Flashcards in Unit 7 - Mitochondrial Genetics and Forensic DNA Analysis Deck (15):
where are mitochondrial diseases most serious?
in CNS and muscle
-usually related to tissues where there's a high degree of oxidative phosphorylation activity
-commonly neuropathies, encephalopathies, and myopathies
are mitochondria self sufficient?
no, their full function is linked to nuclear genes
-some processes are governed by mitochondrial genes, others by nuclear genes
-thus, defects in mitochondrial function could be autosomal or X-linked mutations of nuclear genome, or mutations of mitochondrial DNA itself
mitochondria transmitted in egg cytoplasm
-few, if any mitochondria present in pronucleus of sperm
homozygosity for one or more cytoplasmic genes
-usually refers to population of mitochondria that all have same genetic composition
heterozygosity for one or more cytoplasmic genes
-two or more different populations of mitochondria are present in a cell
-heteroplasmy in cytoplasm is analogous heterozygosity in nucleus
how can a mother be heteroplasmic?
mother may be unaffected, but have affected children, or vice versa
-mother must have low frequency of mutated cells, but passes higher frequencies to children who express disease, or vise versa
-require 85% mutant mitochondria in cell for disease to manifest
why are mitochondrial disorders often progressive with late onset? how is this explained?
due to increase, over time, in numbers of mutations per cell and numbers of mutant cells
-replicative segregation in oogenesis (relative proportions of mutant mitochondria can increase or decrease) or acquired mutations (that undergo replicative segregation, but not transmitted to progeny)
what is MERRF?
myoclonic epilepsy with ragged red fiber disease
-mitochondrial disorder that shows bnormally staining mitochondria
what is forensic DNA analysis?
both nuclear and mitochondrial DNA used
-sequence variability with high degree of polymorphism
-nuclear DNA is more robust, for hypervariable minisatellite regions and DNA fingerprinting
what are sources of error for DNA analysis?
quality of specimen
-poor sample collection/preparation
-degradation or contamination
statistical analysis and interpretation
-analyze sufficient number of polymorphisms with high degree of variability
-consider allele frequencies vary between populations
-consider differences in allele frequencies in different racial and ethnic groups
what can mitochondrial DNA analysis be used for?
-siblings carry same mDNA
-link individuals by comparing maternal mitochondrial lineages
-family identity (NOT individual identity)
paternity and medicine
include or exclude putative father based on biological evidence
-minimum of 2 probes
-frequency of alleles in families differ from population frequencies
what is CODIS?
combined DNA information system
-all 50 states, US army, FBI, US Navy, Department of Justice --> all state, local, and federal law enforcement agencies
-enables all crime labs to exchange and compare DNA profiles electronically, to link crimes to each other and to convicted offenders