LIFE102, Week 13 Notes
LIFE102, Week 13 Notes Life 102
Popular in Attributes of Living Systems
verified elite notetaker
Popular in Biology
This 6 page Class Notes was uploaded by Sydney Dingman on Monday April 18, 2016. The Class Notes belongs to Life 102 at Colorado State University taught by Erik N Arthun in Winter 2016. Since its upload, it has received 19 views. For similar materials see Attributes of Living Systems in Biology at Colorado State University.
Reviews for LIFE102, Week 13 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/18/16
Week 13 LIFE 102 Notes 4/11/16, Chapter 17 No Chapter 18 Genetic code o Genetic code is redundant (more than one codon may specify a particular amino acid) o Codons must be read in the correct reading frame in order for the right polypeptide to be produced o AUG is at the start of every protein o UAA, UAG or UGA are at the end of every protein o TAC-ATA-AAA-ATTAUG-UAU-UUU-UAAStart(Met)-Tyr-Phe- Stop(Last period) The Structure and Function of Transfer RNA o Molecules of tRNA are not identical Each carries a specific amino acid on one end Each has an anticodon on the other end The anticodon base-pairs with a complementary codon on mRNA o A tRNA molecule consists of a single RNA strand that is only about 80 nucleotides long o Flattened into one plane to reveal its base pairing, a tRNA molecule looks like a cloverleaf o Because of hydrogen bonds, tRNA twists and folds into a three- dimension molecule (roughly L-shaped) Translation o mRNA- Protein o Codon- amino acid o Molecule that translates: Transfer RNA (tRNA) o Anticodon: tRNA triplet that binds to codon o mRNA binds to ribosome o tRNA bring amino acids to ribosome o Ribosomal enzymes connect amino acids into a polypeptide Ribosomes o Facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis o 3 Binding sites for tRNA: P site: holds tRNA that carries the growing polypeptide A site: holds tRNA that carries the next amino acid to be added to the chain E site: exit site where discharged tRNA leave the ribosome Three Stages of Translation o The initiation stage of translation brings together mRNA, tRNA with the first amino acid, and the two ribosomal subunits o During the elongation stage, amino acids are added one by one to the proceeding amino acids o Termination occurs when a stop codon in the mRNA reaches the A site of the ribosome A site accepts a protein called a release factor The reaction catalyzed by the release factor releases the polypeptide, and the translation assembly then comes apart Polyribosome: A number of ribosomes can translate a single mRNA simultaneously forming a polyribosome o Polyribosomes enable a cell to make many copies of a polypeptide very quickly Bacterial gene expression o Bacteria does not have a nucleus o Transcription and translation can occur at the same place, at the same time Mutations: changes in DNA sequence o Point mutations: changes in just one base pair of a gene o A-T G-C: Base pair substitution o A-T ---: base pair deletion o --- G-C: base pair insertion o Possible consequences: 2 Less functional or non-functional protein No protein Sometimes they work better (Very rare) Types of Small-Scale Mutations o Point mutations within a gene can be divided into two general categories: Nucleotide-pair substitutions One or more nucleotide-pair insertions or deletions o A nucleotide-pair substitution replaces one nucleotide and its partner with another pair of nucleotides o Insertions and deletions are additions or losses of nucleotide pairs in a gene Substitutions o A nucleotide-pair substitution replaces one nucleotide and its partner with another pair of nucleotides o Silent mutations have no effect on the amino acid produced by a codon because of redundancy in the genetic code o Missense mutations still code for an amino acid, but not the correct amino acid o Nonsense mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein Insertions and Deletions o Insertions and deletions are additions or losses of nucleotide pairs in a gene o These mutations have a disastrous effect on the resulting protein more often than substitutions do o Insertion or deletion of nucleotides may alter the reading frame, producing a frame shift mutations WATCH VIDEO ANIMATION ON CANVAS OF THE PROCESS 4/13/16, Chapter 19, Viruses Structure of Viruses o Viruses are not cells 3 o Very small infectious particle consisting of nucleic acid enclosed in a protein coat, in some cases, a membranous envelope o Viruses are obligate intracellular parasites which means they can replicate only within a host cell General Characteristics of Viruses o Cannot reproduce or multiply unless they invade a specific (specific cell/species) host cell and instruct its genetic and metabolic machinery to make and release new viruses o Can infect every type of cell (bacteria, fungi, algae, etc.) o Obligate intracellular parasites Cannot exist independently from the host cell Non-living infectious particles (acellular) “Active or inactive” not “dead or alive” o contain only those parts needed to invade and control a host cell Viral capsids o A capsid is the protein shell that encloses the viral genome composed of capsomeres o Capsids are built from individual protein subunits called capsomeres Viral envelope o Some viruses have membranous envelopes (viral envelopes) that surround the capsid o Viral envelopes, which are derived from the host cell’s membrane, contain a combination of viral and host cell molecules Viral Structures Viruses that infect bacteria o Bacteriophages, also called phages, are viruses that infect bacteria o Phages have an elongated capsid head that encloses their DNA o A protein tail piece attaches the phage to host and injects the phage DNA inside Viral Genome Types o Double- or single-stranded DNA or Double- or single- RNA 4 o Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus o No virus will ever have both DNA or RNA Host Range & Tissue Tropism o Viruses are obligate intracellular parasites, which means they can replicate only within a host cell o Each virus has a host range (a limited number of species that it can infect; type of species) and tissue tropism (tissue specificity within a host; type of cell) General Features of Viral Replicative Cycles o Once a viral genome has entered a cell, the cell begins to manufacture viral proteins o The virus makes use of host enzymes, ribosomes, tRNAs, amino acids, ATP and other molecules o Viral nucleic acid molecules capsomeres spontaneously self- assemble into new viruses Replicative Cycle of a DNA virus o Viral DNA enters cell Replication, transcription, translation o Viral DNA and proteins made o Virus assembly, cell lysis Replicative Cycle of Phages o Phages have two reproductive mechanisms The Lytic cycle and Lysogenic cycle o Lytic Cycle The lytic cycle is a phage replicative cycle that leads to the death of the host cell The lytic cycle produces new phages and lyses (breaks open) the hosts cell wall, releasing the new virus o Lysogenic cycle The lysogenic cycle replicates the phage genome without destroying the host The viral DNA molecule is incorporated into the host cell’s chromosome 5 This integrated viral DNA is known as a prophage Every time the host divides, it copes the phage DNA and passes the copies to daughter cells An environmental signal can trigger the virus genome to exist the bacterial chromosome and switch to the lytic mode 6
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'