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.
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.
- 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.
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.
Lac Operon 1
- 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.
Lac Operon 2
- 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 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.
- 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
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)
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