Genetics: Test 2
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ATP is produced in the respiratory chain by
Mitochondrial defects may cause decreased _____.
- energy production
- Result= "any sign in any tissue or organ at any age"
Mitochondrion contains its own genome.
DNA self-replicates within mitochondria.
Each mitochondria has several copies of mtDNA (5-10)
Each cell has many mitochondria
Mitochondria are abundant in oocyte.
How many mitochondria are found in sperm?
4, located at the neck, typically do not enter the ovum
mtDNA codes for __ genes
- mtDNA = 37 genes
- 2 rRNAs
- 22 tRNAs
- 13 Oxphos polypeptides
What has a higher mutation rate, mtDNA or nuclear DNA?
mtDNA has a mutation rate that is 10x higher than nuclear DNA
Mitochondrial mutations accumulate as we age; therefore, mtDNA mutations are found even in healthy individuals
A cell may have a mixture of normal and mutant mitochondria. This is referred to as?
Heteroplasmy and is due to replicative segregation of mitocondria during mitosis.
Which organs or tissue are the most vulnerable to mitochondrial disorders?
Tissues that have high energy requirements.
Defective OxPhos causes an increase in _______ in mitochondria and the cytoplasm.
Elevated NADH/NAD ratio leads to elevation of ?
Leads to impaired function of?
- elevation of Plasma lactate
- impaired function of TCA
Provocative tests for mitochondrial disorder
- Glucose tolerance test
- Measure CSF lactate, pyruvate if plasma values are normal
- Plasma lactate and pyruvate after exercise
Progressive adult muscle weakness.
Fatal infantile myopathy
How to diagnose a mitochondrial myopathy diagnosis
- Muscle biopsy
- Light microscopy
- Electron microscopy
- Myocloniec Epilepsy
- Ragged Red Fibers
- Generalized muscle weakness
80% of MERRF mutation people have a mtDNA mutation in what gene?
- Mitochondrial Encephalomyopathy
- Lactic Acidosis
- Stroke-Like episodes, recurrent
MERRF have mutation in
MELAS have mutation in
- MERFF= tRNA-lysine gene
- MELAS= tRNA-leucine gene
Kearns-Sayre Syndrome's symptoms are referred to as
- "Opthalmoplegia Plus"
- Ptosis, strabismus, pigmentary retinopathy, hearing deficit, ragged red fiber
8993T>G in the ATP6 gene most common mutation for mitochondria encephalomyopathy _____
Diabetes mellitus shows some evidence of follwing a maternal inheritance pattern. Mutation is in?
Subacute necorizing encepalomyopathy:
Bilateral symmetrical focal regions of necrosis in the thalamus, pons, inferior olives (brain) and spinal cord
Most cases are due to mutations in nuclear genes for ____
Mutations in genes for OxPhos (Complex I, II, IV)
•Skewed X chromosome inactivation can result
in females manifesting signs of X-linked recessive disorders that are typically seen in affected malesExample:girls with Duchenne
muscular dystrophy or with hemophilia A
•Females with Turner syndrome and a 45,X
chromosome constitution also manifest the clinical signs of an X-linked recessive disorder if their single X chromosome carries a mutant allele.
•Females with an X-autosome
translocation have preferential inactivation of their normal X chromosome (to
maintain activity in the autosomal fragment), sometimes resulting in
manifestations of an X-linked recessive disorder.
•The union between an affected father and a
carrier mother can produce a daughter affected with an X-linked disorder;
always consider possible consanguinity/incest.
Atypical X-Linked Effects
EEC Syndrome (AD Inheritance)
- Ectodermal dysplasia
Isolated defects are the presentation of
Familial clustering of a trait with no distinctive Mendelian inheritance pattern.
Recurrence risks are _____, not Mendelian
- Multifactorial Inheritance
Multifactorial inheritance has much higher risk for ____
Recurrence risks increase with the severity of the disorder
- first-degree relatives
- Ex. cleft-lip and palate
Defect in neural groove closure prior to __ days
- Neural tube defects (developmental pathogenesis)
- Defect in neural groove closure prior to 28 days
Neural Tube: Anterior closure defect
Neural Tube Defects: Cervical and upper thoracic defect
Neural Tube Defects: Mid-to-caudal neural groove defect
Myotonic Dystrophy is a repeat expansion mutation of
- CTG (5-35 repeats)
- Muscle weakness and wasting, facial wekaness, voluntary and percussion myotonia
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