OCR Biology F215 Control, Genomes and Environment Fri 15 June 2012

Ultrafiltration is the filtration of blood in the glomerulus, where large molecules such as proteins and red blood cells cannot pass through the basement membrane and molecules such as amino acids, urea, glucose and water can pass the plasma membrane into the bowmans capsule. The relative molecular mass is 69000.

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Ultrafiltration is the filtration of blood in the glomerulus, where large molecules such as proteins and red blood cells cannot pass through the basement membrane and molecules such as amino acids, urea, glucose and water can pass the plasma membrane into the bowmans capsule. The relative molecular mass is 69000.

This was posted from The Student Room's Android App on my HTC Desire HD A9191

introns are present within all genes along with exons. they are both transribed into pre-mRNA but during modification of this pre-mRNA the introns are 'cut-out' leaving only the exons in the mRNA to be translated. An easy way to think of it is the exons are the only ones which are expressed

oh right got it but the advantage i said was in the ocr purple book but doesnt matter i got it

Outline PCR and give 2 differences between dna replication and PCR(8)

Polymerase chain reaction (PCR) is carried out in a thermocycler with a solution containing: samples of the DNA wished to be replicated, thermophillic DNA polymerase, free DNA nucletoides and DNA primers.

1) The sample of DNA is placed within the theremocycler and the temperature is raised to 95 degress C. This causes the hydrogen bonds between complementary nucleotides to break exposing the organic bases (ie strands seperate)
2) The reaction mixture is cooled to 55 degrees C and DNA primers are added. The primers anneal at the 3' ends of the strands.
3) The temperature is raised to 72 degrees C allowing the DNA polyermase to bind to the DNA primers while simultanously the free nucletoides base pair to their complementary exposed nulceotides on the strand (hydrogen bonding). The DNA polymerase enzyme then moves down the strand catalysing the formation of phosphodiester bonds between the adjacent nucleotides (ie forms the sugar phosphate backbone).
4) the entire process repeats many times to produce a large number of identical copies of the original DNA sample.

2 differences to standard cellular DNA replication:
1) In Standard cellular DNA replication the temperature remains constant therefore whereas in PCR the temperature seperates the DNA strands allowing free DNA nucleotides to attach in cellular DNA replication the enzyme helicase seperates the strands.
2) During PCR, DNA primers are required to allow the DNA polymerase enzyme to attach to the DNA whereas in cellular DNA replication these are not required.

Perfect but you will lose 1 mark for differences cause the part about DNA is correct but you forgot to metion the cooling and heating separates the strands but good

my turn

introns are present within all genes along with exons. they are both transribed into pre-mRNA but during modification of this pre-mRNA the introns are 'cut-out' leaving only the exons in the mRNA to be translated. An easy way to think of it is the exons are the only ones which are expressed

so during genetic engineering, the reverse transcriptase enzyme produces an complementary dna strand without the introns correct?

Outline the process of Replica plating (6+1)

Outline the process of Replica plating (6+1)

I dont think so! never heard my teacher telling us about it! so we are good to ignore it

Pretty good answer - i'd say it'd be at least 4 out of the 6 if not 5 but you may want to be a little more careful with your wording.

ie for the nuclear transfer method (in sheep) i'd answer as such:
A cluster of mammary cells are taken from the individual wishing to be cloned and grown in culture, a cell is then isolated from this culture of mammary cells. An ovum is isolated from another sperate individual of another breed of sheep and is enucleated (nuclues removed), the enucleated ovum and isolated mammary cell are then combined via electro-fusion to produce a reconstructed cell with the nucleus of the individual to be cloned and the cytoplasm of the other. This recontructed cell is then cultured in a tied oviduct of a sheep before being recovered as an early embryo and implanted into a surrogates uterus where it is allowed to develop as a normal embryo would.

For cloning via artificial embryo splitting i'd go about it as such:
Gametes are collected from two carefully chosen parents - usually chosen for favourable charactersistics such as a high milk yield in cows or tender meat. The male may even undergo lineage testing to identify the characteristics of the young he has farthered. Once the gametes are collected they are allowed to fertilise one another in vitro forming an embryo, this embryo is then allowed to grow/divide in vitro until a 16-cell embryo is produced (number may be different eg may be 32 etc). This embryo is then split into several seperate segments with an equal number of cells. These segments are then implanted into surrogate mothers and allowed to develop as normal producing offspring which can be described as clones of one another.

Advantages:
rare animals can be cloned for preservation of the species
High value (desirable phenotyped) animals can be quickly reproduced
GM animals eg goats which produce pharmaceuticals in their milk can quickly be reproduced

Disadvantages:
High value animals are not specifically produced with animal welfare in mind - ie may cause suffering of certain animals (hence ethical objections)
Genetic uniformity of organisms will make all individules suceptible to the same disease should one arise/develop ie unable to adapt to changes in environment due to lack of variation.
Unclear as to whether cloning has an effect upon the aging of organisms prematurely

The bacterias are grown in normal nutrient growth medium .
two different types of bacteria are grown in culture one with tetracylcine and the other with ampilcinine(gel) agar the bacteria that grows on amipicin gel agar is the bacteria that has the plasmid for human insulin gene and these are grown to form colonies of the same bacteria.

I prepared my answer in advance and I must say your answer are somewhat more concise than mine

Bacterial Plasmids containg 2 genes coding for 2 specific products making the bacteria immune to 2 specific antibiotics are chosen. These resistance genes are known as Genetic Markers.
The plasmids are cut out by a restriction enzyme carefully selected to ensure its restriction site lies within the centre of one of these genetic markers. This will mean that upon the desired gene being inserted this resistance gene will no long be correctly transcribed therefore it will not be correctly expressed meaning bacteria with the desired modified Transgenic plasmid will onyl be resistant to one of the two antibiotics.
This process is carried out as upon being cut by the restriction enzyme and mixed with samples of the desired gene also cut with the same restriction enzyme (hence having the same complementary sticky ends) the plasmids could potentially just reseal themselves with taking up the gene and similarily the gene could itself form a cylic DNA molecule. This process allows for bacteria with the correct plasmid (mixture of the plasmid and the gene) to be selected for and hence grown seperatly in culture producing the desired product)

The actual process is carried out as follows:
1) The bacteria (following the insertion of the plasmids back into the bacteria) are grown on a nutrient/mineral rich agar plate allowing seperate colonies to form.
2) samples of cells from each colony are transferred to a seperate agar plate coated in the antibiotic for which the gene should still be expressed (ie the one which didn't have the gene inserted into the centre of it)
3) once these cells have formed new colonies, further cells are taken from these new colonies and transferred to one further agar plate coated in the second antibiotic to which the bacteria containing the desired modified plasmid should be suseptible to.
4) By keeping track of which colony has come from which the bacteria containg the correct plasmid can therefore be identified, sample of it can be taken and grown in culture on a large scale hence producing the desired produce on a mass scale without competition from bacteria not producing the product hence a better yield of product.

Literally memorising your notes here. But a little unsure about nuclear transfer. Do we need to take egg cell from ANOTHER BREED of sheep or should it be in the same species, just another female sheep, who is to be surrogate to the altered embryo?

so would i get the marks cause its like the key words that gets you the marks i summarised so is it a well done or not?

The ovum can be taken from either the same or a different breed but generally it is a different breed just because the breed being cloned is much rarer and it isn't generally viable to isolate an ovum from a female of this rarer breed.

OH. Ok. I see, I can understand the use of a more common sheep breed if the clone is of a rare species. I was simply wondering, in general, like the case with Dolly. Thanks

hey do u want to continue/