Browsing by Subject "mutaatio"

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  • Saarela, Olli (Helsingfors universitet, 2016)
    The potato virus Y (PVY) is a member of the family Potyvirus, which is the largest plant pathogenic virus family. PVY is one of the most important pathogens of the nightshade family (Solanaceae) plants. PVY is a particular problem in seed potato production, as well as in tomato and pepper production. Some PVY races cause necrotic symptoms (PTNRD) in potato tubers, which will make the tubers unsuitable for use. This thesis studied the ability of several recombinant strains of PVY to infect these three plant species. First objective was to find out which recombinant strains can infect the plants systemically and whether some of them will cause PTNRD symptoms in potato tubers. Secondly, we wanted to find out what parts or even specific amino acids in the HCpro of PVY affect the infection ability of the virus. This was done by comparing the genomes of the recombinant and wild type viruses and based on the experimental data. Finally, we wanted to see if the mutations would persist in the virus genomes for the duration of the infection. The test plants were infected by applying virus contaminated plant juice and grinding powder on the plant leaves. Plants were first grown in growing chambers and then transferred to a greenhouse. The plants were tested for viral infection with DAS-ELISA for three times during different stages of growth. To investigate whether the mutations had persisted in the virus genome, the viral RNA was isolated, multiplied with RT-PCR and then sequenced. Most of the recombinant viruses were not able to systemically infect either of the potato cultivars tested (cv. ‘Nicola’ and cv. ‘Annabelle’). ‘Nicola’ was more susceptible than ‘Annabelle’. The Tyr323Phe-mutation in the HCpro seemed to have a positive effect on the viruses ability to infect ‘Nicola’ in recombinant O5ON-F. PTNRD was caused by recombinants O5NNO45, N605-F and O5ON-F only in ‘Nicola’. Tyr323Phe-mutation had persisted in the N605-F during the infection. Tomato cv. ‘Moneymaker’ was more resistant towards the recombinants than cv. ‘Ildi’, though both cultivars were considerably more susceptible towards the recombinants than either of the potato cultivars or the pepper cultivars. The pepper cultivars tested were resistant towards PVYN605 and PVYOUK.
  • Rämö, Joel (Helsingfors universitet, 2016)
    Familial combined hyperlipidemia (FCH) is a complex and common familial dyslipidemia characterized by elevated total cholesterol and/or triglyceride levels with over five-fold risk of coronary heart disease. The genetic architecture and contribution of rare Mendelian and common variants to FCH susceptibility is unknown. In 53 Finnish FCH families, we genotyped and imputed nine million variants in 715 family members with DNA available. We studied the enrichment of variants previously implicated with monogenic dyslipidemias and/or lipid levels in the general population by comparing allele frequencies between the FCH families and population samples. We also constructed weighted polygenic scores using 212 lipid-associated SNPs and estimated the relative contributions of Mendelian variants and polygenic scores to the risk of FCH in the families. We identified, across the whole allele frequency spectrum, an enrichment of variants known to elevate, and a deficiency of variants known to lower LDL-C and/or TG levels among both probands and affected FCH individuals. The score based on TG associated SNPs was particularly high among affected individuals compared to non-affected family members. Out of 234 affected FCH individuals across the families, seven (3%) carried Mendelian variants and 83 (35%) showed high accumulation of either known LDL-C or TG elevating variants by having either polygenic score over the 90th percentile in the population. The positive predictive value of high score was much higher for affected FCH individuals than for similar sporadic cases in the population. FCH is highly polygenic, supporting the hypothesis that variants across the whole allele frequency spectrum contribute to this complex familial trait. Polygenic SNP panels improve identification of individuals affected with FCH, but their clinical utility remains to be defined.