Edexcel GCE Biology Unit 5 6BI05 June 2013

In order for a gene to be expressed or transcribed the transcription factors are required to be in their active state. The drug can basically inactivate these transcription factors thus preventing the transcription initiation complex from forming (which is the RNA polymerase combined with the transcription factors), and attaching onto the promoter region of the gene. So the gene essentially remains switched off.

Can anyone ex[plain the hole genome project thing? and the how the produce drugs with GMO?

I'm taking Chem 5 on Wednesday, that one isn't as frightening as Bio 5 though!

Also, in reply to your question, did you mean the production of Drugs by using GMOs (Plants, Microorganisms and Animals)?

Microorganisms -

First isolate a healthy gene which codes for the protein (drug) you wish to make, such as the human insulin gene. (You can link this with the Human Genome Project, which has helped us map out all the healthy genes for each protein etc).

Amplify the gene using the Polymerase Chain Reaction, to produce many copies of the gene.

Insert the Gene into a Plasmid (circle of DNA commonly found in Bacteria).

Modify the Bacteria with the plasmids (This step is awkward because the genes won't always take, however a good way of identifying which bacteria have taken up the genes is to also code a gene for antibiotic resistance too and insert that into the plasmid along with the gene for Insulin, then treat the bacteria with Antibiotics, the ones that survive are likely to be the ones who have taken the plasmid, so are the bacteria you want.)

Place the bacteria in a vat/storage whatever thing you wanna use to allow them to reproduce. They will now begin to produce the protein (drug) you want.

Advantages include producing large amounts of industrial enzymes cheaply and quickly, also Insulin made from GMOs which have human genes mean that the insulin made will be much more compatible with humans that, say, using Animal Insulin.

Disadvantages are that there is a risk of the bacteria getting into the general population (this seems to get you a mark, but if we're being realistic, this would never happen because scientist are smart enough to have made these GMOs unable to live outside the lab!), and playing god is ethically questionable!

Plants:

Insert therapeutic gene into Bacteria/Virus to be used as a Vector and infect the plant with this vector.

The pathogen will implant the genetic material into the plants genome for transcription. (Typically, they modify a bacteria which gives plants a type of 'plant cancer' then harvest the tumor cells because they know that these cells carry the gene for the drug).

Using these harvested cells a new plant is grown (remember how all plant cells are Totipotent and can grow and whole new plant?)

Now the plant will produce the drug in its fruit etc.

Advantages being that fruit doesn't require a lot of specialised storage, and (example bananas) can be grown in parts of the world that really need the drug and can be administered without specialist help (eating the Banana gives a dose of the drug, how special!). Also, when we're talking about just modifying plants for other things, you get massive yields and more resistance to predators and such.

Disadvantages are that some people fear that cross pollination could occur and these genes are spread across wild species which is not likely as most plants that are Genetically modified are also sterile so to prevent this, however making them sterile means they won't reproduce each yeah, thus a new supply has to be bought from the drug company which is expensive! Also, people get all freaky about eat GM crops, god knows why though.

Animals:

Genes coding for the desired protein are injected into a fertilised animal egg and this egg is implanted, so that the egg is carried to term and the animal produced has a genome coding for this protein.

When this animal comes of age, and starts producing milk (for example) the protein will also be produced in the milk, making this milk a source for this drug. Companies can then sell the milk as is (with the drug in it) or purify the drug by separating it from the milk.

Advantages of modifying animals are that, once you have modified the animal, it can reproduce and you can produce a herd or animals all able to produce the drug.

Disadvantages is that the products from the animals are very costly typically, which can lead to a two tier system (poor people can't afford so don't get treatment, where rich people can). Also, playing God again, bla bla.

Hope this helps, this is a heck of a post though.... sorry about that!

Edit: In my flurry of typing I made some awful spelling mistakes!

how does lactate makes NAD available? can someone explain please? thanks

Here is a post I did earlier about the whole GMOs producing drugs etc.



As for the Human Genome Project, this was a massive undertaking to map the entire genome (every gene) found in human DNA. Using data from this project can help with identifying which genes can cause certain diseases, which alleles give greater risk of certain cancers, it can help with personalising drugs as each persons genetic make up can have something to do with the way their body reacts with particular drugs (side effects and dosage etc) so knowing the genome of a person can help tailor a drug specific to that person. Also, by identifying all the genes we can make drugs which will specifically act as transcription factors for those genes, allowing better gene expression (or suppression etc).

How would you guys answer the core practical question on how to investigate the effects of exercise on tidal volume and breathing rate?

Using a spirometer, calibrated to correctly for volume. Get a group of people all of the same ethnic background or age (This is to control more variables to make the results more reliable and conclusion more valid), and get an average for each person of all their resting tidal volumes and breathing rates, Tidal volume is measured as the amplitude of a single wave on the spirometer trace, which is the distance between the highest point and lowest point, and breathing rate is how many of those waves occur in one minute.

Then put them on a treadmill and do it again (you could also just get them to stand at rest whilst using the spirometer and then get them to run on the treadmill so you can see the effects on one single trace.) Make sure each person is running at the same speed (more variable controlled). The differences in the spirometer traces are possibly because of the exercising. Take another average of tidal volume and breathing rate. Repeat with many people of different ages and backgrounds to test for differences there too.

Noone replied. I asked why the cells that were altered to contain cancer-causing genes were inserted into mice that had their immune systems compromised.

I probably should use Embryo though, it is the more scientific word. I don't know why I didn't at the time, sometimes in practice questions I write pretty decent stuff and then look at the mark scheme and realise that they give loads of marks if you just use the most scientific terminology possible. Hah, you should see my past papers, I think on every one I've written "Use more technical language!"

Is this exam usually tight for time? Does anyone know? Do you have to rush to get through it?

Last time I wasn't able to finish it- couldn't attempt 5 marks or so. But that's because I didn't read the pre-release booklet completely before sitting the exam, so had to keep trawling through the pages.

I also got bogged down quite a bit in some of the earlier questions.