F215 notes

CARRIER BOUND:

• Enzyme molecules mixed with carrier e.g. clay, activated glass minerals or gold - binds to carrier by hydrophobic interactions and ionic links 
• Weak bonding forces - detachment (leakage
• Active site isnt altered and easily accessible - fast reaction rate 

CROSS LINKAGE:

• Enzymes covalently bind to a support - cellulose or collagen 
• Enzymes covalently linked to insoluble material using cross linking agent 
• Doesnt immobilise large amount of enzyme 
• Strong covalents bond - little leakage 

ENTRAPMENT:

• Trapped in gel bead/network of cellulose fibres in natural state (inclusion)
• Or physically separated from mixture by semi-permeable membrane - substrate molecules pass through (microcapsule)
• Reaction rates reduced - harder to access active site 
• Found in glucose test strps 
• Active site may be orientated away from substrate 

NUCLEAR TRANSFER

• Donor cells - differentiated somatic cells e.g. taken from udder 
• Cultured on low nutrient medium = stop dividing, dormant - undifferentiate 
• Ovum taken from another animal - nucleus removed = enucleate ovum 
• Donor cell + enucleate ovum placed next to each other - electric pulse causes them to fuse 
• 2nd electric pulse = cell divsion 
• Placed in tied oviduct in sheep - develop as embryo and then be removed 
• Embryo placed in surrogate mother's uterus 
• CLONES OF PARENT AND EACH OTHER 

EMBRYO SPLITTING

• Ovum's collected from high value female e.g. high milk yield 
• Sperm cells taken from high value male - test progeny
• IVF occurs using collected egg and sperm - cell is grown in vitro until a 16 cell embryo 
• Embryo is split into several separate segments - implanted into surrogates 
• CLONES OF EACH OTHER BUT NOT PARENTS 

CO-DOMINANCE:

• 2 alleles of the same gene
• Both are expressed in the phenotype of a heterozygote
• Examples are human blood groups and roan cattle 

AUTOSOMAL LINKAGE:

• Genes for different characteristics 
• Present at different loci but on the same chromosome 
• Linked - often inherited together as dont segregate independently in meiosis
• Reduces number of phenotypes from a cross 
• Example is red eyed and brown coated

DISCONTINUOUS VARIATION

• Qualitative differences between phenotypes
• Fall into clear categories 
• Gender, blood type
• Different alleles at single gene locus = large effect on phenotype 
• Co-dominance, dominance and recessive 

CONTINUOUS VARIATION

• Quantitative differences between phenotypes 
• No distinct categories - wide range of variation 
• Height, weight, yield
• Traits controlled by 2 or more genes - different alleles at each gene locus = small effect on phenotype 

• Random fluctuations in the number of different alleles in a population 
• There is changes in allele frequency 
• Occurs in small populations 
• Variants of alleles can disappear completely and reduce the genetic variation of the population 
• Reduced gene pool

• Genome is mapped 
• Mechanically cut into smaller sections of around 100,000 base pairs 
• Restriction enzymes are used to cut the DNA into smaller fragments 
• Different restriction enzymes are used to different fragment types 
• Fragments are separated in terms of size using gel electrophoresis 
• PCR is used to make many copies 
• Involves addition of free nucleotides - double oxidised and labelled with fluorescent marker 
• Each base has a different colour
• If modified nucleotide is added to the DNA DNA polymerase stops 
• Means all fragments end on a labelled marker 
• Electrophoresis is used 
• Strands are run through a machine - laser reads the colour sequence 
• Sequence of colours = sequence of bases 

• Double stranded DNA sample mixed with supply of free nucleotides and DNA polymerase 
• Heated to 95 = breaks hydrogen bonds to give single stranded DNA 
• Primers added - short lengths of single stranded DNA (10-20 bases long)
• Temperature reduced to 55 - primers anneal and form small sections of double stranded DNA at either end of sample 
• DNA polymerase binds to double stranded sections 
• Temperature increased to 72 degrees (optimum for Taq) - extends primers by adding free nucleotides to the unwound DNA
• Repeated many times - amount of DNA increases exponentially  

• Any therapeutic technique where functioning allele of particular gene is placed in cells of individual lacking the functioning allele for that particular gene
• Treats some recessive conditions but not dominant conditions 

SOMATIC:

• Functioning allele introduced into target somatic cells - removed, treated and replaced
• Short lived as somatic cells - repeated reguarly 
• Specialised cells wont divide to pass on allele 
• Hard to get allele into genome in functioning state
• Hosts become immune to viruses and liposomes inefficient 
• Restricted to patient - not passed onto offspring 

GERMLINE:

• Functioning allele introduced into germline cells - delivery more straightforward 
• All cells derived from germline cells have a copy 
• Unethical as it affects offspring - genetically engineering embryo, unsure of damage 
• Passed onto children 

• Religous objections 
• Fears of unforeseen effects of gene 
• Fears of consequence of escaping into wild 
• Growing GM plants may damage the environment 
• Eating GM plants may be bad for health 
• Microorganisms may transfer gene to another microorganism 
• Animal welfare 
• Organs for xenotransplantation 
• Plant resistance passed on - affect food chains 
• Germline cell patients dont get opinion as not born 
• Unpredictable effects of gene therapy 
• Germline gene therapy enhances desirable characteristics - lead to designer babies 

• Young leaves produce auxin - inhibits leaf loss
• As leaf gets older less auxin is produced
• Ethene is produced in older leaves - stimulates leaf loss
• Abscission layer of cells develops where leaf joins the stem - separates the leaf from the rest of the plant 
• Ethene stimulates cells in abscission layer to expand - breaks cell walls, leaf falls off
• Before leaf falls off - grows layer of protective tissue where leaf will break off - scar prevents entry of pathogens 
• Cells in the layer have suberin in cell walls 

• Impulse arrives - causes vesicles to fuse with the pre-synaptic membrane and release acetylcholine into the synaptic cleft 
• Acetylcholine diffuses across synpatic cleft and binds to receptors on sarcolemma of muscle cell causing depolarisation 
• Depolarisation travels down T tubules 
• Calcium ions are released from stores in sarcoplasmic reticulim 
• Bind to troponin in the muscle, leading to contraction 
• Acetylcholine esterase breaks down acetylcholine so contraction only occurs when impulses arrive 

• Voluntary = long multinucleate fibres
• Involuntary = short spindle shaped cells, single nucleate
• Cardiac = branched fibres, intercalated discs join cells at their ends 
• Voluntary and cardiac are striated, involuntary is unstriated 
• Voluntary = contracts and fatigues quickly 
• Involuntary = contracts and fatigues slowly 
• Cardiac = contracts quickly and doesnt fatigue 
• Voluntary = voluntary nervous system control 
• Involuntary = autonomic nervous system control 
• Cardiac = myogenic, autonomic control 
• Voluntary = voluntary movements of bones of the skeleton about joints 
• Involuntary = movement of materials along internal tubes and autonomic reflexes
• Cardiac = pumps blood around the body 

• Threat occurs - usually visual or auditory stimuli 
• Hypothalamus activated - stimulates activity in sympathetic nervous system 
• Causes release of adrenaline from adrenal medulla into blood 
• Hypothalamus releases corticotrophin releasing factor (CRF) into pituarity, causing the anterior pituarity gland to release ACTH 
• Stimulates release of corticosteroid hormones from adrenal cortex - help body to resist stressors 

Causes physiological changes:

• Increases blood pressure - less blood flows to gut and skin 
• Causes skin to turn pale 
• Smooth muscle in the gut and airways relaxes 
• Pupils dilate 
• Diaphragm and breathing rate increases 
• More blood flows to the skeletal muscles