48 Questions
Which of the following is NOT a function of mitochondria?
Transcription and translation of mitochondrial genes
How many genes are encoded on the mitochondrial genome?
37
Which of the following is NOT a component of the electron transport chain?
ATPase
What is the main cause of ROS accumulation in mitochondria?
Uncoupling of generation and consumption of O2
Which type of DNA is primarily responsible for inherited disorders of mitochondria?
nuclear DNA
How many mitochondrial gene products are needed to produce ATP?
90
How many genes on the mitochondrial genome encode for non-mRNA products?
24
Which part of the cell synthesizes most mitochondrial proteins?
Cytoplasm
Which organelle is known as the 'powerhouse' of the cell?
Mitochondrion
What is the approximate number of mitochondria found in most nucleated cells?
500 to 2000
In which type of cell do mitochondria make up 80% of the intracellular volume?
Cone cell photoreceptors
How many protein coding genes are there in the human nuclear genome?
23,000
What percentage of the human nuclear genome is composed of 'protein coding' sequences?
1.5%
How many genes are there in the mitochondrial genome?
37
What is the term used to describe the inheritance pattern of mitochondria?
Matrilineal
What is the term used to describe the phenomenon where an individual has a mixture of normal and mutant mitochondrial DNA?
Heteroplasmy
Which organ systems are especially affected by mitochondrial diseases?
Nervous system and cardiovascular system
What is the main source of genetic diversity in mitochondrial DNA?
Mutation
What is heteroplasmy?
Variation in mtDNA sequences
What is the main difference between homoplasmy and heteroplasmy?
Homoplasmy is when all mtDNA sequences are the same, while heteroplasmy is variation in mtDNA sequences
What is the relationship between mtDNA mutations in somatic cells and heritability?
MtDNA mutations in somatic cells are not heritable
What is the term for a high proportion of pathogenic mtDNA in oocytes?
Genetic bottleneck
What is the main factor that influences the phenotypic expression of mitochondrial diseases?
The proportion of pathogenic mtDNA in tissues
What is a characteristic of diseases associated with mtDNA mutations?
Different mtDNA mutations can result in the same disease
What is the main source of inherited disorders of mitochondria?
Changes in nuclear DNA
Which of the following is a characteristic of Leber Hereditary Optic Neuropathy (LHON)?
It is a painless visual failure that develops during young adult life.
What is the main factor that influences the risk of developing mitochondrial diseases?
mtDNA Haplogroups
Which of the following is NOT a characteristic of mitochondrial diseases?
Inheritance from the father
What is the main source of genetic diversity in mitochondrial DNA?
mtDNA Haplogroups
Which organ systems are especially affected by mitochondrial diseases?
All of the above
What is the term used to describe the phenomenon where an individual has a mixture of normal and mutant mitochondrial DNA?
Heteroplasmy
Which of the following is the most common age of onset for Leigh Syndrome?
Infancy
What is the estimated incidence of Leigh Syndrome in births?
1 in 40,000
Which genetic defect is associated with the NARP mutation?
MERRF mutation
What is the most likely pattern of inheritance for Leigh Syndrome?
Autosomal dominant
What is the main source of genetic diversity in mitochondrial DNA?
Haplogroups
What is the term used to describe the phenomenon where an individual has a mixture of normal and mutant mitochondrial DNA?
Heteroplasmy
What is the main factor that influences the phenotypic expression of mitochondrial diseases?
Haplogroups
What is the term used to describe the process of mitochondrial transplantation or donation?
Three-parent embryo
What is the main cause of ROS accumulation in mitochondria?
mtDNA mutations
Which symptom of LHON is most likely to improve over time?
Gradual improvement in central vision
Which point mutation of mitochondrial DNA is generally most common in Asians and Caucasians with LHON?
m.11778G>A in MT-ND4
Which statement about heteroplasmy in LHON is true?
Heteroplasmy of A and m.14484T>C mutations arose on haplogroup J background
Which disease has been found to be higher among individuals with mtDNA haplogroup H?
Parkinson disease
Is there an equivalent for the male line to mitochondrial DNA?
Yes, the Y chromosome
Is mitochondrial DNA inheritance exclusively matrilineal?
No, there are exceptional cases where paternal mitochondrial DNA could be passed to the offspring
What symptom was NOT present in the 2-year-old boy, Kevin, with Leigh Syndrome?
Palpable liver
What diagnostic finding was NOT observed in the 2-year-old boy, Kevin, with Leigh Syndrome?
Positive family history of Leigh Syndrome
Study Notes
Mitochondrial Functions and Characteristics
- Mitochondria are not responsible for transcription and translation of nuclear genes.
- Mitochondrial genome encodes 37 genes.
- Mitochondrial gene products are necessary for producing ATP.
Mitochondrial DNA and Inheritance
- Mitochondrial DNA is primarily responsible for inherited disorders of mitochondria.
- Mitochondrial DNA is inherited exclusively through the maternal line.
- The term used to describe the inheritance pattern of mitochondria is maternal inheritance.
- Heteroplasmy is a mixture of normal and mutant mitochondrial DNA in an individual.
- The main source of genetic diversity in mitochondrial DNA is mutations in the mitochondrial genome.
Mitochondrial Diseases and Characteristics
- Mitochondrial diseases are especially prevalent in the nervous and muscular systems.
- The main factor that influences the phenotypic expression of mitochondrial diseases is the proportion of mutant mitochondrial DNA.
- A characteristic of diseases associated with mtDNA mutations is variable expressivity.
- The main source of inherited disorders of mitochondria is mitochondrial DNA mutations.
Specific Mitochondrial Diseases
- Leber Hereditary Optic Neuropathy (LHON) is a characteristic of mitochondrial disease.
- The main factor that influences the risk of developing mitochondrial diseases is the proportion of mutant mitochondrial DNA.
- Leigh Syndrome is a mitochondrial disease with a most common age of onset in infancy.
- The estimated incidence of Leigh Syndrome in births is 1 in 40,000.
- The genetic defect associated with the NARP mutation is a mitochondrial DNA mutation.
Mitochondrial Function and ROS
- The main cause of ROS accumulation in mitochondria is electron transport chain dysfunction.
- Mitochondrial transplantation or donation is described as mitochondrial replacement therapy.
Miscellaneous
- Mitochondria make up 80% of the intracellular volume in oocytes.
- The approximate number of mitochondria found in most nucleated cells is 100-1000.
- The human nuclear genome consists of 20,000-25,000 protein coding genes.
- The percentage of the human nuclear genome composed of 'protein coding' sequences is 1.5%.
Test your knowledge on mitochondrial genetics and inherited disorders in this quiz. Learn about heteroplasmy and how it affects the phenotype of mitochondrial disease. Understand the matrilineal inheritance pattern of mitochondria.
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