Gene regulation

• what are genes that code for enzymes that are constantly required in the metabolic pathway called

  Housekeeping genes
• What are genes that code for protein based hormones that are only required at certain times called

  Tissue specific genes
• Where is the genome present

  The entire genome is present in every cell, including genes that are not required by the cell
• Why is expressing genes only when needed efficient

  It prevents products from being wasted
• What is translational control

  Degradation of mRNA- more resistant molecukes last longer in the cytoplasm

  binding of inhibitory protein to mRNA to stop binding to ribosome

  protein kinase
• What is protein kinase

  Enzymes which catalyse the addition of phosphates to proteins which changes the tertiary structure as well as the function of the protein
• Why does DNA have to be wrapped around histones

  To pack it into the nucleus
• What are transcriptional factors

  Chromatin remodelling and histone modification
• What is the DNA and histone complex called

  A chromatin
• What is heterochromatin

  Tightly wound DNA around his tine causing it to be visible in cell division
• What is euchromatin

  Loosely wrapped DNA during interphase
• why can transcription not happen if the DNA is wrapped tightly around the histone

  Because RNA polymerase cannot access the genes
• What does protein synthesis occur


  In interphase
• Why does DNA coil around histones

  Because histones are positively charged and histones are negatively charged
• what happens to the histone if a acetyl group or a phosphate group are added

  It reduces the histones charge so the DNA coils less tightly
• What happens to the histone if a methyl group is added

  Makes the histones more hydrophobic so they bind more tightly causing DNA to coil more tightly
• What is an operon


  a group of gene under the controls of th same regulatory mechanisms so expressed at the same time
• What organism are operons more common

  Prokaryotes
• What is the lac operon


  A group of 3 genes lac z, lac Y and lac A involved in the metabolism of lactose
• what do the genes in a lac operon code for

  B-galactosidase lactose permanent and transacetylase
• What is the regulatory gene in the lac operon

  lac I and codes for the repressor proteins
• What does the repressor protein do

  Prevents the transcription of the structural genes in the absence of lactose
• Where does the repressor protein bind

  Operator
• What happens in the lac operon when lactose is present 


  Lactose binds to the repressor protein causing it to change shape so it can no longer bind to the operator. So RNA polymerase can now mind to the promoter and transcribe the lac genes
• What is the role of cyclic AMP

  cAMP (secondary messenger) binds to cAMP receptor protein so speed up transcription
• What is RNA processing

  The product of transcription is modified. A cap (modified nucleotide) is added to 5 end and tail of adenine nucleotides added to the 3 end.
• What is post translational control

  Involves modifying proteins that have been synthesised including: addition of non protein group, folding or shortening if probing and modifying by cAMP