L'adn des mitochondriesAEst linéaireBCode sur les deux brins des gènes qui sont sans intronsCCode les ARNt et ARNmDCode toutes les protéines de la mitochondrieEEst transmis par les deux parents

L'adn mitochondrial estATransmis par le père uniquementBConstitué d'exons et d'intronsCCirculaireDConstitué de longues séquences codantesEUne très longue molécule

Mitochondria are thought to have been independent bacterial organisms that were engulfed and integrated into eukaryotic cells approximately two billion years ago.  Most of the mitochondrial genome was lost or transferred into the large central genome of the eukaryotic nucleus, leaving only a residual genome within each mitochondrion.Because each cell contains multiple mitochondria, mitochondrial DNA (mtDNA) mutations may result in a condition known as heteroplasmy, or the intracellular mixture of wild-type mtDNA and mutant mtDNA.  Just as the cellular ratio of wild-type to mutant mtDNA varies, the overall mtDNA content within tissues or organs is also highly variable.  For this reason, disease-causing mutant mtDNA manifests phenotypically only when the majority of mitochondria express the deleterious allele.  In addition, the variability in mtDNA content makes it possible for individuals with the same mitochondrial mutation to display drastically different clinical symptoms.To investigate how heteroplasmy influences disease manifestation, researchers analyzed an A→G substitution at nucleotide 3243 in the tRNAleu gene of mtDNA.  This mutation has been associated with hereditary hearing loss, diabetes mellitus, and a syndrome characterized by mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes.Blood samples were collected from multiple participants, and the region surrounding the A3243G mutation was amplified via PCR.  The PCR products were subsequently treated with the restriction enzyme ApaI and analyzed on a PAGE gel after removal of the enzyme.  The wild-type undigested PCR product is 161 bp in length, but the PCR product amplified from the A3243G mutant is digested into two fragments by ApaI.Figure 1  PAGE visualization of PCR product samples following ApaI digestion.  Double helical DNA of known length was used as a ladder (lane 7).In a followup study, members of a single family, all of whom were confirmed to have the A3243G mutation, were tested using an audiometry examination to assess hearing impairment (Table 1).  The subjects carried no other genetic mutations known to cause hearing loss.Table 1  Audiometry Results from Family Members with the A3243G MutationGenderDegree ofhearing lossAge at test(years)FemaleNone40FemaleModerate54FemaleModerate43MaleSevere32FemaleMild29MaleNone16Adapted from Hadjivasiliou Z, Pomiankowski A, Seymour RM, Lane N. Selection for mitonuclear co-adaptation could favour the evolution of two sexes. Proc Biol Sci. 2012;279(1734):1865-72. Question 34What conclusion can be drawn from the results shown in Figure 1?A.The samples were analyzed under denaturing conditions.B.The samples were analyzed under reducing conditions.C.The samples were analyzed using a native gel.D.The samples were analyzed using a pH gradient throughout the gel.

what is the mitochondria

Where are most of the proteins synthesised in a typical eukaryotic cell?Group of answer choicesGolgiMitochondriaCytoplasm and RERRER

Recall the function of mitochondria.