The Student Room Group

F215 - Revision thread 13th June 2011

Scroll to see replies

Reply 260
Original post by yesioo
Can someone explain epistasis? Meiosis and Variation is my weakest topic and I've got a horrible feeling it's going to be worth big marks.


Epistasis is the masking of a gene to express another. I suggest youtube as I can't explain it really on here.
For example if you have the genotype AaBb, AND we say that A is dominant to bb, then when we have A_ _ _ it wont matter what we have in the remaining 3. I don't know if I explained that properly tbh.
Original post by J DOT A
Guys, whats the difference between Primary and secondary metabolites.... and why is it that the production of primary metabolites is nearly nsync with the population growth of microorganism in a closed culture?


Primary metabolites are those that are produced as part of an organisms normal growth. It usually occur's in the Log/exponential phase due to the fact there is unlimited growth substances i.e. no limiting factors.

Whereas, secondary metabolites are those that are produced which are not part of the normal growth of an organisms such as penicillin. It occurs in stationary phase where the culture is described as being "under pressure" hence these substances are produced. They are usually produced after the main growth-exponential-phase.

And well for the last question I think the definition answers it. Its because primary metabolites are part of normal growth and therefore they grow at the same rate as microrganisms are being reproduced via binary fission due to the unlimited resources.

Hope this helps a bit.
Reply 262
Original post by slacker07906
Primary metabolites are those that are produced as part of an organisms normal growth. It usually occur's in the Log/exponential phase due to the fact there is unlimited growth substances i.e. no limiting factors.

Whereas, secondary metabolites are those that are produced which are not part of the normal growth of an organisms such as penicillin. It occurs in stationary phase where the culture is described as being "under pressure" hence these substances are produced. They are usually produced after the main growth-exponential-phase.

And well for the last question I think the definition answers it. Its because primary metabolites are part of normal growth and therefore they grow at the same rate as microrganisms are being reproduced via binary fission due to the unlimited resources.

Hope this helps a bit.


Oh so they are reproducing asexually so of course it will be Binary fission! Thanks for that, really helped:smile:
Reply 263
do we have to know details on the drosophila fruit fly?
Reply 264
plus do you guys actually read the HOW SCIENCE WORKS (green pages)? :s-smilie:
Original post by Viva009
do we have to know details on the drosophila fruit fly?


No not on syllabus.
Reply 266
I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

What does everyone think?
Reply 267
I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

What does everyone think?
Original post by LisaWilliams
I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

What does everyone think?


I'm also thinking an essay on Meiosis and it's significance in variation from the first module. Possibly something to do with Apoptosis?
Reply 269
I'm just about to have a look through the past papers/specification and see what hasn't been asked yet, but im thinking maybe nitrogen cycle? and probably meiosis too
Reply 270
Original post by LisaWilliams
I think there's going to be absolutely loads of the first module (Cellular Control and Variation) as there was so little of this in January. Lots of genetic questions, maybe an essay on translation/transcription. Definitely something on meiosis i.e. the behaviour of the chromosomes etc or how genetic variation is caused. Definitely Hardy-Weinberg and all the stuff on genetic drift/natural selection.

What does everyone think?


also, i doubt there'll be a proteinsynthesis essay as there was one in june 2010, i believee
(edited 12 years ago)
Guys how would you answer question 3 of this paper?
FIXED http://pastpapers.org/A2/biology/central-concepts/2006%20Jan%20QP.pdf
Woops sorry about that..although it looks like it's a bit more about the old syllabus
(edited 12 years ago)
Reply 272


we need to log in to look at the paper
Original post by katie93
we need to log in to look at the paper


fixed
I can't do hardy weinberg!!! LOL. Might spend an all day on it tomorrow. And as for meiosis and how it contributes to variation is crossin over, random distribution of chromosomes and random distribution of chromatids right?

Also, my teacher predicted the following things-

1. Meiosis- essay
2. Hardy weinberg
3. Succession- particularly deflected.
4, Galapagos islands
5. Nitrogen cycle
6. The movement of muscles-antagonistic
7.Cycle of muscle contraction
8. Electrophoresis
9, Somatic gene therapy.
10. Coppicing

Arghhhhh :frown: least I only need a D in this exam!
Reply 275
Original post by tesha_al
Guys how would you answer question 3 of this paper?
FIXED http://pastpapers.org/A2/biology/central-concepts/2006%20Jan%20QP.pdf
Woops sorry about that..although it looks like it's a bit more about the old syllabus


Yeah it is the old syllabus, but heres how i'd answer it anyway
3)a)i) A, B, E
ii) Females in stage A are diploid, and formed from the gametes of 2 random fleas mating, A females are more likely to contain a wider variety of alleles than those in stage D.
iii) C and D are both haploid, so mitosis will produce more haploid gametes (with same number of chromosomes)
b) In prophase 1, bivalents form between homologues. This leads to the formation of chiasmata and crossing over between maternal and paternal alleles occurs (exchanging of alleles) forming varied chromosomes. In metaphase I bivalents align randomly at the equator, so random assortment occurs and resulting cells may have any combination of maternal and paternal chromosomes. In metaphase II chromosomes align randomly on the equator, so random assortment occurs and resulting cells may have any combination of maternal/paternal chromatids
c) Parental genotypes: IoIo x IoIo, IaIb x IoIo, IaIa x IoIo, IaIb x IaIa
Baby blood group: O, B, A, AB

heres the mark scheme too: http://pastpapers.org/A2/biology/central-concepts/2006%20Jan%20MS.pdf
Reply 276
hopefully this will be useful to people struggling to get past paper questions together. my teacher made this up, basically just goes through every past paper from the old course and says what topic it's on, the trick is finding the paper online, paperbank has most of them though!
also does anybody know how the mark schemes will differ on the old papers compared to the new?

hope this is useful!
Original post by katie93
Yeah it is the old syllabus, but heres how i'd answer it anyway
3)a)i) A, B, E
ii) Females in stage A are diploid, and formed from the gametes of 2 random fleas mating, A females are more likely to contain a wider variety of alleles than those in stage D.
iii) C and D are both haploid, so mitosis will produce more haploid gametes (with same number of chromosomes)
b) In prophase 1, bivalents form between homologues. This leads to the formation of chiasmata and crossing over between maternal and paternal alleles occurs (exchanging of alleles) forming varied chromosomes. In metaphase I bivalents align randomly at the equator, so random assortment occurs and resulting cells may have any combination of maternal and paternal chromosomes. In metaphase II chromosomes align randomly on the equator, so random assortment occurs and resulting cells may have any combination of maternal/paternal chromatids
c) Parental genotypes: IoIo x IoIo, IaIb x IoIo, IaIa x IoIo, IaIb x IaIa
Baby blood group: O, B, A, AB

heres the mark scheme too: http://pastpapers.org/A2/biology/central-concepts/2006%20Jan%20MS.pdf

thanks yeah I looked at mark scheme and it was pretty vague but if its old syllabus then its fine!
..........
(edited 12 years ago)

Quick Reply

Latest