Eugenics, behavioural genetics and genetic disorders

1. EUGENICS, BEHAVIOURAL
GENETICS AND GENETIC
DISORDERS
SANDESH G M
2016610811
I M.SC GPB
TNAU. MADURAI

2. EUGENICS
• Eugenics is a set of beliefs and practices that aims
at improving the genetic quality of the human population.
• It was derived from Greek word “Eugenes” which means
‘well-born’.
• The Term Eugenics was coined by Sir Francis Galton.

3. FATHER OF GENETICS
• Charles Davenport, Founder of the Eugenics
Record Office, credited with the popularization
of eugenics.
• Relied heavily on Mendel’s work.
• Respectable studies on eye color, hair color,
hair texture, and pigmentation.

4. TYPES OF EUGENICS
• Positive Eugenics:
It is the improvement of human genetic traits through the
promotion of higher rates of sexual reproduction for people with desired traits.
• Negative Eugenics:
it is the reduced rates of sexual reproduction and sterilization of people with
less desired or un-desired traits.

5. APPROACHES USED
• Positive Eugenics:
1. Artificial insemination by donor.
2. Egg donation.
3. Embryo selection.
4. Genetic engineering.
5. Gene therapy.
6. Cloning.
7. Prenatal diagnosis of genetic disorders and pregnancy terminations of defective fet
uses.

6. APPROACHES USED
• Negative Eugenics:
1.Incentives for sterilization.
2.Better contraceptives.
3. Sterilization.
4. Abortion.

7. BEHAVIOURAL GENETICS
• Behavioural Genetics is the field of study that examines the role of genetic and
environment influences on behaviour.
• In humans, this information is often gathered through the use of genetic association
studies or family including the twin study or adoption study.
• In animal studies breeding, transgenesis are common.

8. ANIMAL STUDIES
• In animal research selection experiments have often been employed.
1.Laboratory house mice have been bred for open field behavior.
2.Thermoregulatory nesting.
3.Voluntary wheel running behavior.

9. HUMAN STUDIES
Quantitative genetic modelling of individuals with known genetic relationships
allows one to estimate to what extent genes and environment contribute to
phenotypic differences among individuals.
e.g., Sibling, Dizygotic and Monozygotic twins.
• Twin study
1. Monozygotic twins share 100% of their genome.
Difference is due to difference in their environment.
2. Dizygotic twins share, on average, 50% of their segregating genome.
Difference is due to both environment and genes.

10. CONCLUSIONS FROM BEHAVIOURAL
GENETIC RESEARCH
1.All behavioural traits and disorders are influenced by genes.
2.Environmental influences tend to make members of the same family more different,
rather than more similar.
3.The influence of genes tends to increase in relative importance as individuals age.

11. CONTD..,
• Genetic influences on behaviour are pervasive.
The single largest source of evidence comes from twin studies, where it is
routinely observed that monozygotic (identical) twins are more similar to one another
than are same sex dizygotic(fraternal) twins.
• Nature of environmental influence.
Monozygotic twins are genetically identical but are never perfectly concordant
for psychiatric disorder or perfectly correlated for behavioural traits, indicates that the
environment shapes human behaviour.

12. GENETIC DISORDERS
• What is a genetic disorder?
A genetic disorder is a genetic problem caused by one or more abnormalities in
the genome, especially congenital.
Genetic disorders may be hereditary.
Some may be by new mutations or changes to DNA.
Eg: Cancer

13. TYPES OF DISORDER
Single- gene disorders
• Autosomal dominant
• Autosomal recessive
• X-linked
• Y-linked
• mitochondrial
Many genes disorders
• Asthama
• Cancers
• Hypertension
• Obesity
• Heart diseases

14. SINGLE GENE DISORDERS
1.Autosomal dominant :
Only one mutated copy of the gene will be necessary
for a person to be affected.
Each affected person usually has one affected parent.
The chance a child will inherit the gene is 50%.
Eg: Huntington’s disease, Neurofibromatosis type I

15. HUNTINGTON’S DISEASE
• Huntington's disease (HD) is an inherited, degenerative brain disorder which results
in an eventual loss of both mental and physical control.
• The disease is also known as Huntington's chorea. Chorea means "dance-like
movements" and refers to the uncontrolled motions often associated with the
disease.
• Produces incorrect protein that eventually
leads to destruction of brain cells
• Initial symptom occurs in those aged 30-50.

16. • Autosomal recessive :
Two copies of the gene must be mutated for a person to be affected.
An affected person usually has unaffected parents who each carry a single copy of
the mutated gene.
Eg: sickle cell anemia, cystic fibrosis, phenylketonuria etc.,

17. SICKLE CELL ANEMIA
• An inherited, chronic disease in which
the red blood cells, normally disc-
shaped, become crescent shaped.
• As a result, they function abnormally
and cause small blood clots.
• These clots give rise to recurrent
painful episodes called "sickle cell pain
crises".
• Sickle cell disease is most commonly
found in African American
populations.

18. CYSTIC FIBROSIS
• Monogenic
• Caused by deletion of only 3 bases on chromosome 7.
• Blockage of airways, pancreatic ducts, biliary ducts.
• Fluid in lungs, potential respiratory failure.
• High level of sodium in the sweat - "salty“
• Hypovitaminosis A, D, E, K, poor weight gain.
• 1:2000 live births - most common lethal genetic disease in white population.

19. PHENYLKETONURIA
• PKU is a metabolic disorder that results when the PKU gene is inherited from both
parents.
• Caused by a deficiency of an enzyme which is necessary for proper metabolism of
an amino acid called phenylalanine.
• Phenylalanine is an essential amino acid and is found in nearly all foods which
contain protein, dairy products, nuts, beans.
• Brain damage can result if the diet is not followed causing mental retardation and
mousy body odor (phenylacetic acid is in sweat).

20. X-LINKED DISORDERS
• X-linked disorders are caused by the mutation in genes on the x chromosome.
• Some of the x-linked disorders are
1.Klinefelter syndrome
2.Turners syndrome
3.Hemophilia
4.Colour blindness

21. KLINEFELTER SYNDROME
• Disorder occurring due to nondisjunction of the X chromosome.(47, XXY)
• The Sperm containing both X and Y combines with an egg containing the X, results
in a male child.
• The egg may contribute the extra X chromosome and forms XXY.
• Little body hair is present, and such person are
typically tall, have small testes.
• Infertility results from absent sperm.
• Evidence of mental retardation may or
may not be present.

22. HEMOPHILIA
• Caused by the inheritance of one
recessive gene on the X (males) or two
recessive genes on both X’s (females).
• Affects blood – blood does not clot.
• Leads to severely increased risk of
bleeding from common injuries.
• Potentially fatal.

23. TURNER SYNDROME (45, X0)
• 1:3000 females.
• primary hypogonadism in phenotypic female.
• Turner syndrome is associated with underdeveloped ovaries, short stature, webbed,
and is only in women.
• Bull neck, and broad chest. Individuals are sterile, and lack expected secondary
sexual characteristics.
• Mental retardation typically not evident.

24. Y-LINKED DISORDERS
• These are also called as Holandric disorders caused by mutations on Y chromosome.
• Eg: Hypertrichosis
This is the very tragic disease called Hairy Ears.
Y-linked trait are rare.
Only one cured is known

25. THANK YOU….,