Mitochondrial inheritance Flashcards
(18 cards)
What is a sex-limited trait?
A trait that occurs in only one of the sexes due to anatomical differences
Examples include inherited uterine or testicular defects.
What is a sex-influenced trait?
A trait that occurs in both sexes but is more common in one sex, such as male-pattern baldness
Male-pattern baldness is influenced by sex differences in hormone levels.
Is male-pattern baldness strictly X-linked?
No, it is not strictly X-linked; autosomal genes also influence it
Variation in the X-linked androgen receptor gene is associated with baldness.
What is mitochondrial inheritance?
Inheritance of traits through mitochondrial DNA, which is maternally inherited
Mitochondrial DNA has a unique mode of inheritance and phenotypic variability.
What is the mutation rate of mitochondrial DNA compared to nuclear DNA?
About 10 times higher
This higher rate is due to a lack of DNA repair mechanisms and damage from free radicals.
What is heteroplasmy?
The presence of both mutant and normal mtDNA within a single cell
Heteroplasmy contributes to variable expression in mitochondrial diseases.
What type of inheritance pattern is seen with X-linked dominant traits?
Vertical transmission; disease phenotype seen in generation after generation
This pattern contrasts with X-linked recessive traits, which may skip generations.
What is the expected recurrence risk for a heterozygous female mating with a normal male for X-linked dominant traits?
50% of sons affected; 50% of daughters affected
What is the expected recurrence risk for an affected male mating with a normal female for X-linked recessive traits?
0% of sons affected; 100% of daughters are heterozygous carriers
What is the primary function of mitochondria?
To produce adenosine triphosphate (ATP), the energy source essential for cellular metabolism
What is Leber hereditary optic neuropathy (LHON)?
An mtDNA disease characterized by rapid loss of vision in the central visual field due to optic nerve death
LHON affects about 1 in 10,000 persons and typically begins in the third decade of life.
What are the symptoms of myoclonic epilepsy with ragged-red fibers syndrome (MERRF)?
Epilepsy, dementia, ataxia, and myopathy
MERRF is characterized by heteroplasmic mtDNA and highly variable expression.
What type of mutations can cause mitochondrial diseases?
Single-base mutations, duplications, and deletions
Examples include MERRF, MELAS, Kearns–Sayre disease, and Pearson syndrome.
What is the prevalence of mitochondrial diseases in the population?
Approximately 1 in 4000 individuals
Most are due to mitochondrial mutations, with a smaller number caused by nuclear mutations.
True or False: Mitochondrial DNA is inherited paternally.
False
Mitochondrial DNA is exclusively inherited through the maternal line.
What organ systems are most affected by mitochondrial diseases?
Organ systems with large ATP requirements and high thresholds
The central nervous system is particularly affected as it consumes about 20% of the body’s ATP production.
What is a common mutation associated with late-onset deafness?
A mitochondrial mutation
What is the relationship between mtDNA mutations and aging?
Accumulation of mtDNA mutations may contribute to the aging process
This is thought to be due to free radical formation over an individual’s lifetime.
