F215 - Revision thread 13th June 2011

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Reply 1340

Arab_Empress

Is a germline cell just a cell like a gamete that develops into a being?

Reply 1341

sportycricketer

Original post by sillysal

are you retaking too?

I'm retaking too :smile:

lol

Reply 1342

sillysal

can someone explain to me what we need to know about the drosophila please?

i understand the concept of the homeotic genes and how they control body plan development.

Im just stuck on the whole mitosis part of it :frown:

(page 114 in ocr textbook)

Reply 1343

Arab_Empress

Original post by sillysal

(page 114 in ocr textbook)

I would explain to you but i really dont know how much we actually need to know off that page

Reply 1344

sillysal

Original post by Arab_Empress

I would explain to you but i really dont know how much we actually need to know off that page

lol any knowledge you have of it would help :smile:

i have a feeling it will come up

Reply 1345

sillysal

Original post by Arab_Empress

Is a germline cell just a cell like a gamete that develops into a being?

yeh it is a sex cell and so offspring are produced from these cells

Reply 1346

Arab_Empress

Original post by sillysal

lol any knowledge you have of it would help :smile:

i have a feeling it will come up

Im trying to look for summarised notes about the homeobox:

Homeobox genes: control the development of the body plan
Consist of 180base pairs (the homeobox) which code for polypeps of 60amino acids
SOME are transcription factors, which bind to DNA upstream and initiate transcription, thus regulating expression of other genes

They're arranged in Hox clusters, the more complicated the organism, the more clusters
They're activated and expressed from anterior to posterior.

Drosophila, reproduces rapidly, has only 4 chromosomes,

Fruit flies are highly specialized insects with 2
wings and 3 body segments. Their ancestors had 4 wings and many body segments. The fruit fly
embryo starts out with a series of 16 equal-sized segments. Various segments merge to make the 3 segments we recognize as the head, thorax, and abdomen.

And the part below is from a thread about the homeobox:

1. Every organism contains genes which are classed as 'homeotic genes' or you might see them called 'hox genes' OR 'homeobox genes' (these last two genes (which are the same gene but are different names for it!) only control body plan development for specific organisms like the fruit fly and most animals I'm aware of so they are the most common type of homeotic gene); I will refer to them as homeotic genes. One of these genes, like any other gene, is a section of DNA and so it would coded for by a particular series of bases.

2. The homeotic genes have regions called homeobox sequences (made up of 180 nucleotides/ bases), so there is one homeobox sequence coded for by each homeotic gene.

3. This homeobox sequence codes for a 60 amino acid long protein domain known as the homeodomain. An amino acid is made up of 3 bases (or one triplet/codon for use of other words) and so you can see that this adds up to the original 180 base section of DNA that codes for the homeobox sequence which is ultimately coding for the homeodomain.

4. This homeodomain binds to different sites on the DNA (at the start of developmental genes) so this protein acts as a transcription factor - it either activates or represses transcription on certain sites of the DNA and so alters the production of proteins which are involved in the development of the body plan

(edited 12 years ago)

Reply 1347

starburst92

Is everyone memorising the whole of the nitrogen cycle or just the main points thats on the next page? and are you memorising the sequence of how bread wheat has 42 chromosomes? or just the fact that it goes through two mutations that double the amount of chromosomes?

Reply 1348

heartskippedabeat

Original post by sillysal

tell me about it, i hate balancing out revision, so hard to sort out what's priority lol, im retaking f214 and have hardly done any revision for that although it doesnt look half as bad as what it did first time round :P

i'm retaking it too and yeah i've hardly looked at it :/ i wish they'd put it before f215, would've made a lot more sense :tongue:

i did really badly in january though, i thought the paper was horrible :frown:

what overall grade do you need/want?

Reply 1349

heartskippedabeat

Original post by Suren_x

Yup, have to finish module 3 today. Its so boring -_-

How did it go? yeah this module's so big and boring :/ i can't get any of it to stick in my head :frown:

Reply 1350

YuDunno

Original post by starburst92

I've just learnt the main processes and the bacteria involved.. the whole point is that Nitrogen gas can't really do much unless it's part of a compound, so there are 4 ways that we need to know of how nitrogen can be fixed in to compounds, then how it can be converted to make the product required for plants (nitrates) and that the nitrogen can be released in to the air again, either by decomposition of organic matter or the denitrification of the nitrates.

Nitrogen fixation
- By lightning, forms nitrogen oxide
- By the bacteria Rhizobium in leguminous plants, which have a mutualistic relationship give the bacteria carbon based compounds such as glucose
- By bacteria in the soil
- By the Haber Process which forms NH4+ and NO3- ions in fertiliser

Nitrification

Ammonium converted to NITRITES using the bacteria Nitrosomonas NITRITES then converted to NITRATES using the enzyme Nitrobacter. The Nitrates can be taken up by plants and used to form Amino Acids.. the plants are then eaten by animals.. When animals die they "decompose" in the soil with the help of the decomposers.. which are also bacteria..

Denitrification

When the Nitrates are dentrified the nitrogen is released back in to the atmosphere as N2, nitrogen gas. Usually some bacteria involved that we don't need to know the name of.

I hope this is of some help and is right... :redface:

Reply 1351

YuDunno

Original post by heartskippedabeat

Me too

There's soooo much content and the synoptic element is stressing me out haha :/

I just resat f212 so I'm not too bad with that but it's f211 and f214 that are worrying me!

My teacher is predicting 20% of the paper to be synoptic :confused:

I don't know how to revise anymore :frown:

I've run out of strategies, the old past paper questions, alot of the stuff isn't on our spec so it's really offputting when I'm worrying about a question for 15minutes then realise I've never heard of the terms in the mark scheme!

Reply 1352

Mariam8

can someone please explain the sliding filament model? i really don't understand it... thanks :smile:

Reply 1353

heartskippedabeat

Original post by YuDunno

I just resat f212 so I'm not too bad with that but it's f211 and f214 that are worrying me!

My teacher is predicting 20% of the paper to be synoptic :confused:

I don't know how to revise anymore :frown:

I think most of the synoptic stuff will be from f212 and f214, there's not much they can link to f211, hopefully anyway.
Yeah, OCR have said the f215 papers are 20% synoptic but when I've done the past papers not much seems to be :s-smilie:

Still I wouldn't put it past them to throw in something completely random!

Ahh yeah, I've avoided the old past papers for exactly that reason, but I might go through them today and pick out the relevant questions. It's so annoying though, I wish there were more full past papers :/
How did f212 go? :smile:

Reply 1354

YuDunno

Original post by heartskippedabeat

Yeah I hope that's the case, F211 was too long ago :frown:

F212 went well thanks, I was resitting it the 3rd time :redface:

Got a B last summer, and a B again in January, hopefully it's an A this time though :smile:

as it was really bugging me because I had an A from f211 and f214..

I'm going to go through the list of topics our teacher predicted will come up, then I shall return to enlighten the TSRians if I have any devine intervention while I am away. :cool:

Work hardd!!!!

Reply 1355

science rules! :)

Original post by Arab_Empress

Is a germline cell just a cell like a gamete that develops into a being?

Yeh, just a description of an embryo. We need to know some key differences between somatic gene cell therapy and germline gene cell therapy. Changes to germline cells in germline cell therapy ccan be passed onto offspring, wheras in somatic cell therapy changes to the genome are restricted to the actual patient. In germline cell therapy it is easier to insert the allele in its functioning state into the germline cells, however their are ethical issues about altering the human embryo. With somatic cell therapy, it is more difficult to insert the allele into the and target cells e.g techniques which are difficult must be used e.g. ex vivo. With somatic cell therapy, it may need to be repeated regularly because treatment is short-lived, wheras germline cell gene therapy is permenant modification to the germline. All cells derived from germline gene cell therapy contain a functioning copy of the allele. With somatic cell gene therapy it is difficult to insert the allele in its functioning state- use of genetically modified viruses and liposomes. Inserting an allele into an embryo in germline gene cell therapy is easire but may cause uintentional changes. It is considered unethical to engineer human embryos. :smile:

Reply 1356

heartskippedabeat

Original post by YuDunno

Yeah I hope that's the case, F211 was too long ago :frown:

F212 went well thanks, I was resitting it the 3rd time :redface:

Got a B last summer, and a B again in January, hopefully it's an A this time though :smile:

Work hardd!!!!

Aww I'm sure you'll have got anA this time round :biggrin:

Can I be cheeky and ask what topics she's predicted? :tongue:

My teachers have been pretty useless haha :redface:

You too!!

Reply 1357

Suren_x

Original post by heartskippedabeat

How did it go? yeah this module's so big and boring :/ i can't get any of it to stick in my head :frown:

Yeah I managed to revise most of it and reviewed Humans and Galapagos and then crashed hard because I started hallucinating lol :eek:

Reply 1358

greenford

so..what kind of grades do people need to got to get onto their course ?

Reply 1359

science rules! :)

Original post by Mariam8

can someone please explain the sliding filament model? i really don't understand it... thanks :smile:

The sliding filament model controls muscle contraction. When a muscle is not contracting a molecule onf tropomyosin covers the binding site for the myosin head group on actin, and is held in place by troponin. When an action potential arrives, calcium ions are released into the sarcoplasmic reticulum and bind to troponin molecules. The shape of troponin changes and tropomyosin moves away from the binding site on actin.

The myosin head attaches to the actin filaments- a cross bridge is formed.
The myosin head bends and pulls the thin (actin filament) over teh thick myosin filament. This is called the POWER STROKE>
ADP and Pi are released.

The cross bridge is then broken and ATP attaches to the myosin head.
The head moves backwards as the ATP is hydrolysed to ADP and Pi and can form a cross bridge with a thin filament further along.

How is teh ATP supply maintained?
Aerobic respiration in muscle cell mitochondria produces ATP providing there is enough oxygen and respiratory substrate.
Anaerobic respiration in muscle cell sarcoplasm (leads to roduction of lactic acid which is toxic- released into blood and redirects blood to muscles)
Transfer of phosphate group from creatine phosphate in muscle cell sarcoplasm to ADP to form ATP. Catalysed by creatine phosphotransferase.