paper 2

• what are structural genes?


  genes that code for a protein that has a function in a cell
• what are regulatory genes?

  genes that code for proteins that control the expression of another gene
• what are the two genes involved in transcriptional control?

  regulatory gene and structural gene
• what does a promoter do?

  a DNA sequence that enables the transcription of structural genes and is the binding site for RNA polymerase
• what is an operon?

  a cluster of structural genes that is under the control of one promoter
• give two features of the lac operon.

  it's found in bacteria and contains genes needed to digest lactose
• Operons are far more common in prokaryotes than eukaryotes. Suggest why.

  Prokaryotes are much smaller organisms that have smaller genomes than eukaryotes. They are made up of one cell that only needs to respond to changes in its environment.

  In contrast, most eukaryotes are made up of many cells, forming tissues and organs. Coordination between many cells requires a more complex transcription control than operons can provide.
• Homeobox genes are highly conserved between most animal species. Suggest why.

  Mutations in homeobox genes, which alter the body plan, are likely to be lethal. As a result, mutations in homeobox genes are likely to be selected against during evolution.
• the homeobox codes for the transcription factor's homeodomain
• what is the homeodomain?

  DNA-binding site found in transcription factors.
• what is allopatric speciation?

  Geographic isolation leading to the formation of new species.
• what is sympatric speciation?


  Speciation occurring within a population without geographic isolation.