Turn on thread page Beta
    Offline

    0
    ReputationRep:
    (Original post by I Have No Imagination)
    Okay thanks.

    Umm how would you explain how mutations have harmful or beneficial effect? The book just gives a really long example..?
    Harmful - disadvantageous to survival, an example is a case of cystic fibrosis. A mutation (deletion) of 3 bases in the CTFR (cystic fibrosis transmembrane regulator protein) means that it cannot fold properly and thus it cannot carry out its function. Therefore excess mucus production and so its harmful

    Beneficial - advantageous to survival, an example is that bacteria have enzymes that break down antiobiotics, e.g. antibiotic resistance, a mutation could cause a change of base in the protein making it resistant to a wider range of antiobiotics and thus enhances its survival.

    I think thats right. Although i dont know about the somatic mutations, what do you mean by germline cells? do we have to know this smflesh?
    Offline

    1
    ReputationRep:
    (Original post by I Have No Imagination)
    Okay thanks.

    Umm how would you explain how mutations have harmful or beneficial effect? The book just gives a really long example..?
    Beneficial - advantageous, increasing the organisms chances of survival. e.g. you could talk about antibiotic resistance.

    Harmful - disadvantageous, decreasing the organisms chances of survival. e.g. Cystic Fibrosis.
    Offline

    0
    ReputationRep:
    OMG I didn't know this thread existed! Im so late lol
    Oh well a month from now it'll all be over
    Offline

    0
    ReputationRep:
    And now i believe is the time for me to panic, so much left to learn I think imma do bio the rest of today. Bricking it.
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    And now i believe is the time for me to panic, so much left to learn I think imma do bio the rest of today. Bricking it.
    Please...I'm still on frikkin meiosis! :eek:
    Offline

    0
    ReputationRep:
    (Original post by I Have No Imagination)
    Please...I'm still on frikkin meiosis! :eek:
    I used a revision guide for most of it and sometimes the textbook. The textbook takes so long hence learning rev guide then checking for things i missed. then i failed jan so ive gotta learn all that again -.-

    Meiosis:
    Used to produce gametes which are haploid, when they fuse together it becomes a zygote which is diploid and so they divide and develop. Happens in the reproductive organs - ovaries and testes.
    2 stages - Meiosis 1 and 2, in one there is only one cell where its visible, for the 2nd stage theres 2 cells visible and it happens at right angles to meiosis 1.

    Interphase happens which replicates DNA and organelles then:

    Meoisis 1-
    Homologous pairs come together to form a bivalent. One chromosome is maternal and the other is paternal. Genes are at the same loci on these.
    Prophase 1:Non-sister chromatids (e.g. ones with diff alleles) cross over at points called chiasmata (these can brak off and be swapped around so causing genetic variation - called resassortment or recombination due to crossover or crossing over).
    The nuclear envelope breaks down and the nucleous disappears too. Centrioles at poles of a cell begin to form spindle fibres.

    Metaphase 1: The bivalents line up randomly along the spindle fibre equator which leads to random segregation during anaphase (called random assortment of chromosomes). The spindle fibres attach to the centromere of EACH chromosome in the homologous pair

    Anaphase 1: The spindle fibres contract which pulls one member chromosome from each homologous pair goes to the poles of the cell. Centromeres do NOT divide. Where there are chiasmata, the crossed over parts go with the chromosome the new one they joined too.

    Telo 1: In animal cells, the genetic material has a nuclear envelope formed around it and the cells then divide by cytokinesis and chromosomes then uncoil.
    In plant cells they go straight to metaphase 2.

    Pro 2: If a nuclear envelope present, it breaks down and spindle fibres begin to form and chromosomes condense.

    Meta 2: Random assortment of the chromatids along spindle fibres equator allows random segregation during ana 2 so greater genetic variation. Spindle fibres attach at centromeres.

    Ana 2: spindle fibres shorten and chromosomes pulled apart at centromeres, each chromatid goes to the opposite poles of the cells (depending on assortment which side).

    Telo 2: Animals -> nuclear envelope forms and then they divide to form 4 cells.
    Plants --> a tetrad of cells is formed straight away.
    In both all cells are now haploid and have much greater variation
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    I used a revision guide for most of it and sometimes the textbook. The textbook takes so long hence learning rev guide then checking for things i missed. then i failed jan so ive gotta learn all that again -.-
    No, don't use the revision guide as your base because that's what I did aswell for jan and also failed miserably. Use the book and actually try to understand it, it makes so much more sense than way..
    Offline

    0
    ReputationRep:
    Has anyone started revising AS again? Our teacher keeps telling us this is MAJORLY synoptic, but our class has yet to start revising AS again. EEeeeeeepp!
    Offline

    12
    ReputationRep:
    (Original post by zoop)
    Has anyone started revising AS again? Our teacher keeps telling us this is MAJORLY synoptic, but our class has yet to start revising AS again. EEeeeeeepp!
    wtf ? I have yet to start proper revision for this unit.
    Offline

    0
    ReputationRep:
    (Original post by uer23)
    wtf ? I have yet to start proper revision for this unit.
    Oh boy, your going to have fun

    But I Have No Imagination, im finding that the majority listed in the textbook is the same as this rev guide. Theres just some pointlessly long paras which go round the explanation which are not vital. Im reading it and only found a few minor things, such as that chromosomal mutations are somatic mutations and are not passed on, they only really take place in mitosis at interphase. They can happen during meiosis but it will give rise to a new allele and so genetic variation and if they take place in the egg or sperm, the mutated allele will be present in every cell.

    Also found out that cystic fibrosis transmembrane regulator protein forms the channel that maintains Cl- and water across the membrane, the mutation causes it to be unable to transport the water and Cl- ions and so it means the cilia are dehyrdated and thus cant shift mucus which means mucus build up + infections.

    Wow reading it seemed to work O.O
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    Oh boy, your going to have fun

    But I Have No Imagination, im finding that the majority listed in the textbook is the same as this rev guide. Theres just some pointlessly long paras which go round the explanation which are not vital. Im reading it and only found a few minor things, such as that chromosomal mutations are somatic mutations and are not passed on, they only really take place in mitosis at interphase. They can happen during meiosis but it will give rise to a new allele and so genetic variation and if they take place in the egg or sperm, the mutated allele will be present in every cell.

    Also found out that cystic fibrosis transmembrane regulator protein forms the channel that maintains Cl- and water across the membrane, the mutation causes it to be unable to transport the water and Cl- ions and so it means the cilia are dehyrdated and thus cant shift mucus which means mucus build up + infections.

    Wow reading it seemed to work O.O
    Yeah true but you're safer using the actual book.
    My mums been on my case since yesterday, because all I've been doing is writing notes from the book and not actually taking in what I'm writing. She told me to ditch all the note taking and just basically READ the book.
    Like for meiosis as you explained nicely above, read every point and then look at the diagram illustrating the point. There's no need to write everything down. It works aswell, because all I've been doing today is just reading and I remember a whole lot more than I did when just note taking. I suppose once you've read everything through, you can test yourself by writing out..
    Offline

    0
    ReputationRep:
    (Original post by I Have No Imagination)
    Yeah true but you're safer using the actual book.
    My mums been on my case since yesterday, because all I've been doing is writing notes from the book and not actually taking in what I'm writing. She told me to ditch all the note taking and just basically READ the book.
    Like for meiosis as you explained nicely above, read every point and then look at the diagram illustrating the point. There's no need to write everything down. It works aswell, because all I've been doing today is just reading and I remember a whole lot more than I did when just note taking. I suppose once you've read everything through, you can test yourself by writing out..
    Yeah i have the same funnily enough, i write out notes which takes like 2/3 weeks for the whole book (even the rev guide is pretty long for that), yet i dont learn it so it seems like a waste.

    The way i do it, is either test yourself by saying key points out loud and writing it down. Only problem is now fusing the book and the revguide and i should be neigh on done for this part.
    How you getting on?
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    Yeah i have the same funnily enough, i write out notes which takes like 2/3 weeks for the whole book (even the rev guide is pretty long for that), yet i dont learn it so it seems like a waste.

    The way i do it, is either test yourself by saying key points out loud and writing it down. Only problem is now fusing the book and the revguide and i should be neigh on done for this part.
    How you getting on?
    Yeah, testing yourself out loud is a good method. Ermm I'm on genes and body plans at the moment. The spec says ' explain that the genes that control development of body plans are similar in plants, animals and fungi, with reference to homeobox genes' but the book is pretty crap at explaining it..do you have any clue as to what we're supposed to learn about this homeobox nonsense?
    Offline

    1
    ReputationRep:
    I always have a copy of the specification in front of me when revising. It's a good guide, so that you're not wasting you're time learning crap you don't need.
    Offline

    0
    ReputationRep:
    (Original post by I Have No Imagination)
    Yeah, testing yourself out loud is a good method. Ermm I'm on genes and body plans at the moment. The spec says ' explain that the genes that control development of body plans are similar in plants, animals and fungi, with reference to homeobox genes' but the book is pretty crap at explaining it..do you have any clue as to what we're supposed to learn about this homeobox nonsense?
    Yeah, rev guide is good for this bit (more than the book anyway).

    Basically, homeotic genes are the 'master' control genes for development.
    Proteins code for body plans which are used to develop the body and so you can control the development using proteins by affecting rate of transcription.

    Homeotic genes are found in homeobox clusters (so u can also call homeotic genes, homeobox genes). These clusters can code for proteins that move furthur along DNA and bind to specific genes which act as transcription factors (i.e. activating the gene causing its expression or repress it so its no longer produced).

    In addition to this you have another two types we need to know, maternal effect genes - those that determine the polarity of an embryo (e.g. which part is the head and which is the end/rear) and then segmentation genes - these determine the polarity of each segment which is set out in the body plan (i also think that it works in telling things where to grow in that segment as a result e.g. in drosphilia, they have a few segments, these determines whhich segment limbs and legs grow etc).

    In all organisms, these homeotic genes are similar, a good way to demostrate this is if u transfer homeotic genes from one organism to another, the organism produced will still be the same as the organism youve donated it to. Because they act in a similar way and therefore can be activated in the same way in different organisms.
    I think that should cover it.
    Offline

    9
    ReputationRep:
    (Original post by ibysaiyan)
    There ya go
    http://www.ibymegaupload.com/showthr...6-Bio-Jan-2010
    Thanks :-) but I can't seem to make it work... I keep getting a page saying 'database error'. Will try again later...
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    Yeah, rev guide is good for this bit (more than the book anyway).

    Basically, homeotic genes are the 'master' control genes for development.
    Proteins code for body plans which are used to develop the body and so you can control the development using proteins by affecting rate of transcription.

    Homeotic genes are found in homeobox clusters (so u can also call homeotic genes, homeobox genes). These clusters can code for proteins that move furthur along DNA and bind to specific genes which act as transcription factors (i.e. activating the gene causing its expression or repress it so its no longer produced).

    In addition to this you have another two types we need to know, maternal effect genes - those that determine the polarity of an embryo (e.g. which part is the head and which is the end/rear) and then segmentation genes - these determine the polarity of each segment which is set out in the body plan (i also think that it works in telling things where to grow in that segment as a result e.g. in drosphilia, they have a few segments, these determines whhich segment limbs and legs grow etc).

    I think that should cover it.
    Ooh, good explanation, thank you. This is in the how science works bit, so there's a good chance they'll ask something on it?
    Offline

    0
    ReputationRep:
    (Original post by I Have No Imagination)
    Ooh, good explanation, thank you. This is in the how science works bit, so there's a good chance they'll ask something on it?

    Maybe, im a bit suspicious that were going to get asked on vitamins, because theres a mention on many pages/spreads about them.

    Oh btw, vitamin A (retinol i think?), an excess of this causes activation of some homeotic genes when an embryo is in development and so messes around with the body plan, so its good to avoid this when a woman is pregnant else it can cause birth defects.
    Offline

    1
    ReputationRep:
    Ah i find the plant growth hormones stuff excruiatingly boring =/
    Offline

    12
    ReputationRep:
    (Original post by Falcon91)
    Maybe, im a bit suspicious that were going to get asked on vitamins, because theres a mention on many pages/spreads about them.

    Oh btw, vitamin A (retinol i think?), an excess of this causes activation of some homeotic genes when an embryo is in development and so messes around with the body plan, so its good to avoid this when a woman is pregnant else it can cause birth defects.
    Oh yeah thanks, I forgot about this.
 
 
 
Poll
Which accompaniment is best?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.