Genetics for UG students as from first half of Genetics chapter in Park book for community medicine. thank you.

1. Genetics & Health- I

2. Importance …
Infectious
disorders
Nutritional
diseases
control

3. Importance
• 2300 hereditary diseases
• 25-40% of all cases treated by
health services
• Explain incidence ,cause and
clustering of cases in populations

6. GENETICS
• Definition: The
study of heredity
and its variation.
• Endogenous factors
of health and
disease
• Interaction
between nature
and nature

7. THANKS TO…..
Gregor J. Mendel
Sir Francis Galton
Thomas Hunt Morgan
Sir Charles Darwin Tjio

8. CHROMOSOME
Linear strand made of DNA that carries genetic
information

9. Human Chromosomes 46
22 pairs autosomes
1 pair sex chromosomes

10. Grp-A Grp-B
Grp-C
Grp-D Grp-E
Grp-F Grp-G C G
7 Groups

11. Barr Body

12. Mitosis v/s Meiosis

13. Mitosis vs Meiosis
• Mitosis is used by single-celled organisms to reproduce; it is also used
for the organic growth of tissues, fibers, and membranes.
• Meiosis is found in sexual reproduction of organisms, and is further
broken down into meiosis I and II.

15. Mitosis

16. Meiosis

20. Chromosomes

21. • A gene is the basic unit
of heredity, made of
DNA and codes for a
specific protein
• Loci vs Alleles
• (Loci A,a,b,b ;Alleles Aa , bb)
• Homozygous (bb) vs
Heterozygous (Aa)
• Dominant (A) vs Recessive
(b)
A a
b b
Allele
A a
Allele
b b
Genes

23. • Genotype vs Phenotype
• Ex: ABO blood groups
• Polygenes
• Ex: Ht ,skin color ,refractive errors
• Penetrance: expressivity
• Responsible for skip generations

24.  Mutation: permanent change in genetic
structure
Aberrations
• Abnormality in the chromosome
• Numerical Structural
Non-disjunction
(Aneuploidy, polyploidy)
Translocation
Deletion
Duplication
Inversion
Isochromosomes
Mosaisicm

25. Non- Disjunction

29. Translocation

33. Inversion

34. Deletion

35. Gregor Mendel
and
Laws of Inheritance

36. Laws of Inheritance

37. 1. Chromosomal abnormalities
2. Mendelian disorders
3. Multifactorial disorders
4. Mitochondrial disorders
5. Non-inherited genetic disorders
Genetic disorders can be classified as

38. Chromosomal disorders
a. Sex-chromosomal b. Autosomal
•Embryonic & fetal wastage
•5.6 per 1000 live births
1.Chromosomal Abnormalities

39. a. Related to Sex-chromosomes
• Klinefelter’s syndrome
• XYY syndrome
• Turner’s syndrome
• Super female

40. 1 in 1000 males
•XXY / XXXY males
•Sterile
•Gynaecomastia
•Mental retardation
•Sons of older women
XYY syndrome
•1 in 1000 males
•Over 6ft tall
•Aggressive, antisocial
behavior
Klinefeltor’s syndrome

41. Turner’s syndrome
• 1 in 7500 live born girls
• XO female
• Infertile
• Webbed neck
• Coarctation of aorta
• Mental retardation
Super female
•XXX,XXXX,XXXXX female
•Mental retardation
•Under developed genetalia

42. • Down’s syndrome
• Patau’s syndrome
• Edward’s syndrome.
• Etc.,
b.Related to autosomes

43. Down’s syndrome
•Syn :Mongolism
•Incidence :1 in 900
(Europe)
•Defect :Extra
chromosome on 21st pair
•Trisomy 21
•Common in women
conceiving after 40 yrs
of age

44. •Mentally retarded
•Round head, tilted eye slits.
Malformed ears
•Infections
•Congenital heart disease
•Acute leukemia
•Pleasant –love music
C/F

45. 2 . Mendelian disorders
• Incidence:1% of all live births
• Inherited according to the Mendelian Laws
1,Law of unit characters
2,Law of dominance
3,Law of segregation
• Mutations at individual loci
Mendelian / single gene disorders
a.Autosomal b.Autosomal c.Sex-linked
dominant recessive

47. a.Autosomal dominant inheritance
• An individual with
autosomal dominant trait
will produce two types of
gametes-half with
normal alleles and half
with mutant gene
• Offspring of such
individual have 50:50
chance of being affected
irrespective of sex
(provided other parent is
normal)

48. • Achondroplasia
• Huntington’s chorea
• Neurofibromatosis
• Polyposis coli, familial
• Marfan’s syndrome
• Retinoblastoma
• Etc.,
Ex :

49. Achondroplasia
•Mutation in fibroblast
growth factor
receptor gene 3
•Shortening of limbs
•Large head
•Kyphosis/lordosis
•Varus/valgus
C/F

50. 2.Autosomal recessive inheritance
• Both parents should be
heterozygous
• Each offspring of such
parents has 1:4
chance of being
affected
• Occur sporadically in
outwardly normal
parents

51. Ex :
• Cystic fibrosis
• Phenylketoneuria
• Albinism
• Tay-sachs disease
• Alkaptonuria
• Fibrocystic disease of pancreas
• Haemoglobinopathies
• Etc ,.

52. Cystic fibrosis
• 2.5 to 5 per 1000 live births
• Mutant CFTR gene
• Affects respiratory system &
GIT
• Recognized and treated
earlier, life expectancy in
developed countries is about
30 yrs

53. 3.Sex linked inheritance
Sex linked traits
a. Recessive sex linked b. Dominant x-linked

54. a. Recessive sex-linked
• Mutant gene on X-chromosome in males will express readily due to
absence of normal allele while in females will not express in
presence of normal allele
• If affected male marries normal female; all daughters carriers &
sons escape
• If carrier female marries normal male;daughters-50%
carriers,50% normal:sons-50% affected,50% normal

55. Ex :
•Haemophilia A & B
•Duchenne muscular dystrophy
•Color blindness
•G-6-PD deficiency
•Hydrocephalus
•Retinitis pigmentosa
•Etc.,

56. Haemophilia
•15-20 per 100,000 males born
•Absence, decrease or reduced functioning of blood
coagulating factors VIII,IX
•Hemorrhage ,hemarthrosis
•Treatment :blood transfusions, plasma derivatives
•Threat :Hepatitis, AIDS
European Royalty with hemophiliaExcessive bruising in haemophilia

57. Duchenne muscular dystrophy
•Decreased production of
dystrophin
•Waddling gait by 1st
decade
•Progressive difficulty in
walking
•Bed ridden
•Death
•Carrier females alone
transmit the disease

58. b. Dominant x-linked
•Affected male transmits the
disease to ALL his daughters
but none of his sons
•Excess of females affected
•Ex :Vit D resistant rickets
Xg blood group
Familial
hypophosphatemia