Medical Genetics Introduction to Medical Genetics Dr.Aida Fadhel Biawi, 2013.

Medical Genetics

Introduction to Medical Genetics

Dr.Aida Fadhel Biawi , 2013

Medical Genetics

Genetics Genetics concerns the process of trait concerns the process of trait inheritance from parents to offspring, inheritance from parents to offspring, including the :including the :

1- 1- molecular structure and functionmolecular structure and function of genes of genes2-gene behavior in the context of a 2-gene behavior in the context of a cellcell or or organismorganism (e.g. dominancy) (e.g. dominancy)3- gene distribution and variation and 3- gene distribution and variation and

change in change in populationspopulations . .

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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 Branches of Genetics • Medical genetics • Microbial genetics • Molecular genetics • Population genetics • Archaeogenetic• Psychiatric genetics • Quantitative genetics

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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?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 diseases4- 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.

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Genetic diseaseGenetic 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 diseaseGenetic disease

B. Characteristics of genetic disorders 1. congenital 2. mode of inheritance 3. population distribution 4. familial

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Genetic diseaseGenetic disease

B. Characteristics of genetic disorders

1. congenital 2. mode of inheritance 3. population distribution 4. familial

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albinism

Down syndrome

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Genetic diseaseGenetic disease

B. Characteristics of genetic disorders

1. congenital 2. mode of inheritance 3. population distribution 4. familial

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3 Pedigree of Genetic Disease

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Genetic diseaseGenetic disease

B. Characteristics of genetic disorders

1. congenital 2. mode of inheritance 3. population distribution 4. familial

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xx

hemophiliahemophilia （ Blood clotting ， to bleed ）

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Genetic diseaseGenetic disease

B. Characteristics of genetic disorders

1. congenital 2. mode of inheritance 3. population distribution 4. familial

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• Family number of genetic disease.

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Genetic diseaseGenetic disease

B. Characteristics of genetic disorders

1. congenital 2. mode of inheritance 3. population distribution 4. familial

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Genetic diseaseGenetic disease

C. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. mitochondrial disorders

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Genetic diseaseGenetic disease

C. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. mitochondrial disorders

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Genetic diseaseGenetic 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 fibrosis1-cystic fibrosis 2- fragile X syndrome 2- fragile X syndrome3- Sickle cell disease3- 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 diseaseGenetic disease

C. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. 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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Medical GeneticsPatau syndromePatau syndrome  

Trisomy 13 -- the presence of an extra (third) chromosome 13 in all of the cells.

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Diagnosis &TreatmentDiagnosis &Treatment• Diagnosis: chromosome analysis

• NO TREATMENT

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Genetic diseaseGenetic diseaseC. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. mitochondrial disorders

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Genetic diseaseGenetic disease

Multifactorial disorders result from mutations in multiple genes, often coupled with environmental causes.

Medical GeneticsInfluence of environment on some traits

???

Medical Genetics Obesity Obesity

How these genes interact with environmental factors ??

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FingerprintsFingerprints

• 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 diseaseGenetic disease

C. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. mitochondrial disorders

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Genetic diseaseGenetic disease Somatic cell genetic diseases:

result from the altered genetic materials in somatic cells.Like cancer.

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Genetic diseaseGenetic disease

C. Classification of Genetic Disorders

1. single-gene disorders 2. chromosome disorders 3. multifactorial disorders 4. somatic cell genetic disorders 5. mitochondrial disorders

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Genetic diseaseGenetic 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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