You are studying the changes that have occurred in the genomes of members of a family susceptible to an inherited form of liver cancer. You find that afflicted family members harbor a mutation in the zinc-finger motif of a cell-cycle regulatory gene. Which of the following is the most likely result of this mutation?
A) decreased binding of a transcription factor to a DNA sequence
B) enhanced binding of hormones to receptors
C) enhanced transport of a hormone receptor complex into the nucleus
D) stimulation of mRNA synthesis
E) "unzipping" of leucine-rich helices

Question

Quizplus · Accepted Answer

The zinc-finger motif is a structural motif that interacts with DNA. A mutation in this motif would likely affect the binding of a transcription factor to a DNA sequence, leading to decreased binding. The zinc finger domain is a DNAbinding motif consisting of specific spacings of cysteine and histidine residues that allow the protein to bind zinc atoms. The metal atom coordinates the sequences around the cysteine and histidine residues into a fingerlike domain. The finger domains can interdigitate into the major groove of the DNA helix. The spacing of the zinc finger domain in this class of transcription factor coincides with a half turn of the double helix.

You Are Studying the Changes That Have Occurred in the Genomes