Leigh's Syndrome and Mitochondrial Diseases
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Questions and Answers

What major motor skills were lost by the child at 12 months of age?

  • Writing and drawing
  • Crawling and fine motor skills
  • Sucking and head control (correct)
  • Running and jumping

    • What condition was discovered through the MRI at 12 months of age?

  • Liver failure
  • Enlarged heart
  • Brain lesions (correct)
  • Bone fractures

    • Which theory explains the origin of mitochondria?

  • Cell Theory
  • Organic Molecular Theory
  • Endosymbiotic Theory (correct)
  • Evolutionary Theory

    • What evidence supports the Endosymbiotic Theory regarding mitochondria?

    <p>They contain DNA and divide by binary fission.</p> Signup and view all the answers

    What is one of the compartments of the mitochondria?

    <p>Intermembrane space</p> Signup and view all the answers

    What is found in the inner mitochondrial membrane that is essential for ATP synthesis?

    <p>Electron Transport Chain (ETC)</p> Signup and view all the answers

    What vision issue was noted by 18 months of age in the child?

    <p>Vision loss</p> Signup and view all the answers

    What crucial aspect of mitochondria suggests their prokaryotic origin?

    <p>Size similar to prokaryotic cells</p> Signup and view all the answers

    What respiratory problem was noted by 18 months of age?

    <p>Respiratory problems</p> Signup and view all the answers

    What is a common age range for the onset of Leigh's Syndrome?

    <p>3 months to 2 years</p> Signup and view all the answers

    What does heteroplasmy refer to in the context of mtDNA?

    <p>Presence of two or more types of mtDNA within a cell or individual</p> Signup and view all the answers

    What are some identified causes of mitochondrial diseases?

    <p>Genetic mutations in mitochondrial DNA</p> Signup and view all the answers

    Which of the following events related to mtDNA 3 parent IVF occurred first?

    <p>Successful MRT in primates</p> Signup and view all the answers

    Which of the following symptoms is commonly associated with Leigh's Syndrome?

    <p>Chronic metabolic acidosis</p> Signup and view all the answers

    What major benefit does mitochondrial replacement therapy potentially provide to parents?

    <p>Enables parents to have genetically related children free from mitochondrial disorders</p> Signup and view all the answers

    What is the prognosis for individuals diagnosed with Leigh's Syndrome?

    <p>Few months to mid-teens</p> Signup and view all the answers

    What is NOT a characteristic symptom of mitochondrial diseases?

    <p>Increased muscle mass</p> Signup and view all the answers

    What is the status of mitochondrial replacement therapy (MRT) in Canada?

    <p>Illegal under the Assisted Human Reproduction Act</p> Signup and view all the answers

    Which ethical consideration is raised regarding mitochondrial replacement therapy?

    <p>Identity and rights of the offspring</p> Signup and view all the answers

    Which enzyme deficiency is linked to Leigh's Syndrome?

    <p>Pyruvate dehydrogenase deficiency</p> Signup and view all the answers

    How common are mitochondrial diseases in the general population?

    <p>1 in 6000</p> Signup and view all the answers

    What was the maximum penalty for altering the genome of a human cell in Canada under the Assisted Human Reproduction Act?

    <p>A fine of up to $500,000 and/or a jail sentence of up to 10 years</p> Signup and view all the answers

    In Leigh Syndrome French Canadian Type, what mutation is implicated?

    <p>LRPPRC</p> Signup and view all the answers

    What process is closely associated with the symptoms of mitochondrial diseases?

    <p>Deficient ATP production</p> Signup and view all the answers

    Which of the following factors can influence the severity of mitochondrial diseases?

    <p>Genetic mutations</p> Signup and view all the answers

    What is the primary role of Complex I in the electron transport chain?

    <p>It oxidizes NADH and pumps protons.</p> Signup and view all the answers

    How many ATP molecules are theoretically produced from one molecule of glucose during oxidative phosphorylation?

    <p>36 molecules of ATP</p> Signup and view all the answers

    What is the consequence of the proton gradient generated by the electron transport chain?

    <p>It drives ATP synthesis via chemiosmosis.</p> Signup and view all the answers

    Which complex in the electron transport chain uses oxygen?

    <p>Complex IV</p> Signup and view all the answers

    Which molecule contributes to the electron transport chain through Complex II?

    <p>FADH2</p> Signup and view all the answers

    What is the function of ATP synthase in the mitochondria?

    <p>To use the proton gradient to synthesize ATP.</p> Signup and view all the answers

    What is the charge characteristic of the mitochondrial membrane potential?

    <p>Negative inside and positive outside.</p> Signup and view all the answers

    What is the primary source of electrons entering the electron transport chain?

    <p>NADH and FADH2</p> Signup and view all the answers

    Which of these processes is not a function of the mitochondria?

    <p>Protein synthesis.</p> Signup and view all the answers

    How many ATP molecules are generated from one molecule of FADH2?

    <p>2 ATP</p> Signup and view all the answers

    What is the primary energy molecule produced during cellular respiration in the mitochondria?

    <p>ATP</p> Signup and view all the answers

    Which of the following statements about glycolysis is true?

    <p>It metabolizes glucose into pyruvate.</p> Signup and view all the answers

    What role does Pyruvate Dehydrogenase (PDH) play in cellular metabolism?

    <p>It transforms pyruvate into Acetyl-CoA.</p> Signup and view all the answers

    Which statement is correct regarding the process of cataplerosis?

    <p>It is involved in biosynthetic processes.</p> Signup and view all the answers

    How does calcium homeostasis impact cellular function?

    <p>It plays a role in signaling transduction.</p> Signup and view all the answers

    What is the overall reaction for the conversion of pyruvate to Acetyl CoA?

    <p>Pyruvate + HS-CoA + NAD+ → Acetyl CoA + CO2 + NADH + H+.</p> Signup and view all the answers

    What is the significance of Acetyl CoA in metabolism?

    <p>It serves as a key substrate for the citric acid cycle.</p> Signup and view all the answers

    What is a key function of mitochondria in relation to apoptosis?

    <p>They facilitate cell death processes.</p> Signup and view all the answers

    Which pathway allows pyruvate to be used for energy in the absence of oxygen?

    <p>Fermentation.</p> Signup and view all the answers

    Which metabolic process occurs primarily in the cytosol?

    <p>Glycolysis.</p> Signup and view all the answers

    Study Notes

    Leigh's Syndrome

    • Progressive neurometabolic disorder affecting infants between three months and two years of age
    • Occurs in 1 in 77,000 births
    • Caused by at least 26 enzymatic defects, including pyruvate dehydrogenase (PDH) deficiency and respiratory chain enzyme (ETC) defects in Complexes I, II, IV, and V.
    • Characterized by deficient ATP production, severe mitochondrial defects, and cellular apoptosis.
    • No cure, prognosis is poor with life expectancy ranging from a few years to the mid-teens.

    Mitochondrial Diseases

    • Refers to a group of disorders caused by mutations in mitochondrial DNA (mtDNA) or nuclear-encoded mitochondrial proteins (nuclear DNA), leading to mitochondrial dysfunction
    • Common symptoms include insufficient ATP production, impaired calcium homeostasis, abnormal cell signaling and function, and increased cell death.
    • Affect approximately 1 in 6000 people, with symptoms ranging from mild to severe
    • Currently, no cure, but research is ongoing.

    Leigh Syndrome French Canadian Type

    • First described in the Saguenay-Lac-Saint-Jean region of Canada
    • Estimated to occur in 1 in 2000 live births, with approximately 1 in 23 individuals carrying the mutation (possible founder effect)
    • Characterized by chronic metabolic acidosis, hypotonia, facial dysmorphism, and delayed development
    • Caused by mutations in the LRPPRC gene, a protein involved in the stability of mitochondrially-encoded mRNAs.

    Heteroplasmy and Mitochondrial Disease Severity

    • Heteroplasmy refers to the presence of more than one type of mtDNA within a cell or individual
    • The proportion of mutated mtDNA can determine the severity of mitochondrial diseases.

    Mitochondrial Replacement Therapy (MRT)

    • A technique involving the transfer of nuclear DNA from a mother's egg to a donor egg with healthy mitochondria
    • Successfully tested in mice since 1990
    • Successful transfer of pronuclear DNA between day 1 single-cell human embryos in 2008, resulting in normal development to the blastocyst stage
    • Successfully conducted on primates in 2009, with no detectable carryover of maternal mtDNA
    • Approved for use in the UK in 2015, with the first baby born using this method in 2017
    • Remains illegal in Canada due to the Assisted Human Reproduction Act (2004)
    • Potential benefits include allowing parents to have children genetically related to them, potentially free from mitochondrial disorders, with this protection passed on to future generations

    Ethical Considerations of MRT

    • Concerns surrounding the identity of offspring, potential for "designer babies," and the slippery slope of genetic intervention
    • The status and rights of the donor mother, as well as the possibility of long-term adverse effects that may not be immediately apparent
    • The ethical implications of implementing an experimental treatment on future generations.

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    HSS2305 Lecture 6 on Mitochondria PDF

    Description

    Explore the intricacies of Leigh's Syndrome, a severe neurometabolic disorder affecting infants with a range of enzymatic defects leading to mitochondrial dysfunction. This quiz also covers general mitochondrial diseases, their symptoms, and the ongoing research efforts aimed at understanding these complex conditions. Test your knowledge about these critical health issues that impact ATP production and cellular function.

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