however, ycm known present in significant number of men reduced fertility or reduced sperm count.

defective y chromosome

this results in person presenting female phenotype (i.e., born female-like genitalia) though person possesses xy karyotype. lack of second x results in infertility. in other words, viewed opposite direction, person goes through defeminization fails complete masculinization.

the cause can seen incomplete y chromosome: usual karyotype in these cases 45x, plus fragment of y. results in defective testicular development, such infant may or may not have formed male genitalia internally or externally. full range of ambiguity of structure may occur, if mosaicism present. when y fragment minimal , nonfunctional, child girl features of turner syndrome or mixed gonadal dysgenesis.

xxy

klinefelter syndrome (47, xxy) not aneuploidy of y chromosome, condition of having x chromosome, results in defective postnatal testicular function. mechanism not understood; not seem due direct interference x expression of y genes.

xyy

47, xyy syndrome (simply known xyy syndrome) caused presence of single copy of y chromosome in each of male s cells. 47, xyy males have 1 x chromosome , 2 y chromosomes, total of 47 chromosomes per cell. researchers have found copy of y chromosome associated increased stature , increased incidence of learning problems in boys , men, effects variable, minimal, , vast majority not know karyotype.

in 1965 , 1966 patricia jacobs , colleagues published chromosome survey of 315 male patients @ scotland s special security hospital developmentally disabled, finding higher expected number of patients have y chromosome. authors of study wondered whether y chromosome predisposes carriers unusually aggressive behaviour , , conjecture framed next fifteen years of research on human y chromosome .

through studies on next decade, conjecture shown incorrect: elevated crime rate of xyy males due lower median intelligence , not increased aggression, , increased height characteristic reliably associated xyy males. criminal karyotype concept therefore inaccurate.