RT Book, Section
A1 Spinner, Nancy B.
A1 Conlin, Laura K.
A2 Kasper, Dennis
A2 Fauci, Anthony
A2 Hauser, Stephen
A2 Longo, Dan
A2 Jameson, J. Larry
A2 Loscalzo, Joseph
SR Print(0)
ID 1120790670
T1 Chromosome Disorders
T2 Harrison's Principles of Internal Medicine, 19e
YR 2014
FD 2014
PB McGraw-Hill Education
PP New York, NY
SN 9780071802154
LK accesspharmacy.mhmedical.com/content.aspx?aid=1120790670
RD 2022/07/07
AB Alterations  of  the  chromosomes  (numerical  and  structural)  occur  in  about  1%  of  the  general  population,  in  8%  of  stillbirths,  and  in  close  to  50%  of  spontaneously  aborted  fetuses.  The  3  ×  109  base  pairs  that  encode  the  human  genome  are  packaged  into  23  pairs  of  chromosomes,  which  consist  of  discrete  portions  of  DNA,  bound  to  several  classes  of  regulatory  proteins.  Technical  advances  that  led  to  the  ability  to  analyze  human  chromosomes  immediately  translated  into  the  revelation  that  human  disorders  can  be  caused  by  an  abnormality  of  chromosome  number.  In  1959,  the  clinically  recognizable  disorder,  Down  syndrome,  was  demonstrated  to  result  from  having  three  copies  of  chromosome  21  (trisomy  21).  Very  soon  thereafter,  in  1960,  a  small,  structurally  abnormal  chromosome  was  recognized  in  the  cells  of  some  patients  with  chronic  myelogenous  leukemia  (CML),  and  this  abnormal  chromosome  is  now  known  as  the  Philadelphia  chromosome.