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