Short and descriptive information about the most common type pf genetic disorders.

2. In recent years, a large number of human
diseases, deformities and disorders have been
found to be hereditary.
The various genetic disorders can be
grouped under two broad categories-
1. Mendelian disorders and
2.Chromosomal disorders
The above disorders can further be classified
into the following categories:

3. Mendelian disorders
Autosomal
Dominant gene
mutation
Autosomal
Recessive gene
mutation
Sex-linked
Recessive
1.Polydactyly 1.Alcaptonuria 1.Haemophilia
2.Huntington’s disorder 2.Sickle cell anaemia 2.Duchenne’s muscular
dystrophy

4. Chromosomal disorders
Autosomal disorders Sex-chromosomal
disorders
1.Down’s syndrome 1.klinefelter’s syndrome
2.Edward syndrome 2.Turner’s syndrome

5. Mendelian disorders
 A congenital physical anomaly in human.
 It occurs due
 Results as an irregularity in the process of
formation of hand
 One single finger splits into two.
 More than usual number of fingers on hand or
foot.

6. Picture 1.a: polydactyly on feet
Picture 1.b: on hand
1.a
1.b

7. Also known as Huntington's chorea, is an inherited disorder.
 Due to mutation in either of an parent's two copies of a
gene called
 This gene provides the genetic information for a
) triplet repeats in the gene
coding for the Huntingtin protein results in an abnormal
protein, which gradually
 jerky, random, and uncontrollable movements called chorea.
may be initially exhibited as general restlessness,
small unintentionally initiated or uncompleted motions &
lack of coordination.

8. Picture 2: showing the most affected regions i.e., the basal
ganglia region due to Huntington’s disorder

9. It is an inborn metabolic disorder
produced by the action of a single gene.
 Due to lack of normal gene that controls the synthesis of
the enzyme , which catalyse the
breakdown of in liver.
 Homogentisic acid accumulates and is excreted in urine.
 Blackening of urine on exposure to air.
 Darkening of certain cartilages.
 It also causes mild arthritis.

10. Picture 3.a: A-normal urine; B-alcaptonuric urine
Picture 3.b: Hands of a severely affected alcaptonuric
person.
3.a
3.b

11. .
 Can be transmitted from parents to offspring when both
the partners are carrier for the gene.
 Controlled by a single pair of gene.
 Due to substitution of at the 6th
position of molecule.
 The oxygen carrying capacity of blood cell decreases.
 RBC becomes sickle shaped. Surface area decreases.
 Extremely painful, causing abdominal, chest and bone pain,
fatigue, shortness of breath, delayed puberty etc.

12. Picture 4: showing RBC of a normal man and a
affected man

13.  First reported by .
disease which shows its
transmission from
 Affects only male child.
 caused by the gene, say h located in the
.
 Lack of blood clotting factor (i.e., factor VIII).
 Haemophiliacs bleed excessively when injured.
 A seriously affected person may bleed to death even
after minor skin cut.

14. Picture 5: HAEMOPHILIA (THE BLEEDING CONDITION)

15. Also known as Duchenne Muscular Dystrophy.
It is a disorder.
a group of
 Due mutation of gene on , hence fails to produce
a protein called .
 Dystrophin is thought to relay the nerve’s signal to the
in the muscle cell, as a result is not
released and
 Progressive muscular wasting.
 Poor balance.
 Scoliosis (curvature of the spine and the back).
 Progressive inability to walk.
 Limited range of movement.
 Muscle spasms.

16. Picture 6.a: Normal muscle
picture 6.b: In affected muscle the tissue
has become disorganized and the
concentration of dystrophin (green) is
greatly reduced.
6.a 6.b
6.c
Picture 6.c: showing difference
between normal and affected
muscles tissue.

17. Chromosomal disorders
Chromosomal disorders are caused due
of one or more
chromosomes.
Failure of segregation of chromatids during cell
division cycle results in the gain or loss of a
chromosome(s) is called

18. First reported by Langdon Down in 1866. But actual
cause was identified by Lejeune and his co-workers.
trisomic, extra chromosome no.21 is
present i.e.,
 Due to during oogenesis in the
mother’s ovary.
 Rounded face, broad forehead, a Mongolian type of
eyelid fold, furrowed tongue & partially open mouth.
 Palm is broad with characteristics palm crease.
 Physical, psychomotor and mental retardation.

19. Picture 7.a: Showing a boy with Down’s syndrome
Picture 7.b: Feet of a boy with the disorder.
7.a 7.b

20.  Due to the presence of all or a part of a
, hence also known as .
 Most cases of this disease occur due to problems during
the formation of the reproductive cells or during early
development.
 Heart defect.
 Small head.
 Small or abnormal jaw.
 Clenched fist with overlapping fingers.
 Malformed legs.

21. Picture 8.a and 8.b showing babies affected with
Edward’s syndrome
8.a
8.b

22.  Due to the presence of an
resulting into karyotype of
 This genotype results from the union of a
and .
 Sterile male with small testes.
 unusually long legs.
 Obesity.
 Sparse body hair.
 And many female characteristics such as breasts.

23. Picture 9.a and 9.b: showing a person with
klinefelter’s syndrome
9.a 9.b

24.  It is an with a single sex
).
(i.e., total no. of chromosome is 45)
 Due to union of an abnormal egg with a normal X
sperm or a normal X egg and an abnormal O sperm.
 Sterile female.
 Underdeveloped breasts.
 Rudimentary ovaries.
 Small uterus.

25. Picture 10.a: A girl with Turner’s syndrome
picture 10.b: Clinical features of an individual affected with
the disorder.
10.a 10.b

26. Conclusion:
We have learned that there are a number of genetic
disorders that can affect the human population which
can vary in causes, severity and characteristics.