Genetic Disorders
(1) Autosomal Genetic Disorder :
- Down’s syndrome or Mongolesm
- Cri-du-chat syndrome
(2) Sex chromosome – linked genetic disorder
- Turner’s syndrome
- Klinefelter’s syndrome
Definition : Any disorder which results due to chromosomal aberration: addition or deletion of chromosome referred as genetic disorder.
Introduction : Genetic disorder which results due to chromosomal aberration called chromosomal disorder. Very common, amongst it is Autosomal genetic disorder includes Down’s syndrome and Cri-du-chat synelrome and sex-chromosome linked genetic disorder.
Down’s Syndrom : Tri Somy
Causes :
During meiosis, at anaphase when paired homologous chromosomes
(21st chromosome) fail to separate (called non – disjunction) then, it results in meiotic abnormality seen in higher age mother’s with age 35 to 40 years.
As a result, an individual has 47 chromosomes instead of 46.
Clinical Symptoms : Affected children have a broad forehead, short neck, flat hands with stubby fingers, open maeth, Projecting lower lip with long extending tongue, and are mentally retarded. Child resembles mongoloid with slanting eyes and flat nose.
- Cri – du – chat – syndrome
Cause : Results due to deletion of one arm of the 5th autosome.
Clinical Symptoms : During this syndrome, small weak infants, shows mewing cry like eats.
Characteristics Microcephaly (small head), broad face and saddle nose, widely spaced eyes, unique facial features with physical and mental retardation.
- Klinefelter’s syndrome : ( 44 – XXY)
Such persons have 47 chromosomes with one extra X – chromosome i.e. 22 + 22 + XXY (with barr body additional) There may be the greater number of X chromosomes 44 + XXX4 (with 2 barr body) in interphase.
Clinical Symptoms : Characterized by male genitalia with abnormally small testis
(containing few (if any) nature sperms) Body hair is underdeveloped and breasts are often large by usual standard of a male.
- Turner’s Syndrome : (44 + XO)
Cause : Karyotypic studies showed that genotype of female has 45 chromosomes (leaking one x Chromosome)
Condition : (44 + XO)
Clinical Symptom : Steride females, with poorly developed ovaries and underdeveloped breasts, no oogenesis and menstrual cycle, infertility, webbing of neck heavy neck muscles.