Molekularbiologie (Fach) / Kart (Lektion)
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- how is the X chromsome inactivated in mammals? Through silencing DNA is heavily methylated and histones are modified as in heterochromatin
- Position effect varigation. · example of an epigenetic effect · gene activity is affected by imprinting (controls expression of genes from mother and father), some genes the copy from mother is sileneced, in the other from the father. No gene expression, when one is silenced and the other absent! · Verlagerung von Genen vom euchromatischen zum heterochromatischen Bereichàstilllegung · Drosophila: Normalerweise wird das white gen expremiert, welches zu einem Phänotyp mit roten Augen führt. · Das white gen wird in den Heterochromatin verlagert und stillgelegt, Folge ist, dass die Augenfarbe ein rot-weißes Mosaik ergibt.
- How are transposons keept quiet by the host? Through silencing. DNA Methylation required to silence transposons.
- What happens to plants that can no longer methylate DNA? Transposons get reactivated, and subsequently the plants get less and less fit.
- Explain paramutation using one example? Paramutation: The interaction of two alleles of the same locus resulting in a heritable change of one allele that is induced by the other allele. The maize b1 locus has a paramutagenic allele. o Plants with an active B-1 allele have a lot of purple anthocyanin pigmentation. o The B' allele is weakly active, and plants are pale. o The B´allele is heavily methylathed. o It should be purple, because the B1 is dominant. o Instead, the B' allele paramutates B-1 to B', and the plant is pale.
- 27. What are point/region/holocentric centromers? Basically this defines the centromer sites, point centromers are very small, regoin centromers hundreds of kilobases, in holocentric centromers there is no defined region (whole chromosome)
- What is the role of telomerase? it solved the "end" problem by prolonging special structures "telomeres" at chromosome ends. lomerase is a special DNA polymerase that has a protein and RNA component The RNA has a short template that specifies the sequence of the telomere repeat to be added. The protein synthesizes the telomeric DNA using the RNA as a template