2. GENETIC DISORDER
Mendelian disorders
• alteration or mutation in
the single gene
• transmitted to the offspring
• can be traced in a family by
the pedigree analysis
• Examples -
• Haemophilia, Cystic fibrosis,
Sicklecell anaemia, Colour
blindness, Phenylketonuria,
Thalassemia
Chromosomal disorders
• due to absence / excess /
abnormal arrangement of one
or more chromosomes
• Failure of segregation of
chromatids in cell division
cycle results in the gain / loss
of a chromosome(s), called
Aneuploidy
• Down’s Syndrome
• Klinefelter’s Syndrome
• Klinefelter’s Syndrome
7. Haemophilia
• Sex linked recessive ( X- Linked) disease
• Non stop bleeding due to one defected gene
responsible for blood clotting .
• The Queen Victoria was a carrier of the disease.
10. Sickle-cell anaemia
• Autosome linked recessive trait
• The disease is controlled by a single pair of allele, HbA and HbS.
• Cause- substitution of Glutamic acid (Glu) by Valine (Val) at the sixth
position of the beta globin chain of the hemoglobin molecule.
• The shape of the RBC from biconcave disc to elongated sickle
shaped
11. The mutant hemoglobin molecule
undergoes polymerization under low oxygen
tension causing the change in the shape of the
RBC from biconcave disc to elongated sickle
like structure
12. Sickle cell anemia / symptoms and effect
- swelling of the hands and feet
- Fatigue or extreme tiredness
- jaundice.
- delayed growth
- episodes of pain
15. Phenylketonuria
• This inborn error of metabolism.
• Autosomal recessive trait.
• The affected individual lacks an enzyme that
converts the amino acid phenylalanine into
tyrosine.
• Phenylalanine is accumulated and converted into
phenylpyruvic acid in brain results in mental
retardation.
• These are also excreted through urine because of
its poor absorption by kidney.
16.
17. Thalassemia
• autosome-linked recessive blood disease
• reduced rate of synthesis of one of the globin chains
(alpha and beta chains) that make up haemoglobin.
• formation of abnormal haemoglobin
• resulting into anaemia which is characteristic of the
disease.
18.
19. • TYPES
• Alpha Thalassemia- production of Alpha globin
chain is affected. It is controlled by two genes
HBA1 and HBA2 on chromosome 16 of each
parent.
• Beta Thalassemia- production of beta globin chain
is affected. It is controlled by a single gene HBB on
chromosome 11 of each parent.
• Thalassemia - quantitative problem
• sickle-cell anaemia - qualitative problem
Thalassemia
20. Cystic fibrosis
Autosomal recessive
disorder of infants.
Cause - recessive autosomal
allele chromosome 7
It produces a defective
glycoprotein.
formation of thick mucus in
skin, lungs, pancreas, liver
eand other secretory
organs.
22. Chromosomal Disorders
• Due to absence or excess or abnormal arrangement of
one or more chromosomes
• Aneuploidy - Failure of segregation of chromatids during
cell division cycle results in the gain or loss of a
chromosome(s)
• Polyploidy - increase in a whole set of chromosomes
• Down’s Syndrome
• Klinefelter’s Syndrome
• Turner’s Syndrome
23. Down’s Syndrome
CAUSE –trisomy of
chromosome number 21
First desribed by - Langdon
Down (1866).
Features - short statured with
small round head,
furrowed tongue, partially
open mouth
• Palm is broad with palm
crease.
• Physical, psychomotor and
mental development is
retarded.
24. Klinefelter’s
Syndrome
Cause- Karyotype of 47,
XXY.
Features - masculine
development,
however, the feminine
development
(development of
breast, i.e.,
Gynaecomastia)
Such individuals are
sterile.
25. Turner’s
Syndrome
Cause – Karyoytpe
45 with X0
Features - Such
females are sterile
as ovaries are
rudimentary.
• lack of other
secondary sexual
characters
