Illustrations for “Reading Between the Genes”
May 13 2011
ILLUSTRATIONS FOR AZEEN GHORAYSHI’S BERKELEY SCIENCE REVIEW COVER STORY ON SCIENTISTS’ EFFORTS TO MAP THE DARK GENOME. (CAPTIONS BY AZEEN GHORAYSHI)
To fit inside each individual cell, DNA must be condensed and packaged into fibers called chromatin. The double-stranded helical DNA first wraps around clusters of proteins called histones. The histones are arranged along the DNA like beads on a string, allowing the histone-DNA spool to coil, fold, and loop around themselves. The final product is the tightly packed fiber of chromatin, organized into distinct sets of chromosomes.
Histone modifications are one of many cellular mechanisms that work to control gene expression. Processing long amino acid tails (yellow), histones can be “tagged” with chemical modifications (red). These tags are then recognized by other cellular machinery that can work to silence or activate the DNA in that region. Histone modifications are a type of epigenetic mechanism, meaning they are heritable but not encoded directly in the genome.
Drosophilia melanogaster.
Caenorhabditis elegans.
In alternative splicing, a single gene can be read in multiple ways to produce different proteins. After transcription occurs (step 1), distinct segments of the RNA called introns (gray) are removed by cuts made on both sides at locations called splice junctions. The remaining RNA (colored) can then be reconnected to form different strands of mRNA (step 2). The different mRNAs will then serve as templates for the synthesis of different proteins (step 3).
