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F215 - Revision thread 13th June 2011

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does anyone understand that fishy spread on gene therapy? also the one about classifying species, both have left me totally baffled :s-smilie:

Basically what gene therapy is the therapeutic technique used to transfer dominant alleles into people who have disease due to being homozygous recessive and therefore don't produce a functioning protein such as cystic fibrosis- CFTR gene.

There is somatic and germline gene therapy.

In somatic the desired gene coding for the functioning proteins is inserted into a fully differentiated human cell. so for cystic fibrosis the CFTR gene is transferred into the epithelial cells in the respiratory tract to produce the functioning enzyme. However, as the gene is only inserted into the cells requiring the functioning proteins it is not passed onto offspring and needs to be reapplied.

Whereas in germline gene therapy, the gene is inserted into embryo's which may grow up to become adults. All the cells would contain the gene including the testes and ovaries so it is passed onto offspring and also it doesn't need to be reapplied. Currently illegal in the UK.

Reply 361

slacker07906

Can anyone explain to me what the homeobox genes actually do?

Reply 362

TobeTheHero

Original post by slacker07906

Can anyone explain to me what the homeobox genes actually do?

Will it come up?

Reply 363

slacker07906

Original post by 786girl

what are the chances of the NITROGEN CYCLE coming up?
i have never studied it bfore except at A2 where my teacher assumed we all had background knowldege on it, its one of those things thats just not going into my head!!
what main points to we need to kno?

I'd learn all of it as I think its likely to come up.

- nitrogen gas in the atmosphere is used by rhizobium bacteria. These bacteria living in the nodules of legume species convert nitrogen gas into ammonia and amine compounds. These amine compounds are then transported by the plant from the nodules and used to make amino acids then proteins. This is known as nitrogen fixation. It should also be noted that a mutualism is formed as each organisms benefits as the rhizobium gains carbohydrates from the plant.
- the next stage is nitrification. Plants support food webs throughout which exretion, death and production of faeces take place. This is of benefit to the ecosystem, but first decomposition by saprobiotic bacteria has to take place. What happens is a waste product ammonia is formed.
-ammonia is needed by nitrosomonas bacteria for chemo-autotrophic nutrition. A waste product of this is nitrite.
- the nitrite is needed by the nitrobacter for the same type of nutrition. However, this time a waste product called nitrate is formed.
- The final stage is denitrification. The nitrogen gas is returned to the atmosphere by denitrifying bacteria such as pseudomonas. Some nitrate is converted back to nitrogen gas by these bacteria. the cycle is complete,

Reply 364

slacker07906

Original post by TobeTheHero

Will it come up?

Well if I knew what was going to come I wouldn't need to worry would I? Lol jk. But can you help me?

Reply 365

TobeTheHero

Original post by slacker07906

Well if I knew what was going to come I wouldn't need to worry would I? Lol jk. But can you help me?

lol i have no idea myself :frown:

I need to go through it again thoroughly :colondollar:

Reply 366

ManPowa

Original post by slacker07906

Can anyone explain to me what the homeobox genes actually do?

Homeotic genes are similar in plants, animals and fungi. These genes control the
development of body plans and are expressed in specific patterns and in particular stages
of development depending on when they are activated.
The homeobox is a sequence of DNA that codes for a region of 60 amino acids, and the
resulting protein is found in most, if not all, eukaryotes. The region binds to DNA so that
they can regulate transcription. In animals the homeobox is common in genes concerned
with the control of developmental events, such as segmentation, the establishment of the
anterior-posterior axis and the activation of genes coding for body parts such as limbs

Reply 367

There will be Particles

Original post by Waqar Y

20% of the paper is synoptic.

Seriously? Every single time?

Reply 368

ekta9

Can someone explain to me how to work out the frequency of an allele?! Really don't understand it! also I hope Lac Operon comes up as its pretty easy :smile:

Reply 369

There will be Particles

Original post by ekta9

Can someone explain to me how to work out the frequency of an allele?! Really don't understand it! also I hope Lac Operon comes up as its pretty easy :smile:

p+q=1 total proportion of allele

p^2 + q^2 + 2pq =1 total proportion of genotype

p is dominant allele
q is recessive allele

q^2 is recessive genotype (for example cystic fibrosis sufferer would have this)
p^2 is dominant genotype

you're usually given some values and you just plug them in really to find the proportion of one allele then u just work out what it would be as a percentage and times it by the total population. :smile:

Reply 370

slacker07906

Who's revising? I'm so tired!!!

Reply 371

.r.

Original post by slacker07906

Can anyone explain to me what the homeobox genes actually do?

Homeobox genes control the development of the body plan of an organism (e.g. animal, plant or fungi), with control over the polarity and positioning of organs - basically they determine where what goes..
Maternal-Effect genes determine which end of the embryo is anterior and posterior. Segmentation genes specify the polarity of each segment. Homeotic Selector genes determine the development of the head, thorax and abdominal segments. Md, Mx and Lb make the head; T1, T2 and T3 make the thorax and A1-A8 make the abdomen.
That's all I'm learning for it. And for some reason the name 'Drosophilia melanogaster' has been embedded in my memory which is on the same spread lol. have fun revisin!

Reply 372

ibysaiyan

Original post by .r.

Just to let you all know,a question based on the bold bit was in the june 10 paper. =]

Reply 373

.r.

Original post by ibysaiyan

Just to let you all know,a question based on the bold bit was in the june 10 paper. =]

that's a bit..in-depth :s-smilie:

what was the question, if you can remember?
i'm easily distracted lol, i was meant to be doing psychology right now!!

Reply 374

ibysaiyan

Original post by .r.

that's a bit..in-depth :s-smilie:

what was the question, if you can remember?
i'm easily distracted lol, i was meant to be doing psychology right now!!

I think the first bit asked about the definition of homeo genes and the next wanted to know about the segments of fliers,etc.. that was almost a year back =/

Reply 375

.r.

Original post by ibysaiyan

I think the first bit asked about the definition of homeo genes and the next wanted to know about the segments of fliers,etc.. that was almost a year back =/

ah well...really don't like all these application questions. i'm literally falling asleep on the keyboard lol so i'll call it a night now! :tongue:

Reply 376

greenford

anyone tries using the cgp book... it explain everything in detail and is so simple to understand.... the text book give you some info that you don't actually need to know....

U know hardy Weinberg .... the only thing we can be asked is calculation right?

Reply 377

ekta9

Original post by There will be Particles

Thank-you!! that makes it a little easier :biggrin:

Reply 378

182blink

does anyone knwo the grade boundries for this unit would be or for Jan 2011 paper ? :smile:

Reply 379

twelve

Original post by 182blink

does anyone knwo the grade boundries for this unit would be or for Jan 2011 paper ? :smile:

I think I did that paper for a mock, and the grade boundaries were something like 60% for an A. I don't know if it was that paper, but they're usually quite low apparently.