47 Questions
Which genetic material has a higher number per cell?
Nuclear genome
What is the primary role of PGC-1α in mitochondrial biogenesis?
Regulation of the process via the environment
Why is genetic counseling challenging for mitochondrial diseases?
Due to the observation of every type of inheritance pattern
Why is genomic (mt and nDNA) used as a first-line tool in diagnosing primary mitochondrial diseases?
To justify the diagnosis based on genetic evidence
How are haplotypes in mitochondrial inheritance named?
Using gel electrophoresis
When did Eve's mitochondria and her peopling of the world start?
200,000 years ago
Which haplogroup has the most genetic diversity?
L3
Where did the M haplogroup mostly populate?
South Asia
When did M and N divergents populate the Americas?
15,000 years ago
How are mitochondria inherited?
Maternal inheritance
When are no new mitochondria synthesized during embryonic development?
During cleavage
What is the main process for efficient ATP synthesis in most cell types?
Oxidative phosphorylation
What allows mixing of mtDNA copies for cells with heteroplasmic mitochondria?
Fusion
Where are most mitochondrial proteins synthesized?
Cytoplasm
In terminally differentiated cells, mitochondrial number is increased by increased energy demand through activation of what?
Transcription of genes involved in energy metabolism
Apart from energy metabolism, what other processes are mitochondria involved in?
Non-shivering thermogenesis
What stimulates mitochondrial number in differentiated cells?
Increased energy demand
Which factor can activate transcription for mitochondrial biogenesis?
High cytosolic calcium
What causes loss of mitochondria, mostly in damaged or low functionality mitochondria?
Mitophagy
What can alter the activity of PGC-1α downstream targets?
Post-translational modification
Which type of genetic diseases of mitochondria are caused by dysfunction resulting from mtDNA and nDNA variants?
Both mtDNA and nDNA variants
What is the prevalence of genetic diseases of mitochondria in children?
About 6/100,000
What causes complicated inheritance patterns in mitochondrial diseases?
Variants in nuclear and mitochondrial genes
What can mtDNA variants differ wildly between?
Different cell types
Which syndrome can be caused by maternally inherited mtDNA variants?
Both Kearns-Sayre syndrome and MELAS
Which cells do nDNA variants of mitochondrial diseases mostly affect?
Cells with high metabolic activity
What are the phenotypes of mitochondrial diseases characterized by?
All of the above
What markers are involved in the clinical diagnosis of genetic diseases of mitochondria?
Phenomic and metabolomic markers
What does genetic testing for mitochondrial diseases focus on?
mtDNA or mtDNA + nDNA
What is the potential treatment focus for genetic diseases of mitochondria?
Slowing disease progression and supportive care
What is the potential use of assisted reproductive technologies for future offspring for mtDNA variants?
Testing of blastocyst for variant and degree of heteroplasmy to select which to implant
What can affect mitochondrial function, including causing organ of Corti hair cell loss and deafness for specific mtDNA variants?
Environmental chemicals, drugs, and antibiotics
What are current clinical trials using nDNA gene transfer for mtDNA genes showing improvement in?
Visual acuity with unilateral injection of the gene-containing virus
What is a potential complication for genetic therapy of mtDNA causing variants?
Inaccessibility by current technologies
What is associated with mitochondrial decline with aging and its potential links to neurological disorders?
Gradual decline in mitochondrial function
What are diet effects associated with in relation to mitochondrial biogenesis?
Obesity and adult-onset diabetes
How many protein-coding genes are present in the mitochondrial genome?
13
What enzyme replicates the mitochondrial genome?
DNA Pol gamma
What is the size of the mitochondrial genome?
16.6 kbp
Which enzyme is involved in transcription of the mitochondrial genome?
POLRMT
What is the main factor leading to a higher rate of spontaneous mutations in the mitochondrial genome?
Higher error rate of DNA Pol gamma
What are the two types of mitochondrial genome?
Homologous and heterozygous
What process did mitochondrial inheritance evolve from?
Phagocytosis of alpha proteobacteria
What does mitochondrial haplotype phylogeny suggest about Eve's mitochondria?
Her peopling of the world started about 200,000 years ago
What is the mutation rate of the mitochondrial genome like in coding regions compared to non-coding regions?
Slower in coding regions
What is crucial for cellular health in relation to mitochondrial genomes?
Mitochondrial function and biogenesis
What can mitochondrial genomes be transmitted through, potentially leading to a mixture of disease and non-disease variants?
3-parent zygotes and in vitro fertilization methods
Study Notes
Understanding the Mitochondrial Genome and Inheritance
- The mitochondrial genome is a circular double-stranded DNA with heavy and light strands, which is called a nucleoid when associated with proteins.
- There can be multiple copies of the mitochondrial genome per mitochondria and multiple mitochondria per cell, with levels varying in different cell types.
- The mitochondrial genome is 16.6 kbp in size and contains 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes, which are involved in mitochondrial protein synthesis.
- The mitochondrial genome is replicated by DNA Pol gamma, which has a higher error rate than nuclear DNA polymerases, leading to a higher rate of spontaneous mutations.
- Transcription of the mitochondrial genome involves nucleus-encoded proteins that are imported into the matrix, with TFAM, TFB2M, and POLRMT forming the active transcription site.
- Mitochondrial genomes can be homologous (all the same) or heterozygous (a mixture), with heteroplasmy potentially leading to variable penetrance and expressivity of disease-causing variants.
- Mitochondrial inheritance evolved from the phagocytosis of alpha proteobacteria and is somewhat similar to bacteria in terms of circular DNA and reproduction by fission.
- Mitochondrial haplotype phylogeny suggests that Eve's mitochondria and her peopling of the world started about 200,000 years ago, with variants developing via DNA replication/repair errors and subsequent selection.
- The mutation rate of the mitochondrial genome is slower in coding regions than non-coding regions, and there is some evidence of recombination with heteroplasmic cells/individuals.
- Most proteobacterial genes were incorporated into the host genome over evolutionary time.
- Mitochondrial genomes can be transmitted through "3-parent" zygotes and in vitro fertilization methods, potentially leading to a mixture of disease and non-disease variants.
- The mitochondrial genome is associated with multifactorial diseases and genetic diseases, with mitochondrial function and biogenesis being crucial for cellular health.
Test your knowledge of the mitochondrial genome and inheritance with this quiz. Explore the structure, replication, transcription, and inheritance patterns of the mitochondrial genome, as well as its role in disease and cellular health.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
