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Genetics

Genetics is the study of heredity, genes, mutations, and diseases. Learn about alleles, chromosomes, mutations, and Mendelian inheritance patterns.

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Genetics

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  1. Genetics

  2. WHAT IS GENETICS????? The branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms

  3. Terminology: • Gene. • Alleles- Dominant. - Recessive. • Nucleotides. • Codon. • Genetic Code.

  4. GENE Biological unit of heredity. Gene hold the information to build and maintain their cells and pass genetic traits to offsprings In cells, a gene is a portion of DNA

  5. Gene (DNA) RNA formation Protein formation Cell structure Cell enzymes cell function

  6. ALLELE Is one member of a pair or series of different forms of a gene. Homozygous-an organism in which 2 copies of genes are identical i.e. have same alleles Heterozygous-an organism which has different alleles of the gene

  7. Chromosomes: • Chromatin: DNA, RNA & proteins that make up chromosme • Chromatids: one of the two identical parts of the chromosome. • Centromere: the point where two chromatids attach • 46 chromosomes. 22 pairs Autosomes and 1 pair Sex chromosomes.

  8. NUCLEOTIDE: group of molecules that when linked together, form the building blocks of DNA and RNA; composed of phosphate group, the bases:adenosine,cytosine,guanine and thymine and a pentose sugar.In case of RNA,thymine base is replaced by uracil. CODON: series of three adjacent bases in one polynucleotide chain of a DNA or RNA molecule which codes for a specific amino acid. GENETIC CODE: the sequence of nucleotides in a DNA or RNA molecule that determines the amino acid sequence in the synthesis of proteins.

  9. Congential Disease. Diseases which are present at birth. Hereditary/Familial Disease. Diseases which are derived from one’s parents and transmitted in the gametes through the generations. Not all congenital diseases are genetic( congenital Syphilis) and not all genetic diseases are congenital (Huntington disease).

  10. Mutations.

  11. Definition: Permanent changes in the DNA. Those that affect germ cells are transmitted to the progeny. Mutations in the somatic cells are not transferred to the progeny but are important in the causation of cancer and some congenital diseases.

  12. CAUSES OF MUTATIONS • Chemicals • Nitrous acid • Alkylating agents • 5- bromouracil • Antiviral drug iododeoxyuridine • Benzpyrene in tobacco smoke

  13. X – rays & ultraviolet light Certain viruses such as bacterial virus

  14. Types Of Mutations.

  15. Point Mutation: Substitution of a single nucleotide base by a different base. Categorized as: Transition transversion MissenseMutations. NonsenseMutations.

  16. Frameshift Mutations: Insertion or deletion of one or two base pairs alters the reading frame of the DNA strand.

  17. Trinucleotide Repeat Mutations: set of genetic disorder caused by trinucleotide repeat in certain genes exceeding normal,stable threshold e.g. Fragile X Syndrome.

  18. Classification Of Genetic Diseases: Single Gene Defects/Mendelian Disorders. Disorders with Multifactorial or Polygenic inheritance. Cytogenetic Disorders. Disorders showing atypical patterns of inheritance.

  19. Mendelian Disorders A genetic disease caused by a single mutation in the structure of DNA, which causes a single basic defect with pathologic consequences

  20. Patterns Of Inheritance: Autosomal Dominant. Autosomal Recessive. X-Linked Recessive. X-Linked Dominant.

  21. Autosomal Dominant Disorders.

  22. Manifested in heterozygous states. • Individuals with these diseases usually have one affected parent .* • Variable to late onset. • These disorders usually involve non-enzymatic proteins; • Proteins involved in metabolic pathway regulation. • Structural Proteins.

  23. Inheritance Pattern: Typical mating pattern is a heterozygous affected individual with a homozygous unaffected individual. Every child has one chance in two of having the disease Both sexes are affected equally..

  24. Disorders:

  25. Structural Protein Defects: Marfan’s Syndrome. Ehler-Danlos Syndrome.

  26. Marfan’s Syndrome: Mutation in the fibrillin gene. Fibrillin important component of microfibrils in Elastin. Tissues affected are Skeleton, Eyes and the CVS. C/F include tall stature, long fingers, pigeon breast deformity, hyper-extensible joints,high arched palate, BL subluxation of lens, floppy Mitral valve, Aortic aneurysm and dissection, defects in skin,lungs.

  27. Ehler-Danlos Syndrome(Cutis Hyperelastica): Characterized by defects in collagen synthesis. .Clinical Features include fragile, hyper-extensible skin, hyper-mobile joints, grotesque contortions, rupture of internal organs like the colon, cornea and large arteries, poor wound healing.

  28. Defects in metabolic pathway proteins: • Familial Hypercholesterolemia: • One of the most common mendelian disorders. • Mutation in the LDL receptor gene. • Hypercholesterolemia due to impaired LDL transport into cells. • Increased risk of atherosclerosis and coronary artery disease. • Increases Cholesterol leads to formation of Xanthomas.

  29. Autosomal Recessive Disorders

  30. Largest group of Medelian Disorders Affected individuals usually have unaffected (carrier) parents. Uniform, early age of onset. These disorders usually involve Enzymatic Proteins.

  31. Pattern Of Inheritance: Typical mating pattern is two heterozygous unaffected (carrier) individuals. The triatdoesnot usually affect the parent, but siblings may show the disease Siblings have one chance in four of being affecte Both sexes affected equally.

  32. Disorders:

  33. Glycogen Storage Diseases.

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