Variable Severity of a Mitochondrial Disease Different...

Name: Problem 22, Chapter 19: Principles of Biochemistry
Uploaded: 2021-05-12T21:56:10-08:00
Duration: 5 min 25 s
Channel: Rashmi Gondi
Description: Variable Severity of a Mitochondrial Disease Different individuals with a disease caused by the same specific defect in the mitochondrial genome may have symptoms ranging from mild to severe. Explain why.

Variable Severity of a Mitochondrial Disease Different individuals with a disease caused by the same specific defect in the mitochondrial genome may have symptoms ranging from mild to severe. Explain why.

Key Concepts

Heteroplasmy

Heteroplasmy refers to the coexistence of both normal and mutated mitochondrial DNA within a single cell or organism. Since the proportion of mutant mtDNA can differ among cells, tissues, and individuals, it results in varied levels of mitochondrial dysfunction. This variability can lead to a range of symptoms from mild to severe, even when the genetic mutation is the same.

Threshold Effect

The threshold effect is the concept that a cell or tissue will function normally until the proportion of mutant mitochondrial DNA exceeds a certain critical level. Once this threshold is surpassed, impaired energy production leads to cellular dysfunction and the onset of symptoms. Differences in how close cells are to this threshold across individuals explain the variability in disease severity.

Transcript

00:01 Quickly try to understand the mechanism behind mitochondrial inhibitor.

00:06 The dna molecules, the mitochondrial dna molecules are the same, but one of the offspring gets a very mild form of a disease and another offspring gets clinically affected.

00:21 It gets severely affected.

00:23 Why is this? let's understand why does this happen? why is the question? very interesting question.

00:32 The transmission of disease causing the mitochondrial dna from heteroplasmic mother to offspring shows high degree of genetic and phenotypic variability between the siblings.

00:47 Like i have said, like i have already said, while i was explaining the question to you, it shows variability among the offsprings.

00:58 One of the, as you can see in the picture or the diagram here also, as you can see in the picture or the diagram here also, so one of the child gets easily affected, another offspring.

01:07 It has a mild phenotype, mildly affected, no much symptoms.

01:12 So not actual disease.

01:14 But the dna is there.

01:17 But it's the same mitochondrial dna, but no, it is not shown.

01:24 It's not phenotypic.

01:25 So very mild disease symptoms or the features of the disease are not shown.

01:32 But again you see that another child, is again clinically affected why does this happen why is this degree of the variability of the disease from mild to severe amongst the siblings so this variability is very well explained by a phenomenon known as mitochondrial genetic bottleneck so is the term that you need to understand mitochondrial genetic bottleneck in this lecture we are going to going to learn about this very mechanism.

02:12 So, mitochondrial genetic bottleneck.

02:15 The comparison of heteroplasmic level in the offspring with those oo sites at different stages of the development has revealed that the bottleneck occurs in the early stages of the eugenic...

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