f215 cellular control

translation, mutations, lac operon, genes, apoptosis, meiosis, genetic diagrams, gene loci, variation, selection

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First stage of protein synthesis.

  • Gene unwinds and unzips, hydrogen bonds between the bases break.
  • RNA nucleotides bind to exposed bases with hydrogen bonds, onto the templete strand.
  • Two phosphates are released, releasing energy for the bonding between nuleotides. 
  • mRNA produced is complemtary to to the templete strand of DNA, copy of base sequence on coding strand of DNA.
  • mRNA released from DNA and out of nucleus through nuclear envolpe.  
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Translation 1

Second stage of protein synthesis, amino acids assembled into polypeptides. 

Condon (three base pairs)

Ribosome - Made from rRMA, two subunits and a groove for mRNA to fit. Reads and assembles. 

Sequence of amino acids 

  • Forms primary structure.
  • Determines tertiary structure- which allows protein to fuction. 
  • If altered the protein can no longer funtion. 

tRNA - Made in nucleus and passes into cytoplasm.

  • Fold into hairpin shapes
  • three exposed bases, at one and particular amino acids can bind. 
  • Other end three unpaired nucleotide bases (anticondon) can temporarily bind with complementary condon.
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Translation 2

Polypeptide assembling 

  • mRNA binds to ribosome, mRNA AUG is exposed and through ATP and an enzyme a tRNA anticondon UAC forms a hydrogen bond.
  • Second tRNA amino acid binds to the second exposed completary condon.
  • Peptide bond forms between two adjacent amino acids, catalysed by a enzyme. 
  • Ribosome moves along mRNA, third tRNA bought and peptide forms between amino acid and dipeptide. 
  • first tRNA leaves to go and collect more amino acids.
  • Polypeptide chain grows until stop condon reached. 


  • DNA is not inside  nucleus, translation begins as soon as mRNA is made.
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Mutations 1

Mutation - random change to genetic material ( base deletion, addition, substitution or triplet repeat) 

Point mutation - One base pair replaces another (substitution)

Insertion/deletion mutations - one or more nucleotide pairs inserted or delectedd (frame shift) 

Genetic Code - genetic disease

  • Deletion of an amino acids causes 70% of sickle cell anaemia cases. 
  • Growth-promoting genes can be changed by point of mutation, remaining permanently switch on, cell division leads to a tumor. 
  • Huntington disease results from expanded triple nucleotide repeat., symptoms manifest later on in life. 
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Lac Operon 1

Enzyme induction

  • when first placed in medium of lactose E.Coli cannot metabolis it. 
  • Only tiny amount of enzymes needed. 
  • B galactosidase - catayses hydrolysis of lactose to glucose to galactose. 
  • Lactose Permease - transports lactose into cell. 
  • Lactose is an inducer as it begins the production of these enzymes. 

Regulator gene - not part of the Operon and distant from it. 

Operator region - O - length of DNA next to structural gene, turns them on and off.

Promoter region - P - length of DNA RNA binds to begin transcription of structural genes Z and Y 

Structural genes - Z - codes for Beta galactosidase 

                           - Y - codes for lactose  premase 

Each consists of base pairs that can be transcibed into mRNA.

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Lac Operon 2

Lactose absent 

  • Regulator gene expressed, and repressor protein synthesised. Two binding sites, one to lactose and one to operator region. 
  • Binds to operator region, covering the promoter region. 
  • RNA cannot bind to the promoter region so structural genes not transcribed. 
  • Enzymes cannot be synthesised. 

Lactose present 

  • Lactose binds to repressor protein. Causes the protein to change shape so it cannot bind to operator region. The promoter region is unblocked. 
  • RNA binds to it and initiates transcription of mRNA genes Z and Y 
  • Enzymes are produced needed to break down lactose for energy. 
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Gene Therapy


  • Functioning Allele is introduced to target cell. Technique needed to get gene to specific location. Specific cell must be removed treated and replaced.
  • Treatment is short lived and repeated regulatory. Specialised cells will not divide and pass on allele.
  • Difficulties in getting allele into genome in functioning state. Host may become immune on next treat,emt to modified viruses.
  • Genetic manipulation restricted to one patient.


  • Functioning alleles of gene is introduced into germline cell- striaghtforward
  • All celss deived from germline cells which contain copy of allele, offspring may also carry and considered unethical.
  • Unknow if introduced allele may have unintentional changes or damage embryo
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Nervous system

Central nervous system - Brain and spinal cord, made up of non-myleinated nerve cells and myelinated axons and dendrons.

Peripheral nervous system - Neurons that carry impluses into and out of the CNS.

  • Sensory - Carry impluses from receptors to CNS
  • Motor - Carry impluses from CNS to effectors
    • Somatic - impluses from CNS to skeletal muscles (conscious control)
    • Autonomic - impluses from CNS to cardiac muscles, smooth muscles in gut wall and glands (non-voluntary)
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Automatic nervous system

  • Controls homeostatic mechanisms ( internal enviroment) and heightened responses with stress response


  • Most active in sleep/relaxation
  • Neurons linked at ganglion with target tissue, long pre-ganglonic neurons
  • Post-ganglionic neurons secret acetylcholine as neuronransmitter.
  • Decrease heart rate, pupil cinstriction, decreased ventilation rate.


  • Active in times of stress
  • Linked at gaglion outside spinal cord, short pre-glanglonic neurons
  • Secrete noradrenaline at synapes
  • increased heart ratel, pupil dilation increased nentilation rate
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Meiosis 1

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