Chelleee Posted February 10, 2009 Report Share Posted February 10, 2009 hey!help is much appreciated considering i'm about to go berserk over this:heres my dilemmaits about meiosis~first of all, do BOTH homologous pairs cross over or only the uhh larger one? one of my textbooks only shows the larger one, the powerpoint that my teacher showed us shows both, my OTHER textbook shows NONE and my OTHER OTHER textbook starts off with 2 chromosomes for meiosis @_______________@secondly!do the cells split in two after telophase 1? or do they remained joined? and then fully split after telophase II into 4 different cellsIF they do split into two, why is it called telophase and why is the cell beginning to divide in anaphase (according to one of the diagrams anyway)? shouldn't it be called cytokinesis? @-@ or is there cytokinesis I & IIargh i'm so confused Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted February 10, 2009 Author Report Share Posted February 10, 2009 (edited) *TOPIC 4 (4.2)---MEIOSIS*Alrighty Alrighty calm down. OK, so, you have 2 homologous pairs in the parent cell. The cross over is in Prophase 1.a homologous pair has 2 sister chromatids.In crossing over, one sister chromatid from the 1st pair and another from the second pair form chiasmata, which means that a DNA of one if connected to the other.The other other two(one from each) remain as they are.Cell splits in two after Telophase 1 and then each one splits into two in telopahse 2/cytokinesis.The cell doesnt split in neither of the anaphases. Anaphase 1 is the stage where the cell is getting ready to split into two. Anaphase 2 is the same thing, but its where the two divided parts are getting ready to divide again.Telophase vs. cytokinesis:Cytokinesis is the process where the cell literally splits into two by the membrane being split into two. It is put within telophase, its not a phase on its own.Telophase is where : 1)nuclear membrane forms 2)chromosome going to normale size 3)cytokinesis happens.Anything else? Edited March 31, 2012 by Mahuta ♥ 2 Reply Link to post Share on other sites More sharing options...
IBdoc Posted February 10, 2009 Report Share Posted February 10, 2009 We have always seperated cytokinesis from telophase and we put in it in one of the three steps of the cell cycle: Interphase, mitosis, cytokinesis. Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted February 10, 2009 Author Report Share Posted February 10, 2009 Hows that? Please explain.Because cytokinesis is a process not a phase. Just like endocytosis and exocytosis. What is a fact is that cytokinesis is not really a phase as much as its a process.As for the IB Bio Syllabus, doesnt make much of a difference as long as you know what it means and mention it in your answer.I personally was told what I said. But Im interested in knowing about your comment. Please Reply Link to post Share on other sites More sharing options...
Chelleee Posted February 11, 2009 Report Share Posted February 11, 2009 (edited) Alrighty Alrighty calm down. OK, so, you have 2 homologous pairs in the parent cell. The cross over is in Prophase 1.a homologous pair has 2 sister chromatids.In crossing over, one sister chromatid from the 1st pair and another from the second pair form chiasmata, which means that a DNA of one if connected to the other.The other other two(one from each) remain as they are.Cell splits in two after Telophase 1 and then each one splits into two in telopahse 2/cytokinesis.The cell doesnt split in neither of the anaphases. Anaphase 1 is the stage where the cell is getting ready to split into two. Anaphase 2 is the same thing, but its where the two divided parts are getting ready to divide again.Telophase vs. cytokinesis:Cytokinesis is the process where the cell literally splits into two by the membrane being split into two. It is put within telophase, its not a phase on its own.Telophase is where : 1)nuclear membrane forms 2)chromosome going to normale size 3)cytokinesis happens.Anything else?oh wow, it's beginning to make sense now.i'd always assumed cytokinesis was a stage of its own because of the way we learnt it: inter, pro, meta, ana, telo, CYTOKINESISand it always had its own little label and everything >____> well at least now i've got that clarified!thank you soo much, if i get full marks for meiosis on the mock exams this term, you'll definitely get majority of the credit xP EDIT: ok i'm back with another question on meiosis, prophase is the phase when the DNA duplicates correct? so why do they call it "prophase II - after the first division (telophase I) -" even though technically the chromosomes don't duplicate?!this naming is getting on my nerves as well as the major differences between my textbooks. thanks again *sigh~ Edited February 11, 2009 by Chelleee Reply Link to post Share on other sites More sharing options...
IBdoc Posted February 12, 2009 Report Share Posted February 12, 2009 Cytokinesis is not a phase of mitosis or meosis but it is part of the cell cycle which is divided into interphase, mitosis/meosis, cytokinesis. In telophase, the last thing that happens is the constriction of the cell membrane for an animal cell. Cytokinesis happens just after mitosis when the two cells divide completely. It is indeed a process just like mitosis is a process by which the nucleus divides to form two identical nuclei. Our teacher told us that there has been a lot of debate about this and some say that cytokinesis happens in late telophase but as you said, in doesn't really make a diffenrence for IB as long as you know what it means. Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted February 12, 2009 Author Report Share Posted February 12, 2009 Yes, exactly spot on That was my point so chelleee, Cytokinesis isnt a stage of meiosis nor mitosis.Thanks for the clarification IBdoc Reply Link to post Share on other sites More sharing options...
*Sternchen* Posted February 15, 2009 Report Share Posted February 15, 2009 I also need help! I hate doing labs but we have to design a lab and it has to be on behavior of invertebrates. i already thought of a research question: Can the woodlice remember the way out of a maze when a reward is given to them at the end? but i dont know what my variables are. my dependent variable is how many errors the woodlice make until they find the reward, but what's my independent variable? because i just let the woodlouse enter the maze and count the error it makes without giving it the reward. and then í'm gonna count the errors it makes when it gets a reward. I hope somebody can help me, because i really suck at biology. Reply Link to post Share on other sites More sharing options...
moneyfaery Posted February 15, 2009 Report Share Posted February 15, 2009 You should be speaking to your teacher if you run into problems on your IAs. We can't help, sorry. Reply Link to post Share on other sites More sharing options...
*Sternchen* Posted February 16, 2009 Report Share Posted February 16, 2009 You should be speaking to your teacher if you run into problems on your IAs. We can't help, sorry. i did speak to him and i was going to speak to him on friday but i was sick. anyway i thought about it again and i changed my research question. so now i know my variables. Reply Link to post Share on other sites More sharing options...
dexter Posted February 25, 2009 Report Share Posted February 25, 2009 I dont understand Mitosis .... Lol Reply Link to post Share on other sites More sharing options...
HJ:) Posted February 28, 2009 Report Share Posted February 28, 2009 Um can you explain the enzyme inhibition? I don't get it Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted February 28, 2009 Author Report Share Posted February 28, 2009 (edited) *TOPIC 7 (7.6)---Enzymes and enzyme inhibition*Enzyme inhibition:1) Competitive inhibition:Competitive inhibition is the type of inhibition where the inhibitor inhibits/takes over the active site. It is competing for the active site.To be able to compete for the active site, the inhibitor has to be similar, chemically, to the substrate.Since the inhibition is due to the competition over active site, the higher the concentration of the substrate, the lower the effect of the inhibitor. Because there is less chance of the inhibitor taking over the active site.2)Incompetitive inhibition: Incompetitive inhibition as the name suggests, is the type of inhibition where the inhibitor is not competing for the active site.The only thing that this inhibitor does is that it binds to another site, not the active site but the allosteric site. Binding to the allosteric site causes a change in the shape of the active site. A change in shape of the active site stops the substrate from binding to the active site.The problem with this is, that even if you increase the concentration of the substrate, the inhibitor will still have the effect as its not a matter of 'competition'.Since this inhibitor is not competing for the active site, it doesn't have to have a similar structure, thus, the incompetitve inhibitor is not chemically similar to the substrate.3) End product inhibition:This could be put under incompetitve inhibition.When you have a metabolic pathway, whether cyclical or non-cyclical.This is when the last product inhibits the enzyme that catalyzes the first reaction at the allosteric site.The significance of this inhibition is to stop the build-up of the products if there is too much of it. This is an example of negative feedback.Anything else? I'm not sure I explained the last one properly, so if there's anything unclear, please tell me. Edited March 30, 2012 by Mahuta ♥ 1 Reply Link to post Share on other sites More sharing options...
IBdoc Posted February 28, 2009 Report Share Posted February 28, 2009 (edited) I dont understand Mitosis .... LolOh come on. You have a 7 in biology and you don't understand mitosis? It doesn't sound right. Anw, the explanation given above is clear I think but if you still don't get it try this website: http://www.click4biology.info/c4b/2/cell2.5.htm Edited February 28, 2009 by IBdoc Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted February 28, 2009 Author Report Share Posted February 28, 2009 LOL, i must say IBdoc, i agree. Ahmed..what were you thinking I havent really explained mitosis, but it is like..the first half of meiosis, lol, almost. Reply Link to post Share on other sites More sharing options...
HJ:) Posted February 28, 2009 Report Share Posted February 28, 2009 (edited) Ahmad, she knows your name~! Like OMG ! LOL Edited February 28, 2009 by HJ:) Reply Link to post Share on other sites More sharing options...
HJ:) Posted March 29, 2009 Report Share Posted March 29, 2009 I don't have a clue on what is Gram positive and Gram negative is. can anyone explain it to me??? Reply Link to post Share on other sites More sharing options...
Sandwich Posted March 29, 2009 Report Share Posted March 29, 2009 You mean +/- 0.1g type of thing?It's an error marker and tells you how accurate the reading is. So like if you had measured out 33.05 grams, +/-0.01g would tell you that the machine you measured it with is accurate to within plus or minus an extra 0.01g. i.e. your measurement could either be correct, plus one 0.01g (33.06) or minus 0.01g (33.04). The machine isn't 100% sure, so it's giving you an idea of the sort of range it could be out by. 1 Reply Link to post Share on other sites More sharing options...
HJ:) Posted March 29, 2009 Report Share Posted March 29, 2009 um.. no. Gram positive and Gram negative Eubacteria 1 Reply Link to post Share on other sites More sharing options...
Mahuta ♥ Posted March 29, 2009 Author Report Share Posted March 29, 2009 LOL, no Alice, thats something in bacteria.*OPTION F (F.1.7)---GRAM +VE and GRAM -VE eubacterial cell wall*HJ, gram positive and gram negative are one way you could distinguish between eubacteria.Gram +ve and gram -ve are two different types of cells walls.Gram +ve:The reason its called this, is that its structure allows it to be stained with purple by the Gram stain. The thing that stains is the peptidoglycan. So this type of eubacteria has a thick peptidoglycan layer.Gram -ve:This means that it is stained less by the gram stain, so the color red is visible instead. Therefore, this eubacteria has a gram -ve cell wall because it has a thin peptidoglycan layer.Thats all you have to know about Gram +ve and -ve. Reply Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.