biol+4+faq+(nsfaq)

If you have any questions or are uncertain about anything to do with the course, then this is the place to get help. I will try and respond to your query as soon as possible, although I strongly encourage you all to try and answer each others questions first.

Q. How does the membrane of the nucleus remain semi permeable if it does not have a complete membrane, instead having pores? Can't other unwanted substances travel in or out through these pores apart from mRNA molecules? // A. interesting question and i probably don't enough about it to give you a full account. but you are right in saying that other substances can go through. same rules of movement apply at the nuclear pore in that only water soluble substances tend to pass throguh, diffusion of small molecules will occur, being a pore, larger substances could pass through as well, but the key thing is that nuclear pores are protein complexes and it therefore can regulate water soluble substances (particualrly larger ones such as proteins) VM //

This question is to do with the homologous pairs - i'm a bit confused about their meaning. You said something about each chromosome coming from a different parent yet they are identical in some way. How does this work? If each chromosome is from a different parent, there must be a different DNA in it thus not being similar at all... // A. You're latter point is spot on. Homologous chromsomes are not identical in relation to their DNA base sequence. I would never have said this. They do however contain the same genes in the same position. But genes can have different forms called alleles which we will look at next term in more detail. VM //

Q. Is the second part of meiosis a mitotic division and are there any differences if so? // A. Yes the second stage is pretty much what happens in mitosis, ie the sister chromatids are pulled apart from each other. This is the main point. VM //

Q. How come interphase is not 'technically' a part of meiosis/mitosis? // A. Well, if you have a look at the life cycle of a cell, it can be broken up into two overall parts. The part when it isn't dividing (INTERPHASE) and the part when it is. Based on this, a cell is either in interphase OR it is undergoing cell division. It's that black and white. VM //

Q. Can you please explain to me what introns and exons are and why they get cut out? // A. When an mRNA molecule is transcribed from the DNA that makes up a gene, not all of the base sequence in this preliminary mRNA is used for translation, so some bits get cut out (called introns). The remaining bits (called exons) make up the mature mRNA and it is this bit that goes to a ribosome to be translated into a chain of amino acids. Why? Well, this is a long story really and you do not need to really understand this. But one thing that can happen is that the same gene can result in different polypeptides because the mRNA can be "spliced" in different ways to produce different mature mRNAs. VM //

Q. Somehow, I decided to venture over to the wikispace 2008 page, and had a look at the SAC criterion for their evolution SAC. Can I assume (never assume) that that information is a good starting point to begin revising for the upcoming SAC even if those dotpoints will not necessarily be used on OUR SAC? (That was far more complicated than it needed to be. Trust that i would go the round-a-bout way of asking questions) // A. First of all, as this question relates to the SAC I will post it on the evolution SAC page as well. Yes, good idea to use those dot points as a start. As it turns out I will hand out last year's SAC in Sunday's session for you to do for H/W. VM //

Q. I noticed on the SAC page for evolution you wrote a conclusion is not a description of the results. I actually thought that is exactly what a conclusion is. We talked about this briefly in our sac debreif but can you verify again, what is the conclusion supposed to include? (Please don't say an explanation of why the results are what they are. this is exactly what i thought it was not) Joshua (Miles Davis) Appelboom A. // A conclusion is neither of the things you mentioned above. It is a statement that you can make based on the results. It is not an explanation nor a description of the results. VM //

Q. Why is it that women only produce one haploid gamete and three haploid degenerate gametes? (I'm sure this is quite an important concept to grasp, but as you are well-aware, meiosis and mitosis aren't exactly what I have a knack for). So please help Vojtej... // A. First of all, you do not really need to know about the detail involved in oogenesis (production of ovum). It is quite complicated and involves meiosis halting for a period of time (during embryonic development) before recommencing later in life to produce the final ova. So, it is different to that of spermatogenesis (production of male gametes) but the bottom line is the same, meiosis is involved and as a result haploid cells are produced. That is all that matters. VM //

// Q. Do we need to know about lethal genes? I know you taught us this concept but its not in the study design as far as i can see. A. Yes. The key is that you are able to recognise from the information given in a question that it involves a lethal gene. VM //

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