19. *HEREDITARY:
Transmitted in the germ line; passed from parents to their
offspring.
*FAMILIAL:
Diseases run in families and represent multifactorial
inheritance. Risk for first degree is 5-10% higher.
*CONGENITAL:
Born with; disease present since birth.
20. BARR BODY
[ SEX CHROMATIN ]
Nucleus
Barr body
# of Barr bodies = # of X chromosomes - 1
31. LYON HYPOTHESIS:
[ 1961, Mary Lyon ]
1. Only one of the X - chromosomes is
genetically active,
2. Other X of either maternal or
paternal origin undergoes
heteropyknosis and is rendered
inactive.
32. 3. Inactivation of either the maternal or
paternal X occurs at random among all
the cells of the blastocyst on or about
the 16th day of embryonic life.
4. Inactivation of the same X
chromosome persists in all the cells
derived from each precursor cell.
LYON HYPOTHESIS:
33.
34. INCIDENCE:
• 1 in 800 live births [ overall ]
• Maternal age:
•< 20 yrs - 1 in 1550,
•> 45 yrs - 1 in 30
35.
36.
37.
38.
39. Flat face
Protruding tongue
Occiput tends to be flat
Low bridged nose
Oblique palpabral
fissure
Epicanthic folds
Slanting eyes
Brushfield spots in iris
43. 40%- Congenital cardiac defects
ASD, VSD, TOF, PDA.
10-20 fold risk to develop Acute leukemia's:
ALL/AML.
CNS:
Mental retardation, IQ -30.
Develop Alzheimer’s disease -
-- at very young age;
Intestine:
Imperforate anus, duodenal stenosis, Hirschsprung’s
disease.
Sterility:
Arrested spermatogenesis.
44. Life expectancy:
Most common cause of death:
Congenital heart diseases and leukemia.
With normal heart, only 5% of children with
Down syndrome die before age 10.
After age 10, the estimated life expectancy
is 55 years.
45.
46. Common cause of male hypogonadism
and infertility.
1 in 1000 live male births,
Presence of one or more extra X
chromosome, 47 XXY.
Rarely diagnosed before puberty,
47. Clinical features:
Eunuchoid body habitus:
– Long legs, tall and thin.
Small, atrophic testes, small penis.
Lack of secondary sexual characteristics,
Deep voice of high pitch.
Gynecomastia, feminine characters.
IQ - low; mental retardation, behavioral
abnormality.
52. Turner Syndrome:
Most common sex chromosome
abnormality in females,
Monosomy X; the missing chromosome X
is usually of paternal origin.
Incidence: 1/8000 . Most die in infancy
76. 76
Class I Loss of receptor synthesis
Class II Transport inside cell is impaired
Class III Failure of receptors to bind LDL
Class IV Fail to internalize after binding
Class V Internalized bodies are trapped in
endosomes
77. 77
MUTATION IN ENZYME PROTEIN
PHENYLKETONURIA
GALACTOSEMIA
LYSOSOMAL STORAGE DISEASES
GLYCOGEN STORAGE DISEASES
