Author Question: What is the role of inactive MLH1 in the development of some forms of inherited colon cancer? a. ... (Read 76 times)

bobthebuilder · **on:** Jun 25, 2018

What is the role of inactive MLH1 in the development of some forms of inherited colon cancer?

a. Deletion of a nucleotide repeat in the DUX4 gene.
b. DNA damage is left unrepaired.
c. Expansion in the number of cyto-sine-guanine (CG) dinucleotide.
d. Abnormalities of chromosome 11p15.5 that lead to downregulation of IGF2.

Question 2

Housekeeping genes are vital to the function and maintenance of all the body's cells. What char-acteristic is associated with these genes?

a. They lack encoding histones.
b. They are transcriptionally active.
c. Ribosomal RNA genes are absent.
d. Epigenetic silencing has occurred.

nyrave · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

ANS: B
A major cause of one form of inherited colon cancer (hereditary nonpolyposis colorectal cancer HNPCC) is the methylation of the promoter region of a gene, MLH1, whose protein product repairs damaged DNA. When MLH1 becomes inactive, DNA damage accumulates, eventually resulting in colon tumors. Facioscapulohumeral muscular dystrophy (FSHMD) is associated with the DUX4 gene. Fragile X is associated with the cytosine-guanine (CG) dinucleotide. Downreg-ulation of IGF2 is associated with Russell-Silver syndrome.

Answer to Question 2

ANS: B
A small percentage of genes, termed housekeeping genes, are necessary for the function and maintenance of all cells. These genes escape epigenetic silencing and remain transcriptionally ac-tive in all or nearly all cells. Housekeeping genes include encoding histones, DNA and RNA polymerases, and ribosomal RNA genes.