BIO 111 TAMU Fletcher Exam 3 Already Graded A

BIO 111 TAMU Fletcher Exam 3 Already Graded A Friedrich Miescher discovered DNA in 1869 But did not know (Isolated phosphate) rich acidic compounds Frederick Griffith Discovered transformation during an experiment that involved injecting mice with smooth S cells, rough R cells, heat-killed S cells, and heat-killed S cells with living R cells. Avery, MacLeod, McCarty Identified the heritable substance as DNA Used test tubes- vitro Hershey and Chase performed experiments showing that DNA is the genetic material of a phage known as T2 chargaff A=T and C=G Wilkins and Franklin used X-ray diffraction to determine that the shape of DNA was a helix Waston and Crick Developed the current model for the DNA double helix; determine the structure of DNA DNA structure polymer of nucleotides, Nitrogenous base, Sugar, Phosphate group Nitrogenous bases in DNA adenine=2, guanine=3, cytosine=3, thymine=2 purine Adenine and Guanine (2 rings) Pyrimidine cytosine and thymine (single ring) DNA double helix Bound covalently, linked by phosphodiester bonds 3' 3rd carbon that has a hydroxyl group 5' 5th carbon that has a phosphate group Centromere joining point for replicated chromatids Telomere Nucleotide sequence at the end of the chromatids both ends chromatid 3 billion base pairs packed together DNA packaging DNA strand to Nucleosome to 30 then looped domains (10,30,300,700) 10nm fiber Nucleosomes connected by stretches of DNA Bead formation 30 nm fiber interactions between nucleosomes cause the thin fiber to coil or fold into this thicker fiber 300 nm fiber The 30-nm fiber forms looped domains that attach to proteins 700 nm fiber looped domains coil further only seen in metaphase the relationship between structure and function of DNA Manifested in the double helix (important for replication and repair) DNA replication DNA unzips into two parts and splits with the cell. In it's new home each side of the DNA strand attack to matching nucleotides to create 2 exact copies. conservative replication Original parent strand remains intact, 2 completely new helix are synthesized semi-conservative replication parent strand comes apart and each new helix has part of the parent dispersive replication both original strands are broken up into small pieces incorporated into newly synthesized strands Mesleson and Stahl Showed that semi-conservative was how DNA replicated Prokaryote DNA replication starts from a single point and proceeds in two directions until the entire chromosome is copied Replication fork A Y-shaped region on a replicating DNA molecule where new strands are growing. Toposiomerase corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands single strand binding proteins bind to a single-stranded DNA and prevents it from reforming Primase synthesizes RNA primer DNA polymerase III synthesizes new DNA only in the 5' to 3' direction with the help of RNA primer DNA polymerase I Replaces RNA with DNA DNA ligas Seals the gaps between Okazaki Fragments What is different from eukaryotes and prokaryotes in replication Eukaryotes can have thousands of repliation origins per chromosome In what end is the nucleotides attached during DNA replication? and what functional group is found here? 3' Hydroxyl Group leading strand the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction lagging strand A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork. What are challenges for DNA replication Torsion, Antiparallel Elongation, Priming DNA synthesis Torsion Being to twisted Antiparallel Elongation each strand of DNA faces in an opposite direction DNA replication machine Stationary Complex What is the error rate of DNA replication? 1/10,000 nucleotide excision repair The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide. End of replication chromosomal They get shorter because RNA primer can not be replaced with DNA (Eukaryotic) Dont have the problem because they are circular DNA (prokaryotes) Telomeres DNA at the tips of chromosomes to help prevent Erosion of DNA silent mutation The base pair changes but does not change the amino acid missense mutation The base pair changes and so does the sequence of amino acids nonsense mutation The base pair changes and causes a stop codon Sickle Cell mutation Point or missense mutation frameshift mutation mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide chromosomal mutation A change in the chromosome structure, resulting in new gene combinations. What is the process by which DNA directs protein synthesis Gene Expression Two stages of gene expression 1. Transcription 2. Translation Beadle and Tatum The "one gene-one enzyme" hypothesis that the function of a gene was to make a specific enzyme what do we now know that genes encode for? Polypeptide chains What is the central dogma? DNA-transcription-RNA-translation-protein what is the first step of gene expression transcription, which has a main goal of converting a sequence of DNA into a single stranded mRNA. what is the second step of gene expression translation, Reading the mRNA and making Amino Acids How many bases correspond to an amino acid there are 21 amino acids and 4 nucleotides How many possible codons 64 How many different amino acids are there? 21 How many stop codons? 3 (UAA, UAG, UGA) How many start codons? 1 (AUG) (met) The genetic code is... a nearly universal sequence of nucleotides in DNA that determines the specific amino acid sequence in the synthesis of proteins. What synthesis of RNA under the direction of DNA to produce mRNA to make a template for translation Transcription What actually synthesis of a polypeptide and occurs on ribsomoes Translation When does transcription and translation happen in prokaryotes Together When does Transcription and translation occur in Eukaryotes RAN transcripts and then is modified to them be translated what does a start codon encode for Methionine Transcription step 1 Initiation: RNA Polymerase binds to a promoter Transcription step 2 Elongation: RNA Polymerase adds complementary basses, substituting U's for T's (A-G U-C) Transcription step 3 Termination: RNA polymerase detaches and releases transcript upon reaching terminator sequence on DNA template what is the transcribed code to terminate in transcription for Eukaryotes AAUAAA Polyadenylation RNA polymerase I transcribes rRNA RNA polymerase II transcribes mRNA RNA polymerase III transcribes tRNA Post transcription processing Modifications of primary mRNA creates a complete, mature mRNA How is mRNA altered before it leaves the nucleus? gets a 5' cap and a 3' Tail RNA splicing Process by which the introns are removed from RNA transcripts and the remaining exons are joined together. The presence of introns allow.... Alternative RNA splicing Translation Process by which mRNA is decoded and a protein is produced What is aminoacyl tRNA synthetase- it joins each amino acid to the correct tRNA What facilitates the specific coupling of tRNA anticodons with mRNA codons during protein synthesis? Ribosomes translation step 1 Initiation: tRNA, ribosome, and mRNA, come together CODON on mRNA pairs with Anti-Codon on tRNA Translation step 2 elongation Amino acids are added 1 by 1 to preceding amino acid translation step 3 termination when the ribosome reaches a stop codon what are the 2 popilations of ribsomes in a cell Free and Bound free ribosomes suspended in the cytosol substitution mutation A single nucleotide is replaced by a different nucleotide insertion/deletion mutation addition or deletion of base pairs in DNA mutagens A chemical or physical agent that interacts with DNA and causes a mutation. examples- UV X-rays Somatic cells body cells operons genes that coordinate the regulation of gene expression 3 types of operons repressors, activators, inducer- activate or suppresses where are repressors and activators produced in the cell where are inducers produced in the cell or in the cells environment Tryptophan Repressible, 5 gened to transcribe as a single mRNA, if plentiful- operon is turned off Lac Operon cap when glucose levels fall e Coil uses other sugars for fuel. go more in depth regulation differences between prokaryotes and eukaryotes P- lacks nuclues, can be transcript and translate at the same time e- Nucleus, gets transcript then add cap and tail then out of nucleus to cytoplasm and is translate