Date post: | 06-Dec-2014 |
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Human Genetics & Health
Dr Mohan Lal
Associate Professor
Department of Community Medicine
Govt. Medical College, Amritsar
Over the last Few decades, a significant transition has taken place in the etiology of diseases affecting mankind
Environmentally related disorders have decreased &genetic disorders & non-communicable disorders have become a major cause of morbidity and mortality
Health of an individual is based on Uncontrollable Factors (genetics, gender,
predisposition to a disease) Controllable Factors (diet, smoking status,
exercise levels)
Genetics
Study of inheritance dealing with the transmission of hereditary characters from one generation to another.
Human genetics is concerned with the inheritance of human traits & their relationship to the human health
Deals with the herediatry disorders & provide key to their prevention &control .
Prevalence of Genetic Disorders Prevalence of genetic disorders (excluding
multifactoral genetic disease)-7/1000 live births.
Out of 7, -4 sex linked disorders -2 Autosomal disorders - other characterized by balanced or
unbalanced chromosomal rearrangements Genetic Liability in the community .
Genetic Disorders
Autosomal Dominant Autosomal Recessive Sex Linked disorders
Retinoblastoma Albinism Hemophilia
Marfan Syndrome Total color blindness Agammaglobunemia
Neurofibromatosis Phenylketouria Red green color blindness
Fibrocystic disease of Pancreas
Neonatal Jaundice
Diseases Associated with Genetic Predisposition Cancer
Coronary heart disease
Diabetes (Insulin dependent)
Alzheimer’s disease
Biological Determinant Genetics Predisposition to disease
A person may be at increased risk of inheriting a disease or condition if they have a biological parent who has had the disease.”
Genetics can have an influence on a persons risk to certain conditions or diseases.
Ex: If your parent has high cholesterol, you are at a higher risk of developing high cholesterol.
Examples of diseases – genetic predisposition Alzheimer's disease (before the age of 65)
Migraine headaches Type 1 & 2 diabetes CVD - High blood pressure, hypertension Certain cancers – (including breast and prostate)
Prevention & Control of Genetic Disorders
1. Prevention
2. Screening
3. Counseling
Prevention
Primary Prevention
(Prevent birth of an affected newborn)
Secondary Prevention
To Prevent clinical manifestations
in affected individuals by appropriate intervention
Tertiary Prevention
Provision of adequate care &rehabilitation in
affected individuals
Specific Protection
From X-Ray Early diagnosis by :-
-Detection of carriers
- Prenatal diagnostics
- Amniocentesis
-New born screening
- Pre clinical case recognition
Screening
Applied at Prenatal, Neonatal& general population levels.
Prenatal & neonatal screening –ideal approach for early diagnosis & prompt treatment of herediatry disorders
Prenatal Screening
Prenatal screening by:-
-Ultrasonography fetal malformation & fetal growth abnormalities
-Amniocentesis(14-16 weeks of pregnancy ) diagnosis of spina bifida & other neural tube abnormalities.
Chorionic villus sampling technique (10-12 weeks of pregnancy) – Both biochemical & structural abnormalities can be detected.
Neonatal Screening
Help in detecting herediatry disorders like
-Phenylketouria
-Sickle cell Anemia
-Duchene muscular dystrophy
Population Screening
To identify individuals at risk of developing herediatry disorders.
Objective:-
- To make presymptomatic diagnosis for arresting the progress of such disease by timely preventive intervention.
-Only such disorders should be Identified for which measures for prevention & treatment are available.
Genetic Counseling
Genetic counseling -an integral part of the management of patients and families with genetic disorders .
-Retrospective Counseling :- Parents who have already given birth to a child affected with genetic condition
-Prospective Counseling:-with those at high risk for genetic disorders & screens them to find out if they really are affected.
Genetic Counseling
A educational process by which patients or/& at risk individuals are given information to
understand the nature of the genetic disease, its transmission and the options open to them in
management and family planning
Essential Components of Counseling History of family background construction
Clinical diagnosis
Confirmatory diagnosis
Calculation of reoccurrence of risk
Counseling
Follow up
Genetic counseling Process
Beneficiaries :- Individual or coupleWhy?•Have affected child•Are carriers•Have genetic disease in family•Have recurrent abortions•High maternal/paternal age•Exposed to a mutagen/teratogenic•Are consanguineous
Reaching accurate diagnosis Family history
Physical/clinical examination
Cytogenetic studies/radiology
Laboratory/DNA analysis
Estimation of Recurrence Risk :-
Family pedigree Applying various
methods Risk calculation -Bayesian -Mendels
Genetic Counseling :- Available options Risk calculations New developments Disease course Treatment availability
Decision Making:- Knowledge of disease
recurrence Available options ·Family pressure ·Religious beliefs ·Social status ·Economic status ·Community influence
Gene Therapy
Means introduction of gene sequence in to cell with the aim of modifying the cell behavior in a clinically relevant fashion.
Used in many ways :- - To correct genetic mutation (as for cystic fibrosis) To kill a cell (as for cancer) To modify susceptibility (as coronary heart disease )
The gene may be introduced using a virus or by means of a lipid or receptor targeting .
Eugenics
Idea of herediatry improvement by selective breeding propagated by Galton.
Can be defined as improvement of human species or race by selective breeding .
Positive Eugenics:- Applied to animals for increasing milk & have better
quality animals. Improving yield of grains Genetic manipulation for human welfare & survival Negative Eugenics example “purify” German race by
eliminating genetically poor individuals.
Euthenics
Means providing appropriate / suitable environments for genotype to express themselves fully.
Euthenics measures must be comprehensive to include physical,intellectual,social & cultural components whereby genetically disadvantaged individuals can achieve a reasonable degree of development
Measures to improve the environment in order to improve health, appearance, behavior, or well-being of society.
Lead an independent existence.
Genetic Services Medical termination of Pregnancy 1971 lays down
legislative framework of application of genetics science PC-PNDT act 1974- Sex Selective abortions need to be eliminated by
implementation of PC-PNDT Act. Antenatal clinics provide opportunity to educate
individual & family on genetics. Screening of Antenatal mothers for Rh grouping Avoidance of teratogenic drugs & radiation Promoting immunization against rubella before
pregnancy is preventive genetics.
Contraception for limiting the size of family & bearing children at right age is a example of positive & preventive genetics.
Improving nutritional status & consuption of Iron & folic acid
Use of ultrasonography to detect defective children is essentially a good screening activity.
Early childhood development services in ICDS programme by providing environmental stimuli is an attempt to realize full potential of genetic endowment of young children.
Thank You