Question

1. Epigenetic effects on gene expression may occur through covalent modifications of ____ and _________.
2. Overexpression of ___________, which bind to and silence mRNAs, may lead to the development of cancer.
3. Precarcinogens are themselves not carcinogens but may be modified in the liver to become a carcinogen by a process known as __________ __________.
4. Nude mice are useful for investigating cancer cells because the nude mice lack a functional _______ system.

Answer 1

1. Epigenetic effects on gene expression may occur through covalent modifications of seqence of DNA and histones of protein.

2. Over expression of CDNA which bind to and silence mRNAs, may lead to the development of cancer .

· over expression of cyclin D occur without amplification are selected in response to a preexisting local cancer-promoting environment

3. Precarcinogens are themselves not carcinogens but may be modified in the liver to become a carcinogen by a process known as carcinogen activation

· The activation of most precarcinogens is carried out by liver proteins that are members of the cytochrome P450 enzyme family. Members of this enzyme family catalyse the oxidation of ingested foreign chemicals, such as drugs and pollutants, to make the molecules less toxic and easier to excrete from the body and oxidation reactions convert foreign chemicals into carcinogens by a phenomenon known as carcinogen activation

4. Nude mice are useful for investigating cancer cells because the nude mice lack a functional Tcells in the immune system

· Absence of thymus means that there is no production of T cells in these mice. Therefore, they are unable to activate the different types of immune responses (adaptive) during the implantation of cancer cells.