Gene Expression. Supplementary reading: Chapter 19 in Campbell 7 th edition. Background. Genes serves as a recipe for building a protein molecule (these are called “structural genes”).
Supplementary reading: Chapter 19 in Campbell 7th edition
Genes serves as a recipe for building a protein molecule (these are called “structural genes”)
When a particular protein is needed by the cell, the corresponding gene, made of DNA, is turned "on," or transcribed into messenger RNA, which then carries the "protein recipe" to the protein-making machinery of the cell (ribosomes) where it is translated into a protein product.
Chromosome structure: chromatin (DNA helices) are wrapped around a central histone protein core. "nucleosomes": DNA wrapped around histones (proteins); forms beadlike loops in the chromatin.
"euchromatin": uncoiled DNA that is being transcribed
"heterochromatin": tightly coiled DNA; contains inactive genes
Pre-RNA (initial transcript) contains useful information (from exons) - coding for protein- interspersed with some “extra“ noncoding (intron) sequences. It must be modified before the ribosome can make the protein it calls for.
mRNA Cleavage : “spliceosomes” cut and splice only the necessary info together, before it reaches the ribosome for translation.
“Modification of mRNA : prokaryotes -vs- eukaryotes”http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html#short movie of mRNA editing (introns/exons)
Deuterostomes or Protostomes
Very well-studied in fruit flies (located on the 3rd chromosome)
"Antennapedia" is a hox gene first discovered in Drosophila which controls the placement of legs. Scientists can induce mutation in this, causing legs to grow in the place where antennae are normally found (left photo)
Also can manipulate the pbx (post-bithorax) and bx (bithorax) genes to this effect (right photo)