F215 - Revision thread 13th June 2011

Reply 1620

sillysal

9

bacterial conjugation anyone ? :s-smilie:

Reply 1621

786girl

Original post by sportycricketer

Can someone please help me with Succession? I know it and understand it but I was wondering if someone had an "easier" and summed up version of it which I might be able to write about in an essay form in the exam? This is for sand dunes btw :smile:

Would be greatt!

hey! ok so it took me ages to learn it aswell, ive tried to put it as simple as possible

1.PIONEER SPECIES: sea rocket- tolerate salt water spray, unstable sand and lack of fresh water (they are very tolerant!!) then a mini sand dune forms and these poor plants DIE & DECAY leaving behind precious nutrients in this mini dune (its like they sacrifice themselves and leave behind things to help the future colonisers lol)

2. SEA COUCH grass grows- underground stems:helps stabilise sand
3. stability INCREASES throughout and nutrients ACCUMULATE , then MARRAM grass grow which traps more sand
4.Sand dune and nutrients INCREASE so more plant colonise eg birds foot trecoil. they have bacteria in their root nodules which convert nitrogen to nitrates
so again nutrients increase more plants colonise and stabilise further until CLIMAX COMMUNITY is reached

remember: through succession, nutrients increase, stability increases and BIOMASS of plants increases

Reply 1622

786girl

Original post by sillysal

bacterial conjugation anyone ? :s-smilie:

its about the advantage to Microorganisms of the capacity to take up plasmid DNA
conjugation-swapping of genetic material amongst bacteria
-contributes to genetic variation which can lead to antibiotic resistance genes.
plasmids often contain genes associated with resistance to antibiotics (eg ampicillin) and the swapping of plasmids could be bad because it spreads the resistance amongst bacteria! which we obvs do not want.

Reply 1623

thepwince

Original post by 786girl

can someone explain REPLICA PLATING? i dont get what it says in the book

Bacterial plasmid has two genetic markers; the resistance for antibiotic ampycillin and the antibiotic tetracycline.
The gene for insuline, if taken up, is within the coding section for tetracycline, and so bacteria that have uptaken the recombinant DNA will not be able to transcribe the gene fully, and so no longer resistant to tetracycline.

Replica plating works on this principle;
-The bacteria are left to grow.
-Some of this bacteria are grown upon ampycillin agar, and tetracycline agar. (transfered with what i imagine is like a big stamp, so that the arrangement of the bacteria is kept constant - hard to describe)
-Those with the normal plasmid are resistant to both, and grow on both plates
-Those with recombinant plasmid grow on ampycillin and not tetracycline.
-Those with neither do not grow at all.

So by a process of elimination, those collonies on ampycillin but not tetracycline = recombinant, the ones you want and are identified by comparing the two distributions.

I hope this helps - its hard to describe the transfer, i think its enough to say 'by keeping track of the transfered collonies' - pretty much what the textbook says.

(edited 12 years ago)

Reply 1624

sickofexamz

Do you need full raw marks in this exam to get the full 150 ums marks??

Reply 1625

heartskippedabeat

10

Original post by sickofexamz

Do you need full raw marks in this exam to get the full 150 ums marks??

No, I'm not sure how many but I'm guessing you need around 80? as it'll be around the 60-65 mark for 120 UMS.

Reply 1626

sillysal

9

Original post by 786girl

its about the advantage to Microorganisms of the capacity to take up plasmid DNA
conjugation-swapping of genetic material amongst bacteria
-contributes to genetic variation which can lead to antibiotic resistance genes.
plasmids often contain genes associated with resistance to antibiotics (eg ampicillin) and the swapping of plasmids could be bad because it spreads the resistance amongst bacteria! which we obvs do not want.

thankyou i understand it now :smile:

Reply 1627

sillysal

9

will we have to know about both rocks and sand dunes for succession?

Reply 1628

sportycricketer

Original post by heartskippedabeat

No, I'm not sure how many but I'm guessing you need around 80? as it'll be around the 60-65 mark for 120 UMS.

Original post by sickofexamz

Do you need full raw marks in this exam to get the full 150 ums marks??

Provided its 60-65 for an A, for full marks its going to be like 72-77 for full marks :smile:

(i think)

Reply 1629

786girl

Original post by sillysal

will we have to know about both rocks and sand dunes for succession?

spec says one example, so one is good enough

Reply 1630

heartskippedabeat

10

Original post by sillysal

will we have to know about both rocks and sand dunes for succession?

I'd focus more on sand dunes because that's what the textbook is mostly on :smile:

Reply 1631

yesioo

15

The Nervous System
Gial Cells such as Scwann Cells

help nutrients from the body and into the neuronesand maintain the correct balance of ions in the tissue fluid surronding them.

Neurones - transmit action potentials

Central Nervous System

brain + spinal cord.
mostly intermediate neurones (short dendrited) + many synapses with futher neighbouring neurones.

Spinal Cord - extends from the base of the brain down to the first lumbar verterbra. Canal in the centre containing CSF with unmyenlinated neurones in the middle that appear grey.

Peripheral

All the neurones outside the brain and spinal cord (sensory + motor)

Sensory = outside of spinal cord in the dorsal root where they pick up imformation at receptors and transmit action potentials toward the cell bodies. AP goes to CNS.

Motor = cell bodies in spinal cord and carry action potentials from the CNS to effectors.

Autonomic

ALL motor neurones that supply the organs. AUTO = not voluntary. Smooth muscle, rate of heart, activities of exocrine glands.

Sympathetic - FIGHT OR FLIGHT

motor neurones = line in ganglia outside spinal cord.Axons pass out of ventral root to organs.

Either noradernaline or Acetylcholine

increase rate and force of heart contraction
contracts sphincter, releases glucose into blood.
eye dilates, relaxes cilary muscle for distant vision
increas in sweating

Parasympathetic - REST AND DIGEST

ALL BEGIN IN BRAIN
neurone does not branch - carries straight on to target neurone

Acetylcholine

reduces rate and force of heart
stimulates gland secretion, relaxes sphincter muscles, glygogen produced.
radial mucles constrict causing eyes to constrict
light increase in palm sweating

Fell free to correct!

ok thanks!

Original post by 786girl

hey! ok so it took me ages to learn it aswell, ive tried to put it as simple as possible

1.PIONEER SPECIES: sea rocket- tolerate salt water spray, unstable sand and lack of fresh water (they are very tolerant!!) then a mini sand dune forms and these poor plants DIE & DECAY leaving behind precious nutrients in this mini dune (its like they sacrifice themselves and leave behind things to help the future colonisers lol)

2. SEA COUCH grass grows- underground stems:helps stabilise sand
3. stability INCREASES throughout and nutrients ACCUMULATE , then MARRAM grass grow which traps more sand
4.Sand dune and nutrients INCREASE so more plant colonise eg birds foot trecoil. they have bacteria in their root nodules which convert nitrogen to nitrates
so again nutrients increase more plants colonise and stabilise further until CLIMAX COMMUNITY is reached

remember: through succession, nutrients increase, stability increases and BIOMASS of plants increases

Thanks!

Reply 1634

periwinkle304

8

so if there's like a big question on 'outline how to sequence the genome of an organism', what would you say? would it be the sequence of events that starts with mapping the genome, then mechanically shearing or whatever? and does pcr come into that at all, or is it only automated sequencing? so confused :frown:

Reply 1635

sickofexamz

Original post by heartskippedabeat

No, I'm not sure how many but I'm guessing you need around 80? as it'll be around the 60-65 mark for 120 UMS.

Thanx thats gud to know as i need about 130 ums marks for an A overall so i was thinking that i'd need realli high raw marks.

Reply 1636

-Jaz-

Original post by sillysal

bacterial conjugation anyone ? :s-smilie:

1. A conjugation tube forms between two bacteria
2. A nick forms in the plasmid of one bacteria
3. The plasmid unravels and is passed into the next bacteria
4. The exposed bases are replicated
5. The new plasmid and the old coil back into circles again
6. Nicks are sealed by DNA ligase
7. The conjugation tube breaks off

Helpful? :smile:

Reply 1637

-Jaz-

Original post by periwinkle304

so if there's like a big question on 'outline how to sequence the genome of an organism', what would you say? would it be the sequence of events that starts with mapping the genome, then mechanically shearing or whatever? and does pcr come into that at all, or is it only automated sequencing? so confused :frown:

Yepp, it would just be the sequencing, mechanically shearing, etc. Might as well include PCR to be on the safe side, because sometimes the biology mark scheme can be iffy. :smile:

Reply 1638

sickofexamz

Hey could someone clarify this for me. In the heinemann book on 2.2 spread 4 do we need to know the information in the table or is it just the paragraph under the table?
Thanx

Reply 1639

slacker07906

OP

16

LOL I dont know anything. Going to revise till late tonight. Can you claim special circumstances if a family member (dad) has been in hospital?