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)