Geneettisen rappeutumisen mekanismeja

Tässä listaa rappeutumisen mekanismeista ja tieteellistä tutkimusaineistoa niihin liittyen.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6541967/
"Many studies have reported that CpG-SNPs are associated with different diseases, such as type 2 diabetes, breast cancer,

coronary heart disease, and psychosis which show a clear interaction between genetic (SNPs) and epigenetic (DNA methylation) regulation."


https://www.nature.com/articles/modpathol2009130
"Loss of expression of the O6-methylguanine DNA methyltransferase (MGMT) protein is a frequent occurrence in many types of cancer, including 30–46% of sporadic colorectal cancers.9, 10, 11, 12, 13 This is almost invariably associated with methylation of the MGMT promoter.9 MGMT is a ubiquitously expressed DNA repair protein that protects against mutagenesis by repairing mutagenic O6-methylguanines within DNA. By direct cleavage of the methyl adducts, the enzyme can restore the affected guanine
nucleotides to normal.14 If this fails to occur, O6-methylguanines can pair erroneously with thymine during DNA replication, resulting in G:C>A:T transitions in the DNA, which can be important in neoplastic transformation."
"Recently, MGMT methylation was found to be closely associated with the C>T SNP (rs16906252) within the first exon of MGMT in colorectal cancer."


https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004585
"Surprisingly, hydroxymethylated sites are consistently associated with elevated C to G transversion rates at the level of segregating polymorphisms, fixed substitutions, and somatic mutations in tumors."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5578878/
"DNA hypomethylation promotes genomic instability 4, in many cases leading to an increased mutational load and activation of proto-oncogenes."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4930698/
"DNA methylation has been linked to mismatch repair (MMR) deficiency and genomic instability in multiple contexts, in both cell lines and in disease. In the HCT116 colorectal cancer cell line, ablation of catalytically active DNMT1 causes cell cycle arrest and apoptosis due to increased chromosomal instability. In mouse ES cells, loss of Dnmt1 also causes global hypomethylation and increased mutation rates."

https://www.ncbi.nlm.nih.gov/pubmed/20846930
"If we assume that CpHpG methylation also occurs in the germline, and that 5mC deamination can occur within a CpHpG context, then we might surmise that methylated CpHpG sites could also constitute mutation hotspots causing human genetic disease. To testthis postulate, 54,625 missense and nonsense mutations from 2,113 genes causing inherited disease were retrieved from the Human Gene Mutation Database (http://www.hgmd.org). Some 18.2 per cent of these pathological lesions were found to be C → T and G → A
transitions located in CpG dinucleotides (compatible with a model of methylation-mediated deamination of 5mC), an approximately
ten-fold higher proportion than would have been expected by chance alone."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC33658/
"Altered DNA methylation and genome instability: A new pathway to cancer?"

http://www.biochemist.org/bio/03905/0012/039050012.pdf
"This increased genome instability is characterized by increased occurrences of mutations, cells with incorrect chromosome number, loss of heterochromatin and mistakes in transcription."

https://www.intechopen.com/online-first/a-hypothesis-to-explain-how-the-dna-of-elderly-people-is-prone-to-damage-genome-wide-hypomethylation
"A reduction in DNA methylation leads to genomic instability, accumulation of endogenous DNA damage, and sensitivity to DNA-damaging agents."

https://jcs.biologists.org/content/112/24/4513
"CpG methylation reduces genomic instability."

https://pdfs.semanticscholar.org/d685/909cc287511ce7ab88368a72de1f09e988b8.pdf
"As well, DNA methylation is thought to be a major contributor of point mutations leading to human genetic disease, when it precedes deamination of 5-methylcytosine (m5C) present within CpG dinucleotides. CpG dinucleotides are hypothesized to be a hotspot for mutations in a variety of genes, where a substantial proportion of intragenic single base-pair mutations (35%) occur in CpG dinucleotides and are the result of C>T or G>A transitions. Consequently, the rate of transitions at CpGs is suggested to be 20-fold higher than transitions at non-CpG sites."

https://www.atdbio.com/content/56/Epigenetics#Role-of-base-flipping-in-DNA-methylation
"When cytosine is mutated to uracil by spontaneous deamination, the DNA glycosylase enzyme UDG (uracil DNA glycosylase) reverses the damage, in a base excision repair mechanism. When the equivalent deamination reaction occurs on 5-methylcytosine, however, the product, thymine, is not repaired by DNA repair enzymes."

ja lista jatkuu....

https://jb.asm.org/content/200/24/e00371-18
"I show that sites methylated by the Dcm enzyme exhibit an 8-fold increase in mutation rate in natural bacterial populations. I also show that modifications at other sites in various bacteria also increase the mutation rate, in some cases by a factor of forty or more."

https://www.cell-stress.com/researcharticles/epigenetic-mechanisms-behind-cellular-sensitivity-to-dna-damage/
"The architecture of the chromatin itself and its level of condensation can greatly impact the expression of genes as well as the sensitivity of the DNA to damage."

"For example, DNA is more highly methylated, and therefore compacted, in areas that contain repetitive sequences to prevent the expression of non-coding DNA, induction of double-stranded breaks (DSBs), transposable elements and inappropriate recombination events likely to occur at repetitive DNA sequences. These events can lead to mutations, genome instability and cancer development."


https://www.labroots.com/trending/cell-and-molecular-biology/13307/warning-using-epigenetic-modifiers-therapeutic-targets
"When chromatin is more 'open,' major genetic disruption is more likely. And when the researchers inhibited an epigenetic modifier called G9a, they found that chromatin accessibility, or openness, increased substantially."

Ensimmäinen ei auennut, ja toinen puhui spontaanisti kehittyvästä syövästä. Luin jutun lähes puoliväliin, eikä siinä vaiheessa ollut sanaakaan genimin rappeutumisesta. Voitko laittaa lainauksen kohdasta, jossa rappeutuminen on mainittu. Juttu on melkoisen pitkä ja Gish Gallop tyyliin linkitit pitkän listan linkkejä.
Oletatko, että joku viitsii käydä ne kaikki läpi ja pyyhkiä taas kerran pöytää väitteilläsi?

Tarjoat syöpää esimerkiksi genomin rappeutumisesta. Farao Hatšepsut sairasti syöpää ja eli vajaa tuhat vuotta Nooan jälkeen. Miten hänen genominsa oli ehtinyt rappeutua? Hänenhän olisi pitänyt omata lähes rappeutumaton genomi, jos sinun väitteesi ihmisten nopeasta geneettisestä rappeutumisesta olisi totta.

ROT lainaa tekstejä genettisistä sairauksista, joita on ollut varmasti yhtä kauan kuin ihmisiäkin ja väittää, että genomi rappeutuu. Yhdessäkään lukuisista läpi käymistäni lainauksista ei viiata siihen, että genenomin virheet olisivat oleellisesti lisääntyneet. Genomin rappeutumisesta en löytänyt sanaakaan.

Eli taas kerran ROT:n ihan ikiomaa tulkitaa. Noloa RPT noloa.

Mietitkö usein kysymystä, oliko Amerikkaa olemassa ennenkuin Kolumbus "löysi" sen ?

Eli käytät nyt keppihevosena tutkimuksia sairauksista?
Vähän sama kuin menisi poliisiasemalle tutkimaan rikoksia ja toteaisi kaikkien olevan rikollisia.

Jos kysyisit noilta tutkijoilta onko evoluutio totta niin saisit ihan varmasti myönteisen vastauksen. En meinaan löytänyt viitteitä rappeutumiseen vaan ihan normaalia muutosta joka voi olla haitallista, neutraalia tai hyödyllistä. En löytänyt oikean tarkennusta onko kyseessä edes pelkästään haitallisia, vai voiko kyseessä olla jotenkin myös hyödyllinen piirre. Jos väität näiden olevan jotenkin vasta ilmaantunut ihmiselle, niin olet pihalla asiasta. Aikaisemmin olen havainnut sinulta sellaisiakin väitteitä.
Mikä estää hyödyllisen mutaatioiden syntymisen? Missä noissa artikkeleissa väitetään informaatiota hävinneeksi. (Tämähän oli aikoinaan sinulla se pointti).

Ainakin tuo biochemist.org jonka luin (kiinnostavaa, kiitos!) valotti koko artikkelin pituudella sitä asiaa, että epigenetiikan yksi tärkein tehtävä on suojata genomia ("Decades of research have revealed that these epigenetic mechanisms play important roles in helping to maintain genome integrity"), minkä se tekee kolmella eri tavalla. Eli se nimenomaan suojaa häiriötekijöiltä.
Vasta ikääntyessä suoja alkaa pettää, eikä tähän mennessä ole selvää, aiheuttaako vanhenemisen prosessi heikentynyttä epigeneettistä suojaa vai päinvastoin. Eli lainaamasi heikentävä tekijä - sitaatti oli aivan artikkelin jossain lopulla ja koski vanhenemista.