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F215 - Revision thread 13th June 2011

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OCR just being evil? There doesn't seem to be a massive amount of application questions either! Though, i'm not complaining :smile:

They've probably saved them all for this paper :frown:

Reply 981

heartskippedabeat

Original post by amyyy24

They've probably saved them all for this paper :frown:

Hopefully not :frown:

Reply 982

lmfw

that would be evill :frown:

I just never understood that whole concept really, I can understand a few marks here and there being sypoptic but 20 marks? really??

Reply 983

Mcfilly

Original post by lmfw

I would agree :smile:

Literally just doing that question! Now thinking there was not much point :tongue:

Would definitely focus a LOT of meiosis though!!

Yeh! I think i will focus on that a bit more tomorrow! Anyone else just losing the will to live with this exam? lol

Reply 984

sportycricketer

Original post by lmfw

that would be evill :frown:

I just never understood that whole concept really, I can understand a few marks here and there being sypoptic but 20 marks? really??

Maybe they meant 20% Synoptic stuff over the cycle where they test EVERYTHING by? :wink:

Reply 985

lmfw

Original post by sportycricketer

Maybe they meant 20% Synoptic stuff over the cycle where they test EVERYTHING by? :wink:

haha maybe, just my teacher kept going on and on about how much of it is AS stuff and i'm like wait, that can't be right :tongue:

Reply 986

sportycricketer

Original post by lmfw

haha maybe, just my teacher kept going on and on about how much of it is AS stuff and i'm like wait, that can't be right :tongue:

lol my teacher too, and everyone on the thread :tongue:

do you think it's worth looking over last year's biology's Conservation module, theres so much to revise in this module anyway :s-smilie:

Reply 987

lmfw

Original post by sportycricketer

lol my teacher too, and everyone on the thread :tongue:

do you think it's worth looking over last year's biology's Conservation module, theres so much to revise in this module anyway :s-smilie:

Honestly? No. Looking at the F215 papers the synoptic questions have been like "what microscope was used", I'm sure we'll be able to remember things like that! Even if we can't it'll be like a two marks lost if that. I think i'll look through my AS stuff, probably the definitions and yeah, conservation. But not gonna stress about it :smile:

Reply 988

lmfw

Usefull!

Biotechnology and gene tech questions F215-1.rtf1782.8KB

Biotechnology and gene tech answers F215 (1).rtf327.1KB

Reply 989

ManPowa

Does anyone know how to calculated the expected value in the Chi-squared test?

Reply 990

Arab_Empress

Hey all,

I know the function of restriction endonuclease and what it does etc and I know it targets the restriction site on an DNA section, BUT does the enzyme have a complementary base sequence to the restriction site which has a specific base sequence (like DNA probe), or is it like all enzymes and has a particular active site and nothing to do with bases?

Reply 991

PenguinBoo

Original post by ManPowa

Does anyone know how to calculated the expected value in the Chi-squared test?

Done by the ratio.

e.g. with flower colour. If its a 1:1 phenotype relationship and theres 100 plants its expected that there will be 50 of one phenotype and 50 of another, but it might be that its observed as 43 of one and 57 of another.

Hope it helps.

Reply 992

Sohail92

What are the main things we need to know about the Hardy-Weinberg principle and using it to calculate allele frequencies? :confused:

thanks

Reply 993

science rules! :)

Yeh, this is true. It is essential to look at some mark schemes for questions which have long answers that are always the same, for example the process of tissue culture used in plant cloning, meiosis, genetic engineering, PCR and the flight or fight response. :smile:

Reply 994

science rules! :)

Restriction endonuclease enzymes cut a specific gene out of a strand of DNA at a specific restriction site. This exposes sticky ends. Then a vector such as a plasmid is cut using the same restriction endonuclease enzymes which exposes sticky ends. The plasmid and the gene cut from the strand of DNA then anneal by COMPLEMENTARY BASE PAIRING- as you said, using the enzyme DNA ligase. Covalent bonds form between the sugar and phosphate group.

(edited 12 years ago)

Reply 995

science rules! :)

To find the expected ratios for a chi squared test- you should be able to work them out from a genetic cross (ratios) or find them in the information that they give.

Reply 996

Kaph

I'm rubbish with meiosis. Anyone fancy explaining a few things to me? :wink:

I don't get the arrangement of chromosomes stuff. So in a cell, you have the maternal/paternal chromosome in each pair, so in Prophase 1 the homologous chromosomes are the original pair(one from each parent) and the replicated pair, and they line up opposite each other? Which makes up a bivalent?

I don't quite get diploid/haploid either.

Apologies. It's really the whole chromatid/chromosome thing that throws me off, the rest I can do. Ish.

Reply 997

ekta9

Original post by ManPowa

Does anyone know how to calculated the expected value in the Chi-squared test?

Basically you may be asked to work out a genetic diagram first and also be asked to work out the expected phenotypic ratio or they may just give you the ratio. For example say the ratio is 1 : 2 : 1 and the total amount of flowers that were produced were 280.

You then divide 280 by the total ratio (1 + 2 + 1) = 4. This equals to 70.
You then times 70 by each of the observed values in the categories and this should give you your expected value.

You can check that you've got it right by adding up your expected values which should come to a total of 280

Hope that helped :biggrin:

(edited 12 years ago)

Reply 998

science rules! :)

Hardy Weinberg (2's mean squared! Couldn't find correct key to change it!)

Use these 2 equations p2 + q2 +2pq = 1

p+ q =1

where p = dominant allele and q = recessive allele. Therefore 2pq- shows the heterozygous individual.

These two equations are then used to find out the allele frequency of the population- which is what Hardy Weinberg is used for.

The Hardy Weinberg equation makes the following assumptions;

Mating is random
There is no selective advantage for any genotype
There is no migration, mutation or genetic drift.
The population is large (to eliminate sampling error).

Reply 999

twelve

Original post by Kaph

I'm rubbish with meiosis. Anyone fancy explaining a few things to me? :wink:

Okay, in a cell, you're right - you have a paternal chromosome and a maternal chromosome. In interphase, they look like this:
| |

Then, in interphase, they replicate so that they look like this:
X X

In prophase, those two homologous chromosomes line up and form the bivalent like you said. They'll cross over, and the genes will get all mixed up ready for the divisions.

For the haploid/diploid thing, I think about it as a cycle:

Adult human - 2n ||
a chromosome from the mother, and one from the father
|
|
v
Gametes - n |
meiosis occurs, so that there is only half the genetic material - this will be a mixture of genes from the individuals parents
|
|
V
Zygote - 2n | |
gametes from the two parents join together, and then it starts again.