lec 4 SAQ - Mitochondrial Genetics and Inherited Disorders Quiz

16,569 bp

37

93%

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

<p>Several different individuals</p> Signup and view all the answers

<p>About 3000</p> Signup and view all the answers

<p>Mitochondria are the 'powerhouses' of the cell, responsible for generating ATP and involved in cell signalling, growth, death, and cell cycle regulation.</p> Signup and view all the answers

<p>Mitochondria are thought to have originated as free-living bacteria that were taken up by eukaryotes to carry out oxidative phosphorylation.</p> Signup and view all the answers

<p>Most nucleated cells contain 500 to 2000 mitochondria.</p> Signup and view all the answers

<p>In the cone cell photoreceptor of the eye, mitochondria make up 80% of the intracellular volume.</p> Signup and view all the answers

<p>The human nuclear genome contains approximately 23,000 protein-coding genes.</p> Signup and view all the answers

<p>The human nuclear genome consists of 23 double-stranded linear chromosomes.</p> Signup and view all the answers

<p>Mitochondrial heteroplasmy refers to the variation in mtDNA sequences, either between cells (intercellular heteroplasmy) or within cells (intracellular heteroplasmy).</p> Signup and view all the answers

<p>Mitochondrial DNA is inherited almost exclusively along the maternal line.</p> Signup and view all the answers

<p>The threshold effect refers to the proportion of pathogenic mtDNA in tissues, which influences the phenotypic expression of mitochondrial diseases.</p> Signup and view all the answers

<p>MtDNA mutation represents the only source of mtDNA genetic diversity, as mitochondria do not undergo recombination during cell division.</p> Signup and view all the answers

<p>The control region of mtDNA is highly polymorphic and is useful for forensic purposes, such as in criminal investigations.</p> Signup and view all the answers

<p>Homoplasmy refers to all mtDNA sequences being the same, while heteroplasmy refers to variation in mtDNA sequences.</p> Signup and view all the answers

<p>Predicting phenotype from genotype and genetic counseling is difficult in mitochondrial heteroplasmy because the proportion of pathogenic mtDNA in tissues can vary and influence the phenotype.</p> Signup and view all the answers

<p>Mitochondrial disease often affects high-energy organ systems such as the CNS, muscles (skeletal and heart), liver, and kidney.</p> Signup and view all the answers

<p>Bilateral, painless, subacute visual failure that develops during young adult life.</p> Signup and view all the answers

<p>Males are approximately four times more likely to be affected than females.</p> Signup and view all the answers

<p>The typical symptoms of LHON include asymptomatic onset in one eye followed by similar symptoms in the other eye, bilateral visual loss, and in some cases, central vision improvement but incomplete recovery.</p> Signup and view all the answers

<p>The three point mutations of mitochondrial DNA commonly associated with LHON are m.3460G&gt;A in MT-ND1, m.11778G&gt;A in MT-ND4, and m.14484T&gt;C in MT-ND6.</p> Signup and view all the answers

<p>Individuals with the m.11778G&gt;A mutation typically have an intermediate phenotype and there is a chance of recovery.</p> Signup and view all the answers

<p>Heteroplasmy refers to the presence of both normal and mutated mitochondrial DNA in an individual. In LHON, heteroplasmy in cone cells may influence the risk of developing visual impairment.</p> Signup and view all the answers

<p>Haplogroup H is associated with higher risk of Parkinson Disease, while haplogroups J and K are associated with lower risk. Haplogroups I, J, and T are also associated with increased longevity.</p> Signup and view all the answers

<p>No, mitochondrial DNA inheritance can also occur through biparental inheritance in some exceptional cases.</p> Signup and view all the answers

<p>Leigh Syndrome is characterized by MRI necrotizing lesions in the midbrain and brainstem, bilateral symmetrical degeneration of the brain stem, cerebellum, and basal ganglia. It typically has an onset in infancy or childhood, often after a viral infection, and can involve peripheral nervous system involvement, non-neurologic abnormalities, and respiratory impairment.</p> Signup and view all the answers

<p>The estimated incidence of Leigh Syndrome is at least 1 in 40,000 births.</p> Signup and view all the answers

<p>Leigh Syndrome exhibits broad genetic heterogeneity, with mutations identified in at least 75 genes.</p> Signup and view all the answers

<p>Some of the genetic mutations associated with Leigh Syndrome include mutations in pyruvate dehydrogenase (PDHC) deficiency, respiratory chain enzyme defects in complexes I, II, IV, and V, and specific mtDNA mutations such as the NARP mutation and the MERRF mutation.</p> Signup and view all the answers

<p>Leigh Syndrome can be inherited in matrilineal (mitochondrial) pattern, de novo mutation, X-linked recessive, or autosomal recessive patterns.</p> Signup and view all the answers

<p>The different inheritance patterns in Leigh Syndrome are primarily due to the fact that most mitochondrial proteins are encoded on the nuclear genome, and mutations in these genes follow classic Mendelian inheritance rules.</p> Signup and view all the answers

<p>Mitochondrial transplantation/donation is a technique that involves the transfer of healthy mitochondria to prevent the passing on of hereditary mitochondrial diseases. It can be performed before or after fertilization and has been the subject of ethical debates, including a UK parliamentary debate in 2015.</p> Signup and view all the answers

<p>Some important factors to remember about mitochondrial genetics are: 1. Predicting phenotype from mtDNA genotype is difficult due to heteroplasmy. 2. Males affected by mtDNA-related diseases cannot transmit the disease. 3. mt Haplogroups can influence disease penetrance and severity. 4. Most Leigh Syndrome cases are caused by mutations in the nuclear genome, leading to Mendelian inheritance patterns.</p> Signup and view all the answers