DNA Okay, a little intro on DNA. The full name for DNA is deoxyribonucleic acid. What is it? Not exactly sure, but we can picture a long helix thing that looks like a twisted ladder, like the ones we see on TV, and we can assume its what makes us uniquely us (physical features, personality, etc). What I do know for now is that its primary function is to store and transmit info that tells cells how and when to make proteins. The proteins in return, form the structural units of the cell and controls its chemical processes. Structure of DNA The nucleic acid DNA is an organic compound. It is made of sub-units called nucleotides-a chemical compound composed of 3 things-one or more phosphate groups, a sugar, and phosphate group. (A/N I tried Googling an image to find exactly- which part of DNA the NT-yeah, pretty stupid- is but alas, all I get is chemical compounds pics in simple hexagonal form. Sigh. So what if I only looked in the first two pages) All I know is that each DNA molecule consists of two long nucleotide chains. The specific structure of a DNA molecule is the sugar deoxyribose, a phosphate group consisting of phosphorus atom surrounded by oxygen atom, and a nitrogen containing base so called coz it contains nitrogen.
The sugar and phosphate are identical in all DNA nucleotides, but the other part can consist of 4 different kinds. The 4 different nitrogen containing base found in DNA are adenine, thymine, cytosine, and guanine. Adenine and Guanine have two rings of carbon and nitrogen, while thymine and cytosine only have one ring. Bases with two rings such as A and G are called Purines. Bases with one ring like T n C are called Pyrimidines. The Double Helix In 1953 these two mad scientist named James and Francis suggested a model of the DNA structure. This model proposed that DNA is two long chains of nucleotides spiraling around eachother like a spiral ladder. Anyone who watches a good amount of TV can picture this. This form be calleth the Double Helix of Doom. James and Francis relied on info by other scientists to construct their model. Especially on some x-ray pics of something called DNA crystals taken and studied by two other fellow mad scientists Rosalind and Maurice.
Their vile DNA model provided some explanation on how DNA copies itself and how genetic info is stored in cell. In 1962, the cursed model won their awful create-ors, James, Francis, and Maurice the Nobel Award in Medicine for their work. Poor ol Rosalind wasnt recognized coz he died a few years back. Those selfless bastards. So uh, the structure. The FORM. Kay, individual nucleotides are connect by covalent bonds between the sugar and the phosphate group, forming some sort of backbone for the nitrogen-containing base to attach to. Another nucleotide comes and joins lonely nucleotide, they connect through hydrogen bonds with the nitrogen containing bases, which face toward center, of each nucleotide. Behind each NCB is the phosphate and sugar perpendicular to it, just to note.
So theyre connected through hydrogen bonds. The hydrogen bonds that form between the bases in DNA form between a hydrogen atom and either an oxygen or a nitrogen atom. as the textbook sez. Each pair of bases are at uniform length coz in each case one base is purine and the other is pyrimidine. The form is found in many living organisms has a right-hand twist and each turn has like 10 base pairs *holds up nine fingers*. Complementary Base Pairings *yawn* Theres a rule on base pairing called base-pairing rules (didnt see that one coming). Fortunately for me and other simple-minded and/or paper ball-spitting biology student, these rules are easier than ukes *brickd*. CYTOSINE PAIRS WITH GUANINE, THYMINE PAIRS ADENINE. Cytosine/Guanine, Thymine/Adenine. A/T, C/G, J/D slashy goodnessscratch that last part. But these scientific pairings are called Complementary Base Pairings. As we know they attach through hydrogen bonding, but C/G form 3 hydrogen bonds, and A/T form 2. The nucleotide sequence in one chain is an exact complement of the nucleotide sequence in the other chain.
The complementary nucleotide chain in the model led to suggestions on how DNA might copy itself. The process of self cloning is important. Only in this case coz some dividing cells to pass an exact copy of DNA to its offspring. Replication of DNA DNA clones. Replication its called. This is done by the nucleotide chains unwinding, with each chain serving as a template for a new nucleotide chain. Step by step 1. Separation of nucleotide chains. The point at which the chains separate is called the replication fork. The chains are separated by an enzymes called helicases by breaking the hydrogen bonds. 2. Construction of new nucleotide chain. Another enzyme called DNA Polymerases comes along and attaches on each single strand, then starts build up new chains of DNA using nucleotides from surrounding mediums that are complementary to the existing DNA chains, sez here Mr. High n Heavy Biology Textbook. I say magically out of nowhere.
Okay so that was only two steps. I thought it was gonna be longer The DNA polymerase doesnt necessarily start at one end of the strand and work its way to the other. Actually, the enzymes work simultaneously at many different points on the strands. Why? Coz its faster that way, genius. When replication is complete the cell is now ready to undergo division and make cute little cell babies (hurrah!). Each replicated copy of DNA has one new strand and the other from the original molecule. Accuracy and Repair Suppose something goes wrong and.ONE OF THE BASES DONT COMPLEMENT EACHOTHER ZOMG LOLZ!!11one. Well that would be called a mutation and that could have a serious effect on cells (were probably thinking X-Men here). Well the DNA enzymes go back and proofread and repair any mistakes, reducing the chances of error to 1/billion. This means theres still a chance the body makes an error. And DNA can be damaged through agents like chemicals and UV rays. Because of the continuous review and proofreading going on, mutations are reduced.
Review——— Coz I have a way of instantly forgetting things. We shall commence. 1. What are the main functions of DNA? Ooh, I know I know! Erm, primary function was store and transmit info that directs cell how and when to make protein. Also hold genetic info. And directs cell functionand stuff. 2. Identify the types and locations of covalent bonds and hydrogen bonds in a DNA molecule. Covalent bonds are formed between the sugar and phosphate group, which forms backbone for nitrogen containing base to attach to. Hydrogen bonds are form at each pair of bases between the NCBs. Cytosine and Guanine forms 3 bonds, Adenine and Thymine form 2. 3. List the base pairing rules. Oh boy. Anyone who forgets this should be whacked by a 2×4 on the head and unclot the blood flow of dead brain cells. A/T C/G. That is all. 4. What roles do enzymes play in DNA replication? Replication Fork-holds the point at which the chains unwind.
DNA Polymerase-builds up a new chain of DNA. Other- proofread and repair DNA molecules. 5. How would deoxyribose sugar and phosphate bond look like if purines paired up with purines and pyrimidines with pyrimidines? Oh look at the time! 4:32AM! Time to hit the hay =) Chappie 10-2: RNA! RNA *wakes up 13 hours later* Remember that the nucleotides in DNA molecules are grouped together into genes that contain info to direct Protein Productions Inc. in the cytosol. In eukaryote cells, the genes directing profitable company are in the nucleus, while the nucleic acids and other protein block workers are in the cytosol. One nucleic acid, ribonucleic acid (RNA), holds the responsibility of taking genetic info from the nucleus to the protein synthesis site in the cytosol. Structure of RNA RNA is much like DNA aside from a few differences. For one, the sugar molecule of every RNA nucleotide is ribose, whereas the sugar molecule for DNA is deoxyribose. Notice something? The scientific name for these two are derived from the name of their sugar.
Another difference is that thymine isnt a common base for RNA. In fact, its barely used so its place is taken by Uracil, a nitrogen-containing pyrimidine base, and pairs up with adenine. Types of RNA RNA exists in three types with three different functions: Messenger RNA (mRNA)- This baby carries genetic information from the DNA in the nucleus to the cytosol of a eukaryote cell. Its a bunch of RNA nucleotides in a single uncoiled chain. Like half a DNA molecule. Transfer RNA (tRNA)-Its a single chain of about 80 RNA nucleotides folded into a hairpin shape that binds to specific amino acids. Therere about 45 varieties of them. Not sure what they do. Ribosomal RNA (rRNA)- the most abundant form of RNA, its a single chain of RNA nucleotides (again) in a globular form. Joined by proteins, these make up ribosomes where the protein is made. Transcription One function of RNA is to take genetic info from the nucleus and pass it to the cytosol to produce protein. The process of copying DNA info to RNA is called transaction. Lets take a look at the steps. Maybe they wont be just two this time.
Steps of Transcription 1. RNA polyermase (much like DNA polymerase, for those who havent been skipping) binds to specific regions of DNA called promotahs (x-sp!). Promoters mark the beginning of the DNA chain to be transcribed. In eukaryotes, they mark the beginning of a single gene, but in prokaryotes they can mark several functionally related genes. Once RNA polyermase binds to a promoter, the chains untwirl and one is used as a promoted as a template to be used for transcription. The other one is lost and never seen again.(not really). 2. RNA polyermase attaches to the first DNA nucleotide to be transcribed. From there it starts adding complementary nucleotides to the newly forming RNA molecule, to complement the nucleotides from the DNA molecule. Is this too confusing? Dont lose me here! * Realize that the DNA base sequence determines the base sequence of the RNA. Yknow, adenine pairs with thymine, cynine with guanine? Except that there isnt any thymine in RNA! But theres uracil, so the pairings are adenine/uracil and cynine/guanine.
3. Transcription continues by nucleotide until it reaches a region in the DNA chain called the Termination Signal. Its a specific sequence of nucleotides that marks the end. In eukaryotes it indicates the end of a gene, and indicates the end of functionally related genes in prokaryotes. When its reached this the RNA polyermase releases DNA and newly formed RNA molecule. All 3 types of RNA molecules are transcribed in this process. 3 steps! We beat the last steps byONE! *chicken dance* Products of Transcription The products of transcription are called transcripts, and theyre the 3 different RNAs we mentioned before. Though the info from the DNA is passed to the mRNA, all three RNAs are involved and work in the protein factory at minimum wage. Following transcription, mRNA gets into his cellmobile and drives to work from the nucleus, navigates through the tunnels of the Nuclear Membrane, and enters Protein Productions Inc. where the slave driver forcefully directs his victims through the synthesis of protein. I dont know where Im getting at. Review!—— <4 legs good, 2 legs bad!> 1. Define transcription. List the main steps involved in this process. One=RNA polymerase attaches to promoter that marks DNA. DNA untwirlies. RNA attaches to one chain.
Two= RNA P starts forming new RNA, directed by the nucleotide sequence of the DNA. Three=It finishes. RNA P enzyme unattaches, new RNA is formed, cell rejoices. So transcription is copying of DNA info to RNA to make protein. 2. In what ways does the structure of RNA differ from that of DNA? Thymine is substituted by Uracil in RNA and the sugar molecule in RNA is ribose instead of deoxyribose found in DNA. 3. Describe the structure and function of each of the three types of RNA. mNA=carries genetic info from DNA to cytosol for protein synthesis. A single uncoiled chain. tRNA=a single chain consisting of 60 nucleotides and resembles a hair. Therere about 45 varieties of em. The cursed textbook doesnt say else about it so Google it. 4. List three roles of RNA polymerase in transcription. One=Attaches to promoter. Two=makes new RNA. Three=umm, the last two are very generalized roles, so there. 5. What basic principle ensures that the transcribed TNA molecule is carrying the right genetic message. Enzymes proofread and repair mistakes, right? It said so at the end of the first chapter.
For once I actually answered the last question. YAY for me! Chappie 10-3: Protein Synthesis Now that we know how RNA is transcribed, its time to learn how them 3 types of RNA combine their powers to make PROTEIN mwaha. The amount and kind of proteins produced determine structure and function in a cell. Proteins carry genetic info encoded the organisms DNA. (A/N I have gone through this a couple of times and I find this thing snitch to understand. But thats just me. Try to bear here 😉 Protein Structure and Composition Like DNA and RNA, protein is a polymer (chain of amino monomers). Theyre made of one or more polypeptides (chain of amino acids). The sequence of the amino acids in the polypeptide determines how the poly-thing itself is shaped to bind itself to the protein. The proteins function depends on the ability to bind itself with molecules in the cell; that is, how its shaped by the amino-acid sequence attached to it (think as if the polypeptide attaches and molds the protein.) The Genetic Code During protein synthesis, the mRNA transcript info is translated into a sequence of amino acids.
This correlation of the nucleotide and amino acid sequence is called the genetic code. Its used by most organisms to translate mRNA transcripts to protein. The genetic info for making of proteins is encoded in a series of 3 mRNA nucleotides called codons. Each one of them codes for a specific amino acid. But some of them dont code for an AA at all, instead they can signal for the translation to start or stop, like that other thing. Like in transcription, yeah. These are conveniently called stop and start codons. The (nitrogen) bases for the 3 nucleotides in the start codon is adenine, uracil, and thymine in that order (AUG). The ones for stop codons is UAA, UAG, and UGA. Translation Thats what the process of forming polypeptides (chain of amino acids, what protein is made of.Im awfully sleepy and Im getting lost here, sorry) from information from DNA encoded into RNA is called. It begins when mRNA leaves nucleus to get to Ribosome, where Protein Production Inc is located. tRNA and Anitcodons Amino acids happily floating around the cytosol are captured and stuck to tRNA, and are transported to ribosomes.
So THATS what they do! The other end opposite of where the amino acid attaches bears another triple nucleotide sequence much like codons, except these are called anticodons. With the amino acid attached, theyre meant to bond with the codons in that complementary base way we saw with the DNA/RNA transcription thing we saw in the first chapter. The pairing of these two codons along the mRNA ensure that the amino acid is added in the order transcribed by the mRNA chain. Ribosomes Ribosomes are usually doing their happy floating around the cytosol, or theyre glued to the endoplasmic reticulum. Poor things. The ones doing the floating is where the protein made is used inside of cell. Ribosomes have 3 binding sites that are the key to translation.
One site holds mRNA so that its codons is accessible to the rRNA molecules. The two other sites hold tRNA whose anticodons attach with the codons on the mRNA. Protein Assembly Okay, Im in a bloody hurry to finish this cause we already moved on to the next chapter, so Im gonna sum it up with the short, wise words of magical biology textbook: The process of assembling polypeptides from information encoded in mRNA is called translation. During translation, tRNA anticodons pair with corresponding mRNA codons, and amino acids are joined together to form a polypeptide. As a polypeptide folds and associates with other polypeptides, it assumes the functional structure of a completed protein. Review—– No time. THATS TOO BAD! D: Not that anyone actually reads through the whole thing (I like to think I do), but I rewrite the last parts and the review if anyone likes. Just leave a comment or e-mail or something and Ill get my lazy bum to it.