Ch. 16 - Gene regulation in eukaryotes
what two areas of the X chromosome play a key role in X inactivation?
Tsix Xist
first step of X inactivation occurs when X chromosomes pair briefly beginning at the
Tsix gene
in mammals, females (XX) and males (XY) express genes on the X chromosome at the same levels because of
X chromosome inactivation
a change in the DNA sequence of the enzyme histone methyltransferase has been observed in renal and breast cancers. these cells are likely to have
a reduction in methyl groups on histones
Trithorax group (TrxG) complexes epigenetically influence development by
activating various genes
epigenetic changes due to the actions of PcG complexes
are maintained in subsequent cell divisions
how do chemicals found in cigarette smoke induce cancer?
by mutating genes by causing epigenetic changes by changing DNA methylation patterns
a genetic disease in which cells divide uncontrollably is
cancer
examples of epigenetics (4)
chromatin remodeling DNA methylation Localization of histone variants Covalent histone modification
the methylation of a previously unmethylated site is called
de novo methylation
the inactivation of an X chromosome is what kind of event?
epigenetic event
what term explains the variation of gene expression that is not related to the variation of the DNA, is transmissible and is reversible?
epimutation
what is true of X inactivation?
expression of Tsix from both X chromosomes inhibits the expression of Xist in very early embryos, both X chromosomes are active when the Xist gene is inactive the X chromosome is active
smoking of cigarettes induces the formation of lung cancer only by causing genetic mutations in tumor suppressor genes (TRUE OR FALSE)
false
which proteins represent histone modifying enzymes that have been associated with epigenetic changes in cancer cells?
histone acetyltransferase histone methyltransferase histone kinase
DNA methylation of CpG islands, covalent histone modification and chromatin remodeling all may induce cancer by
increasing the expression of oncogenes decreasing the expression of tumor suppressor genes
polycomb group (PcG) complexes epigenetically influence development by
inhibiting various genes
What promotes cancer by increasing transcription of genes that regulate cell cycling?
oncogenes
trans-epigenetic mechanisms are more commonly found in
prokaryotes (bacteria) & single-celled eukaryotes
environmental factors that promote epigenetic changes
temperature toxins diet
are epigenetic changes potential drug targets for cancer treatment?
yes, b/c oncogenes and tumor suppressors can be regulated epigenetically
genomic imprinting and x-chromosome inactivation are examples of
cis-epigenetic mechanisms that occur during development
mutations in chromatin-modifying proteins may contribute to cancer by causing
closed chromatin to inhibit expression of tumor suppressors open chromatin to overexpress oncogenes
genes that are expressed but do not encode polypeptides are *** RNAs
non-coding (ncRNAs)
