پاورپوینت کروموزوم (pptx) 25 اسلاید
                                    
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                                    تعداد اسلاید: 25 اسلاید
 
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                                    کروموزوم 
Aneuploidy
As women age 
some chromosomes exhibit non-disjunction in oocytes
Many theories why
13, 18, 21 associated with age
16 and X only first meiotic division associated with age 
Most chromosome abnormalities incompatible with life
Will miscarry
Maternal age specific estimates of trisomy among all clinically recognisable pregnancies
Hassold et al., 1985
Parental origin of aneuploidy
				Paternal %		Maternal %
Trisomy 13			15			85
Trisomy 18			10			90
Trisomy 21			5			95
45,X				80			20
47,XXX			5			95
47,XXY			45			55
47,XYY			100			0	
Chromosome abnormalities in humans
Spermatozoa				10%
Mature oocytes				25%
Spontaneous miscarriage		50%
Live births					0.5-1%
Most due to maternal meiotic non disjunction
Strongly related to maternal age
Natural selection at work
Chromosome abnormalities in miscarriages
			  Incidence %
Trisomy 13				2
Trisomy 16				15
Trisomy 18				3
Trisomy 21				5
Other Trisomy			25
Monosomy X			20
Triploidy				15
Tetraploidy				5
Other 				10
Chromosome abnormalities in newborns
				
				Incidence / 10,000 births
Trisomy 13				2
Trisomy 18				3
Trisomy 21				15
45,X					1
47,XXX				10
47,XXY				10
47,XYY				10
Unbalanced				10
Balanced				30
Total					90
Triploidy
Trisomy 16
Trisomy 13 &18
Trisomy 21 
Klinefelters
45X 	
lethal
Most common in spontaneous miscarriages
Completely lethal. Cause unknown 
95% miscarry 
80% miscarry 
50% miscarry 
1% at conception	
98% miscarry, probably mosaic survive
Chromosome abnormalities
                                            7               
                     6  
                3         
2
  1            
2
        4 
                                                           5                                             
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