FunMed 2: Genetics

Keywords
1. Tay Sachs: A rare disease- causes progressive damage to the CNS: normally genetically inherited
  1. Bronchopneumonia: Acute inflammation of the lungs and bronchioles
    1. Autosomal Recessive: A characteristic/condition taht only appears in individuals who have both copies of an altered gene; one from each parent
      1. Obstetrician:
        Chorionic Villus Sampling: A form of prenatal diagnosis to determine chromosomal or genetic disorders in the foetus (10-12 weeks)
        Amniocentesis: Used in prenatal diagnosis of chromosomal abnormalities & foetal infections, & also for sex determination (16 -22 weeks)
        Prenatal/ Antenatal: 'Occurring before birth'
What are the different patterns for inheritance?
1. Single Gene Disorders
  1. Autosomal Dominant
    1. Autosomal Recessive
      1. X-linked Recessive
        X- linked Dominant
        Y- linked
        Mitochondrial
        Affected males usually born to unaffected parents- mother usually asymptomatic carrier; Mainly males affected- Sons will be unaffected, daughters will be carriers; No male to male transmission; Carrier females have 50% chance of having affected son
        Duchenne Muscular Dystrophy; Haemophilia; Colour Blindness; Fragile X; Glucose 6-Phosphate Dehydrogenase Deficiency
      2. Parents of affected individuals are usually asymptomatic carriers; Affects either sex; After birth of an affected child, each subsequent child has a 25% chance of being affected; *Consanguinity
        CF; Haemochromatosis; Sickle Cell; Thalassaemia
    2. Usually at least one affected parent; Transmitted by either sex; A child w/ one affected & one unaffected parent has a 50% chance of being affected
      1. Marfan's; Huntington's; Achondroplasia; Neufibromatosis
What is Tay Sachs?
1. PNEUMONIC
  1. Testing recommended
    1. Autosomal recessive
      1. Young death (4yrs)
        Spot in macula (cherry red spots)
        Ashkenazi Jews
        CNS degeneration
        Hex A deficiency
        Storage diseae
2. A genetic disease in which hexosaminidase enzyme of lysosomes is defective (Cellular Pathology- D.J.Cook)
  1. Prevents the destruction of one type of glycolipid (GANGLIOSIDES), which then accumulates in the lyssosmes
    1. Epidemiology: Childhood form of disease high in Ashkenazi Jews (Eastern Europe): 1in 25 people being a carrier, compared to 1 in 250 in general population!
      1. S&S's: Swelling of neurones- can lead to seizures; Poor development; Blindness
        Onset: 3 to 6 months- death at ~4/5 y/o
        Rare autosomal genetic disorder
        Treatment: None yet! But experimental work is on going
3. Lysosomal Storage Disease
  1. Produced by accumulations of substrates (in this case the glycolipid- Ganglioside) which aren't metabolised because of deficiencies in lysosomal enzymes. Excess substrate leads to cell, tissue & organ dysfunction.
    1. Enzymes need to be delivered across the cell membrane & this has been achieved by modification
4. Also known as GM2 Gangliosidosis or Hexosaminidase A
  1. Results from mutations in the HEXA gene on human chromosome 15
5. ONSET
  1. Types of Tay-Sachs
    1. Classic Infantile
      1. Juvenille
        Late Onset
  2. Age of Symptoms Appearance
    1. Around 6 months of age
      1. Between 2 & 5, or anytime during childhood
        Adolescence/ early adulthood or even later
What types of Genetic Screening will the family have to undergo? And how do they work? (Benefits & Risks)
1. Chorionic Villus Sampling
  1. What: Procedure carried out to determine chromosome/ single-gene disorders. Sample of cells- CHORIONIC villi cells will be taken from the placenta
    1. When: Between 11-13th week
      1. Why: An earlier antenatal screening test suggests a possible problem. Had previous preg's w/ these problems (chromosome abnormality). Family hx of condition like CF or muscular dystrophy
        How: Transabdominal CVS- needle inserted through abdo. Transcervical CVS tube/ forceps inserted through the cervix
2. AMNIOCENTESIS
  1. What: a Diagnostic test to detect serious or potentially serious disorder in foetus.
    1. When:15-20 weeks
      1. Why:
        How: A needle is used to extract a sample of amniotic fluid. Amniotic fluid contains cells shed from the foetus that can be examined for a no. of conditions
        Conditions: (((Chromosomal)))- Down's. Edward's syndrome. Patau's syndrome. (((Blood)))- Sickle Cell Anaemia. Thalassaemia. Haemophilia.(((Neural Tube Defects))) (((Muscoloskeletal Disorders))) (((Others- Marfan's Syndrome)))
3. Factors that INCREASE the RISK of ASNORMAILITY
  1. Mother's Age
    1. Mother's Medical Hx
      1. Familt Hx of inherited genetic conditions
        Ethnic Background
4. Types of Screening
  1. Ultrasonography. Matternal Serum Screens. Embryoscopy/ Fetoscopy. Percutaneous Umbilical Cord Blood Sampling (PUBS).
    1. Molecular Genetic Tests: Look @ single genes/ short lengths of DNA taken from a person's blood/ body fluids to identify large changes in the gene
      1. Chromosomal Genetic Tests: Look @ features of a person's chromosomes (structure, arrangement, number). Parts of chromosomes may be missing, there may be extra or even be moved to a diff. part of another chromosome
        Karyotyping- a picture of all of a person's chromosomes. Identity's changes in the no. of chromosomes
        Fluorescent In Situ Hybridisation (FISH) analysis- looks @ certain parts of the chromosomes & can detect very small pieces of chromosomes that are missing/ extra
What are the Guidelines & Ethics surrounding Abortion?
1. Abortion is legal in the UK up to 24 weeks under the Abortion At 1967
  1. There is no age limit for treatment
    1. Abortions must be carried out in a hospital/ specialist licensed clinic
      1. 2 doctors must agree that an abortion would cause less damage to a woman's physical/ mental health than ontinuing the pregnancy
        24 weeks +: Necessary to save woman's life; Prevent frave permanent injury to physical/ mental health of pregnant woman; There's substantial risk that child would be born w/ serious physical/ mental disabilities
        Generally should be carried out as early as poss. Usually <12 weeks and ideally <9 weeks
        Risks: Haemorrhage (1 in 1,000); Damage to Cervix (10 in 1,000; Damage to womb (4in 1,000)
        Risks (After abortion): Infection>>> PID, Infertility, Eptopic Preg.; Miscarriages (repeated abortions)
        Procedure: Depends on stage of pregnancy- either Medication or Surgical Procedure
Cell Tissue & Structure
1. Organelles
  1. Cilia
  2. Membrane
  3. Centrioles
  4. Nucleus
    1. Chromatin (DNA complexed w/ protein). Gene Transcription- DNA to RNA. Heterochromatin/ Euchromatin. Double membrane/ Nuclear pores- regulate transport- mRNA export. Nucleolus- rRNA transcription & ribosome assembly
  5. RER
    1. Protein synthesis & transport and sorting. Ribosomes protein synthesis translate RNA into protein. Proteins made by bound ribosomes cross the rER membrane. Proteins folded & modified in ER. Sugars added- glycosylation to protect proteins
  6. Cytoplasm
  7. Lysosomes
    1. Originate @ Golgi. Contain digestive enzymes. Defence against disease. Autophagy-clean up of cell organelles. Autolysis after cell death
  8. Mitochondrion
    1. Energy production as ATP- needed for metabolic functions, apoptosis. Outer/ Inner Membrane, Cristae (increases s.a. of inner membrane), Matrix. mtDNA
  9. sER
    1. Synthesis- Carbs, Lipids. Storage (calcium). Detoxification- ER enzymes detoxify absorbs drugs toxin (liver & kidney). Modify/ detoxify hydrophobic chemicals e.g pesticides & carcinogens by converting them to more water-soluble, conjugated products
  10. G.A.
    1. Synthesis & Packaging of secretiongs (hormones/ enzymes). Packaging of enzymes w/in vesicles for cellular use. Cell membranes. Proteins tagged for delivery
  11. Peroxisome
    1. Originate @ rER. Metabolism of lipids (fatty acids). Detoxifying free radicals from normal metabolic process : hydrogen peroxide, alcohol. Liver & Kidner
2. Imaging: Microscopy (Light, Electron).
  1. Labelling Techniques: Immunocytochemistry or Immunohistochemistry

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FunMed 2: Genetics

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	Created by daniwumiash over 9 years ago