What is the role of inactive MLH1 in the development of some ...

[bobthebuilder]

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]

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.

[bobthebuilder]

TYSM

[jomama]

Excellent