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122

Biological examples similar to programming statements: IF : Transcriptional activator; when present a gene will be transcribed. In general there is no termination of events unless the signal is gone; the program ends only with the death of the cell. So the IF statement is always a part of a loop. WHILE : Transcriptional repressor; gene will be transcribed ...


99

The Felis catus genome has been published, annotated, and updated quite a bit since 1996, including spans of so-called intergenic regions, which are basically scaffolding and other structures, along with perhaps some unidentified genes, pseudogenes, regulatory sequences, etc. Basically, pretty much the entire DNA sequence is available now, not just the gene ...


61

While Matt's answer is perfectly correct, it is important to note that the sequence $(CAT)_n$ in DNA is not restricted to cats, and you would expect to find it anywhere. For example, searching the human genome for the same 3-tandem repeat CAT sequence results in many hits as well. This is because you are essentially searching for short tandem repeats on ...


42

This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed. Long Story Short Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" ...


28

Chart of C-values (the mass of DNA in a single haploid cell); there is no logical order to the groups: [source] Base pairs in haploid genome (some examples): Escherichia coli (bacterium): ~4.5 million Caenorhabditis elegans (nematode worm): ~100 million Homo sapiens (we all know what these are): ~3 billion Pinus taeda (coniferous tree): ~22 billion ...


26

The image was not in the DNA as such, only as an abstract representation that could be converted into an image from knowledge of the code. Briefly, they encoded the image into DNA, using a couple of different strategies in which DNA represented pixels -- either with a single DNA base representing a pixel, or with a triplet representing a pixel. Knowing the ...


26

Are there examples of cells with more than one nucleus? Yes, they are called Multinucleate cells. There are two types of multinucleated cells Syncytia Coenocytes I highly recommend having a look at this answer for the definitions. Examples of Syncytia include Osteoclasts Skeletal muscle fibers (thanks @kmm) Examples of Coenocytes include Codium (...


24

The uniqueness of irises and fingerprints are, as you said, limited to the number of possible permutations of irises and fingerprints. A similar problem exists in computer science, and is known as a hash collision. Given sufficient samples, there will always be a collision for a hash of finite size. However, the sample space is sufficiently large for iris ...


23

One must always be careful not to stretch an analogy further than it can withstand, but since you started these analogies, I will follow up on them and explain the small mistake you've done in their representations. The two books are not as different as you have in mind. You are not pasting the beginning of Uncle Tom's Cabin with the ending of Harry Potter ...


22

So, a quick molecular biology lesson. Proteins are the things that make up a good percentage of our cells (which make up a good percentage of us), and are the things that do the work of the cells - many are catalysts and are known as "enzymes". Proteins are encoded by genes - while the statement that one gene codes for one protein is not quite correct (...


22

The 5' and 3' mean "five prime" and "three prime", which indicate the carbon numbers in the DNA's sugar backbone. The 5' carbon has a phosphate group attached to it and the 3' carbon a hydroxyl (-OH) group. This asymmetry gives a DNA strand a "direction". For example, DNA polymerase works in a 5' -> 3' direction, that is, it adds nucleotides to the 3' end of ...


20

Neandertal DNA has been completely sequenced multiple times now, using DNA from bone and tooth samples found in cool or cold environments. The first Neanderthal genome sequence was described in 2010: A Draft Sequence of the Neandertal Genome Since then, as well as higher-quality sequence, more genomes have been completed; at least 6 individuals have been ...


19

There are certainly some comparisons that could be made between the way genes are expressed from DNA and logic functions, but they aren't great. But synthetic Biology is really a blossoming new field that is attempting to integrate logic functions into biology, see e.g. Siuti et al (2013). The above paper is a brilliant example of a group using bacteria to ...


19

Actually, no. There are also recombination prone regions of the Y chromosome that recombine and exchange material with X chromosomes, and these are called pseudoautosomal regions (PARs). Y chromosomes can be used similarly to mitochondrial DNA to build up profiles of ancestry, but the sequences used for this purpose lie outside PARs, in the non-recombining ...


19

Well, the oldest intact DNA found is actually 419 million years old, and it belongs to (not surprisingly) bacteria. Samples were extracted from surface-sterilized salt of different geological ages (23, 121, 419 million years of age, MYA). But as you mentioned, these are fragments. Studies on the half-life of DNA suggest that even under ideal circumstances, ...


19

Hmm, I think that the teacher is actually correct and that the previous explanation, although very nicely referring to text book diagrams, is a little misleading. The issue here is the nature of a hydrogen bond within the DNA structure. Within a chemical context, generally a molecule is a collection of atoms primarily bonded together via covalent bonds. ...


18

To quickly answer your question, yes DNA changes over the life time of many organisms including humans. You have a whole host of mechanisms in your body that try to prevent your DNA from changing, but they are not perfect. A good example of this is DNA degradation due to aging. When discussing aging in biology, we use the technical term senescence. Of ...


18

First off, that paper is the seminal discovery and publication of the structure of DNA, and is absolutely worth the read. It's one of the most important pieces of scientific literature. The short answer is no. DNA stands for Deoxyribonucleic Acid. The long answer is... this is really just picking at nits.1 DNA, deoxyribonucleic acid, is a type of ...


17

Since it was my edit of your question that started all this, I may as well weigh in. I will give a simplified version of genes and gene transcription, there are various details that make the process much more complicated than what I will describe but they are not relevant to the basic question here. First of all, as others have mentioned, genes are specific ...


17

There is no difference in base pairing between different kinds of organisms. Humans, animals and bacteria all share the same fundamental mechanisms as they all use DNA. Which bases can pair is determined by the chemistry of the individual bases. The bases in DNA form the following hydrogen bonds when they are paired: If you would try to combine other bases ...


17

Nice question which leads to the fundamentals of DNA and RNA. DNA (Deoxyribonucleic acid) is the core of life in Earth, every known living organism is using DNA as their genetic backbone. DNA is so precious and vital to eukaryotes that its kept packaged in cell nucleus, its being copied but never removed because it never leaves the safety of nucleus. DNA ...


17

I will try to answer the question in the title: how can we know the sites where DNA binding proteins bind? I'll explain two experimental methods to identify binding sites on DNA. DNase footprinting ChIP-seq (Chromatin Immuno-Precipitation with sequencing) DNase footprinting We can locate proteins bound to DNA by their ability to protect DNA from some ...


17

DNA is not analogous to computer code which renders your search for similar constructs in it meaningless. To give a couple of simple examples why this is: Computer code has a sequential order of execution; DNA acts in parallel and out of sequence, it is not "executed". Computer code has a strict and consistent meaning so the line if x==4 : x=7 always does ...


17

Strictly speaking, all nucleated (eukaryotic) cells contain linear DNA. In addition to the nucleus, the mitochondria (which break down food molecules and create chemical energy) and chloroplasts (which facilitate photosynthesis) also have small stores of their own DNA and this DNA is circular. This adds weight to the hypothesis that these organelles were ...


17

In addition to Remi.b's answer, it should be noted that the phage Phi X 174 is the only organism in your list which significantly deviates from Chargaff's Rule (by more than 1-2 percentage points for the A-T pair). While sampling errors are indeed more likely in organisms with small genomes, there is in fact another factor in play here. This is because ...


17

Just to add what might have been missing in the beautiful answer by @iayork. I just want to give a more simple picture of the encoding done in the E. coli DNA. First for the rigid strategy in which 4 pixel colors were each specified by a different base, suppose we have a sequence: AAGCCCTGGTCAGCT Ignore the first AAG and start with C. Now, each base of ...


16

In my opinion, Prof. Allen Gathman's "great 10-minutes video on Youtube" is a pretty waste of time if you already know how hydrolysis happens. In fact, he has not considered the 3'->5' route in an unbiased manner; he doesn't seem to look at the possibility of a triphosphate appearing at the growing 5' tip of the strand in the 3'->5' case. Actually, the ...


16

This language is called the genetic code. But before talking about this specific code, it is important to talk about how the code is read. Please note that the below answer is a simplification of the reality. Mechanism by which the code is read To make things easier (reality is a little more complicated), DNA is "formatted" into RNA which is then "...


16

To augment the other answers, let's compute the probability of CATCATCATCAT occurring in random DNA sequence. Cat DNA length is 2.7 gigabases (source), and there are 4 possible bases. For 1 CAT there are 3 bases, giving expected number of occurrences in 2.7 Gb as $\frac{2.7 \cdot 10^9}{4^3} \approx 42\,188\,000$ Repeating the calculation for longer ...


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