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FSU BSC 2010 - Biology Final Exam Comprehensive Study Guide

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Biology Final Exam Comprehensive Study GuideChapter 17- Transcription and RNA processing•Background info:•DNA Replication- double helix splits the two helices and separate from each other to become templates for each other by pairing bases with their complementary pairs through attraction.•DNA transcription- double helix splits but instead of having deoxyribonucleic acid nucleotides pair up the mRNA nucleotides will pair up is the step where you go from DNA to mRNA and the mRNA leaves the nucleus of the cells and goes to the ribosomes•DNA Translation - is the process of making a linear chain of amino acids (polypeptide chain) in which the amino acids are joined by peptide bonds. The sequence of amino acids in the polypeptide chain is determined by the sequence of nucleotides in the mRNA. Every three nucleotides in the mRNA is a codon that codes for one amino acid.•RNA STRUCTURE:•Hairpin: is a pattern of intermolecular base-pairing that occurs when two regions of the same strain usually complementary nucleotide sequence when read in opposite directions, base pair to form a double helix that ends in a unpaired loop.•The formation of this structure depends on its stability.•Bulges or number of mismatched base-pairs, affects this. Only a small amount are okay.•Pseudoknot: contains at least two stem-looped structures in which half of one in intercalated between the two halves of another•Internal loops: interruptions in the helical structures of RNA.•Messenger RNA is transcribed from the template strand of a gene, it is the cell’s protein synthesizing machinery. •Transcription: the synthesis of RNA using a DNA template•RNA polymerase, an enzyme pries the two strands of DNA apart and joins the RNA nucleotides as they base-pair along the DNA template.•just like DNA polymerase, RNA polymerase can only assemble a polynucleotide in its 5’ -> 3’ direction. •RNA however, is able to start a chain from scratch without a primer. •Specific sequences of nucleotides along the DNA mark where transcription of a gene begins and ends.•Promoters: are the DNA sequences where RNA polymerase attaches and initiate transcription, and also determines which of the two strands of the DNA helix is used as a template.•Terminator: signals the end of transcription in bacteria.•The direction of transcription is considered downstream, and the other direction is considered upstream. •The terms describe the positions of the nucleotide sequences within the DNA or RNA. •Promoter sequence is thus, upstream from the terminator.•RNA Polymerase II is used for mRNA synthesis•The other RNA polymerases (I and III) are used to transcribe molecules not used for synthesis.•Synthesis of an RNA Transcript is in order as follows:1•Initiation: after RNA polymerase binds to the promoter, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand.•in bacteria, RNA polymerase binds directly to the promoter, but in eukaryotes, transcription factors (a collection of proteins) mediate this binding of RNA polymerase and the initiation of transcription.•Transcription Initiation Complex: is the whole complex of transcription factors and a crucial promoter DNA sequence know as a TATA box.•Elongation: Polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5’ -> 3’. IN the wake of transcription, the DNA strands reform a double helix.•The RNA polymerase adds nucleotides to the 3’ end of the growing RNA molecule.•In the wake, the RNA peels away from the DNA template allowing the helix to reform.•Transcription is about 40 nucleotides per second•The gathering of multiple polymerases, simultaneously transcribing a single gene increases the amount of mRNA transcribed, helping the cell make the protein thats being encoded in large amounts.•Termination: Eventually the RNA transcript is released, and the polymerase detaches from the DNA.•In bacteria, transcription proceeds through a terminator sequence in the DNA, the transcribed terminator sequence is the termination signal causing polymerase to detach and release the transcript, immediately being used for mRNA.•In eukaryotes, RNA polymerase II transcribes a polyadenylation sequence, (AAUAAA) in the pre-MRNA. 10- 35 nucleotides down from that proteins cut the transcript free from the polymerase, releasing Pre- MRNA. But the polymerase continues transcribing DNA for awhile past the site where the pre- MRNA was released.•Post transcription-- mRNA leaves nucleus of the cell to ribosomes and proteins are then formed = Translation•RNA processing: when the enzymes in the eukaryote modifies pre-mRNA before the messages are dispatched to the cytoplasm.•During this process both ends of the primary transcript are altered. certain interior sections of the RNA are cut out and remaining parts are spliced together•Each end of a pre-mRNA molecule is modified in a different way.•The 5’ end is synthesized first, receiving a 5’ cap, a modified form of a guanine(G) nucleotide added to the end after transcription of the first 20-40 nucleotides.•The 3’ end is also altered before the mRNA exits the nucleus. It receives a Poly-A tail, an enzyme added 50-250 more adenine (A) nucleotides to the 3’ end after the (AAUAAA Polyadenylation signal)•UTR: untranslated regions, they lie at both ends of the sequence before the 5’ cap and poly A tail. They will not be translated into protein, but function with ribosome binding.•Both the 5’ cap and Poly A tail serve many functions:•facilitation of the export of the mature mRNA from the nucleus•protection of the mRNA from degradation by hydrolytic enzymes•helping ribosomes attach to the 5’ end of the mRNA once the mRNA reaches the cytoplasm.2•RNA splicing: the removal of large portions of the RNA molecule that is initially synthesized. •Since the average length of a human DNA molecule is 27,000 base pairs long, the RNA transcript is that long too. It takes only 1200 nucleotides in RNA to code for the average size protein of 400 AA. (triplets). These extra nucleotides are noncoding stretches that aren't translated.•The noncoding regions are interspersed between coding segments of the pre-mRNA. The sequence of DNA is thus split up into segments.•Introns: the noncoding segments of nucelic acid that are between coding regions.•Exons: the other regions on the DNA sequence, that are


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