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Medical Genetics
Introduction to Medical Genetics
Dr.Aida Fadhel Biawi , 2013
Medical Genetics
Genetics concerns the process of trait
inheritance from parents to offspring,
including the :
1- molecular structure and function of genes
2-gene behavior in the context of a cell or
organism (e.g. dominancy)
3- gene distribution and variation and
change in populations .
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A brief history:
1-The observation of Arabs , ancient
Greeks and Hebrews regard genetic
phenomena.
2- The experiments of mendel in 1865
on pea.
3- 35 years later, Darwin formulated
his theories of volution.
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4- In 1900, the principles of Mendel
rediscovered by three scientists in
three different countries.
5- Also in 1900, Landsteiner
discovered ABO blood groups.
6- In 1902 Garrod described
alkaptonuria as a( first error inborn
of metabolism )
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7- In 1909 Johannsen use the term of
gene to denote the basic unit of
hereditary.
8- Next decades, Muller demonstrated
the genetic consequences of ionizing
radiation in the fruit fly.
9- In 1944, Avery showed that genes
are composed from deoxyriboneuclic
acids DNA.
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10- In 1953 Waston and Crick they
published their paper about physical
structure f the DNA formed the basis
of what is now known as molecular
genetics .
11- The human genome project
provide the complete human DNA
sequence from 1990-2003.
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The genome refers to all of the DNA or
genetic material in an organism .
What about gene ? Allele ?
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Branches of Genetics
• Medical genetics
• Microbial genetics
• Molecular genetics
• Population genetics
• Archaeogenetic
• Psychiatric genetics
• Quantitative genetics
Medical Genetics
Medical genetics is the specialty of
medicine that involves the diagnosis
and management of hereditary
disorders.
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Microbial genetics is a subject area
within microbiology and genetic
engineering.
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Molecular genetics is the field of
biology and genetics that studies the
structure and function of genes at a
molecular level.
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Population genetics is the study of
allele frequency distribution and
change under the influence of the
four main evolutionary processes:
natural selection, genetic drift,
mutation and gene flow.
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Archaeogenetics, a term refers to
the application of the techniques of
molecular population genetics to the
study of the human past.
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Psychiatric genetics, a subfield of
behavioral neurogenetics, studies the
role of genetics in psychological
conditions such as alcoholism,
schizophrenia, and autism.
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Quantitative genetics is the study of
the inheritance of continuously
measured traits (such as height or
weight) and their mechanisms.
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What is Medical Genetics?
Medical genetics involves any application of
genetics to medical practice . .It thus
includes :
1- studies of the inheritance of diseases
in families
2- mapping of disease genes to specific
locations on chromosomes
3- analyses of the molecular
mechanisms through which genes cause
diseases
4- diagnosis and treatment of genetic
disease.
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• As a result of rapid progress in molecular
genetics , gene therapy ( the insertion of
the normal genes into patients in order to
correct genetic disease ) is now possible .
• Medical genetics also includes genetic
counseling , which involves the
communication of information regarding
risks , prognoses , and treatments to
patients and their families.
Medical Genetics
Genetic disease
A. What is genetic disorder?
A genetic disorder is a disease that
is caused by an abnormality in an
individual’s DNA. Abnormalities can
range from a small mutation in a
single gene to the addition or
subtraction of an entire chromosome
or set of chromosomes.
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Genetic disease
B. Characteristics of genetic disorders
1. congenital
2. mode of inheritance
3. population distribution
4. familial
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Genetic disease
B. Characteristics of genetic
disorders
1.
2.
3.
4.
congenital
mode of inheritance
population distribution
familial
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Down syndrome
albinism
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Genetic disease
B. Characteristics of genetic
disorders
1.
2.
3.
4.
congenital
mode of inheritance
population distribution
familial
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3 Pedigree of Genetic Disease
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Genetic disease
B. Characteristics of genetic
disorders
1.
2.
3.
4.
congenital
mode of inheritance
population distribution
familial
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x
hemophilia
（Blood clotting，to bleed）
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Genetic disease
B. Characteristics of genetic
disorders
1.
2.
3.
4.
congenital
mode of inheritance
population distribution
familial
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• Family number of genetic disease.
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Genetic disease
B. Characteristics of genetic
disorders
1.
2.
3.
4.
congenital
mode of inheritance
population distribution
familial
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Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
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Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
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Genetic disease
Single-gene disorders result
when a mutation causes the protein
product of a single gene to be
altered or missing.
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1-cystic fibrosis
2- fragile X syndrome
3- Sickle cell disease
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In Cystic fibrosis: there is a three nucleotide deletion from the
coding sequence. This will causes a deletion of Phenylalanine.
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Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
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In chromosome disorders, entire
chromosomes, or large segments of
them, are missing, duplicated, or
otherwise altered.
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Patau syndrome
Trisomy 13 -- the presence of an
extra (third) chromosome 13 in all of
the cells.
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Diagnosis &Treatment
• Diagnosis: chromosome analysis
• NO TREATMENT
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Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
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Genetic disease
Multifactorial disorders result
from mutations in multiple genes,
often coupled with environmental
causes.
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???
Influence of environment on some traits
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Obesity
How these genes interact with environmental factors ??
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Fingerprints
• Fingerprints: a polygenic trait
• Dermatoglyphics: ridges on
fingers, palm, toes, and feet
• Influenced by prenatal
environment
– Nutrition of the mother
– Rate of finger formation
and growth
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Others :diabetes, hypertension (high blood pressure),
heart-related problems, arthritis, Alzheimer’s disease or
even different cancers (breast cancer).
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Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
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Genetic disease
Somatic cell genetic diseases:
result from the altered genetic
materials in somatic cells.
Like cancer.
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Medical Genetics
Genetic disease
C. Classification of Genetic Disorders
1.
2.
3.
4.
5.
single-gene disorders
chromosome disorders
multifactorial disorders
somatic cell genetic disorders
mitochondrial disorders
Medical Genetics
Genetic disease
Mitochondrial genetic diseases:
Due to the mutation of mitochondrial
DNA. Like leber hereditary optic
neuropathy LHON .(loss of central vision )
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leber hereditary optic neuropathy LHON .
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