Review Question - QID 4525

Epigenetic changes are defined as inheritable genetic alterations that do not involve DNA mutation.

The cells in a multicellular organism have almost identical DNA sequences, yet maintain different terminal phenotypes. This nongenetic cellular memory, which records developmental and environmental cues is the basis for epigenetics. DNA methylation, histone modification, nucleosome location, or noncoding RNA are hypothesized to contribute to the process.

Maher et al discuss epigenetic influences in the realm of orthopaedics. They report new data stating that increases in matrix metalloproteinase (MMP) expression in osteoarthritis is associated with altered methylation of key promoter sequences. They also report elevated levels of an enzyme involved in epigenetic gene silencing in osteoarthritis-affected chondrocytes, SIRT1, increased the expression of matrix genes and suppressed that of MMPs.

Incorrect Answers:
Answer 1: Transgenes are genes that are artificially introduced into a single-celled embryo and are present in all cells of that organism.
Answer 3: Gene enhancers are a region of a gene that positively regulates rates of transcription.
Answer 4: Gene promoters are a regulatory segment of DNA that controls start of transcription adjacent to the transcription initiation site of a gene.
Answer 5: Transformation refers to inserting a plasmid into a bacterium with added recombinant DNA.