So apparently there is some sort of mini revolution going on in the understanding of the precise role of RNA in the cell, or something---I keep reading these articles in Nature which claim that the field of molecular biology is changing or will change pretty dramatically. Unfortunately, I don't really remember anything from tenth grade biology, and I took a graduate level Quantum Chemistry class to get out of having to take Biochemistry as an undergrad. So, to the initiated, who are willing: teach me. Of course, you can also tell me to get lost and go read Wikipedia, but I'd rather be involved in a conversation where I can ask questions (mostly stupid and naive one) because this is how I learn most effectively.
I’m not telling you to get lost, Please Register or Log in to view the hidden image! but IMO the best thing you can do to learn all about DNA (and RNA) is go to DNA from the Beginning, a fantastic online tutorial from Cold Spring Harbor Laboratory. It is a comprehensive teaching aid that will take you from the basics through to more complex subject matter. You may remember that there are three main types of RNA – ribosomal RNA (rRNA), transfer RNA (tRNA) and messenger RNA (mRNA). The tutorial will introduce these molecules and describe their functions. Very broadly speaking, the revolution in molecular biology that you are hearing about concerns the role of other types of RNA: small nuclear RNAs (snRNA), in particular micro RNAs (miRNA) and short inferring RNAs (siRNA). It was discovered only recently that cells contain a large population of very small RNA molecules in the order of ~22 nucleotides in length. Then it was discovered that they bind to mRNA and either prevent it from being translated into a polypeptide or cause the degradation of the mRNA. This represents a whole new level of gene regulation that was totally unknown until only a short while ago. Please Register or Log in to view the hidden image! In the last few years it has been discovered that the expression of a large percentage of the genes in the eukaryotic genome is controlled by miRNAs, including many key developmental genes. miRNA has also been shown to be intimately involved in disease progression, such as various cancers. This has led to a rapidly increasing effort to develop snRNAs and snRNA interacting molecules as a new class of therapeutic drugs. Indeed, siRNA is already being used to treat a type of macular degeneration.
Hi Hercules--- The link you gave me is very good (if a bit catoonish). They seem to jump into terminology, though: 1.) What is "F1 generation"? 2.) What is "allele"?
Well, since I just saw this thread by chance (in recent times I tend to steer clear of the bilogy section) I thought I may as well butt in. 1) F1 referst to the first filial offspring generation, orginating from the crossing of two parental lines. F2 would be their offspring, etc. 2) Alleles refer to variations on a specific locus (position) in a genome. For instances, variations of a single gene could be different alleles. Homozygous refers to having identical alleles on all chromosomes. Heterozygous means that one the same position on different chromosomes there are different alleles (that is, the sequence is not identical there). Ow and the mentioned revolution refers to additional roles that have been found for RNA beside being structural in ribosomes or its involvement as template in proteinbiosynthesis. Especially their regulatory functions (sRNAs/riboswitches) or (limited) enyzmatic ones (ribozymes).
Sorry Hercules, for trampling a bit over your explanation of sRNAs, I only thought that for Ben something more general would be more helpful as a starting point. I am kind of used to talking to physicists about biology by now, and I found that you have to start really basic. Just to be on the sure side (no offense intended). On the other hand the physicist (sadly mostly rightfully) claim that biologist have no understanding of maths and hence they are unable to understand biology either (which I obviously cannot subscribe to).
A zygote is the fused haploid gametes in sexually reproduction. A zygote is diploid. So the terminology hetero/homozygous in genetic terms is which gamete (the male or female) provides the dominant genes - the distribution of gene alleles. But that's Mendelian. A homozygote is an identical twin, too, and a heterozygote is a twin from two different eggs.
Here are some resources for you that will help you: UC Berkeley Webcasts of General Biology Classes: General Biology 1A And a great site for genetics basics: http://learn.genetics.utah.edu/ Also, swing by a used book store and grab a good (fairly recent) genetics text. Enjoy!
Yes Please Register or Log in to view the hidden image! Note that we would say the same about you guys, too. It's been my experience that the key to any field is understanding the terminology. That being said, I guess I need to see the big picture first. The link Hercules sent me IS a good reference, but it's maybe a little TOO pedagogical. And I have no idea what the above means. I'm not sure what a "genome" is. How many genomes do I have? Just one? (I seem to recall the "Human Genome Project".) Is a genome a collection of a bunch of genes in some specific order? What's it made out of? Where does it live? what do genomes have to do with DNA? Can I look at a genome under a microscope, or is it a more abstract term for a bunch of disjoint genetic goo floating around in my body somewhere? You guys have to understand---I slept through biology in the tenth grade, which is the last time I saw any of this stuff. I will continue with the tutorial that Hercules provided, and will continue to have stupid questions, for anyone who is listening.
Genome is the full set of chromosomes in a gamete [male or female cell]. Since we are a diploid organism [XX or XY] we have two full sets in each somatic or diploid cell. Hence we have 23 pairs or 46 chromosomes. As for the relationship between genome and DNA, a picture may be more helpful Please Register or Log in to view the hidden image! Since we have a set of chromosomes from each parent, the chromosomes may have an alternate form of the gene at the same loci or location on either set, these are called alleles Please Register or Log in to view the hidden image! When alleles are similar, they are homozygous, when different, they are heterozygous. They may be similar for a dominant trait [eg brown eyes] or a recessive trait [eg blue eyes]. Or they may be heterozygous in which case the dominant trait will be expressed.
That goes without saying. I only mentioned that because I have been working with biophysicist for quite a while now. And misconceptions tend to pop up. Mostly the students are a bit complicated to deal with, because they do not acknowledge that different fields often require a slightly different view on things (e.g. the fact cells are overall less deterministic than most closed systems). But I also had a hard time to get back into physics and see where I can apply it to biology meaningfully. Precisely. Regarding "Genome". Traditionally the genome is simply the complete set of genetic information of an individual, more precisely it refers to the complete DNA of a cell. This includes chromosomes as well as any other extrachromosomal DNA. For the details you need to know one thing first. There are essentially two basic typs of cells. Pro-and eukaryotic cells. Prokaryotic cells are bacteria or archaea whose DNA is not organised in a compartment. The "main" DNA, the chromosome, just sits in the cell bound to parts of the cell membrane. They often do have additional DNA carrying genetic information that are floating in the cell. Both tend to be circular, but it is not always the case. In Eukaryotes DNA is organised into a nucleus and only in them will you find the highly organised chromsomes (looking like an X under the microscope). Again a genome is just the complete genetic material of a cell. I will get back for the rest when I got time.
And Ben, don't overlook that the RNA that makes up the ribosomes will also be of two different categories. Ribosomes that translate for the nucleus; and ribosomes that translate for the organelles [mitochondria, chloroplasts]. The mitochondrial ribosomal RNA is very similar to that of bacterial ribosomal RNA, and believed derived from it. But that gets into evolution of organelles, which itself will be too highly involved for discussion here. It gets ever more fascinating, and far more complex and difficult to understand than physics.
Yes. All bacteria and archaea are prokaryotic, all others are eukaryotic. It is a taxonomic distinction, as much as a descriptive one. We are all eukryotes, from fungi, protozoa plants animals, etc.
Most likely they were, but they are not self considered self-sufficient cells anymore, but part of the eukaryotic cell (as an organelle).
