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Biology 12: Unit 3
Unit 3 of Bio
| Question | Answer |
|---|---|
| What are the three parts of DNA? | nitrogenous base, pentose sugar (deoxyribose) and a phosphate group |
| Distinguish Pyrimidines from Purines | Pyrimidine = smaller, Purine=larger |
| name the Pyrimidine | cytosine, thymine |
| name the purines | adenine and guanine |
| What is on the outside of a DNA molecule? | the sugar-phosphate backbone |
| How many strands of DNA? | two |
| Where is genetic information stored? What is it made out of? | Chromatin; DNA combined with small protein molecules called histones. |
| What is the DNA's form when cells are no dividing? | its unwound form and is actively engaged in controlling cellular acivites by governing the synthesis of proteins |
| What happens to chromatin after replication? | chromatin coils about histones becoming more densely packed and visible |
| What is DNA? | a double stranded helical polymer of nucleotides |
| are nitrogenous bases hydrophobic or hydrophilic? | hydrophobic |
| When does helix make one full turn? | ever 3.4nm along its length, 10 layers of base pairs in each full turn of the helix |
| Why do purines pair with pyrimidines? | because of its uniform diameter |
| How many H-bonds between adenine and thymine? | 2 |
| how many h-bonds between Guanine and cytosine? | 3 |
| What is complimentary base pairing? | A is complimentary to T, G is complementary to C |
| What is the model for replication? | the Semi-conservative model |
| explain the semi conservative model | One parent strand, one new strand |
| When does replication begin? | during interphase |
| What requires cell division? | the growth of multicellular organisms and the repair and maintenance of their tissues |
| How many DNA molecules in each cell? | 46 |
| what is a replication fork? | Y shaped regions where paretal strands are being unwrapped |
| What is DNA Helicase? what does it do? | an enzyme that unwists the double helix @ the replication fork, separating the two parental strands & making them available as template strands. |
| What binds to parental strands as they separate? Was is its purpose? | single stranded binding proteins; keeps the unpaired dna strands from re-pairing. |
| What is the initial chain that is produced in DNA synthesis? How is it synthesized? | a short stretch of RNA chain; syntehsized by RNA Primase. |
| Where does the new DNA strand begin? | the 3' of the RNA primer. |
| What does DNA polymerase do? | catalyzes the synthesis of new DNA by adding nucleotides to a pre-existing chain. |
| What is elongation? | the addition of nucleotides |
| What does DNA Pol II do? | adds DNA nucleotide to the RNA primer & continues adding DNA nucleoides complemenary to the parental DNA template strand & to the growing end of the new DNA strand. |
| Which was does DNA Pol elongate? | 5' --> 3' |
| What does DNA Pol III do on the leading strand? | continuously adds nucleotides to the new complementary strand as the fork progresses --> needs only one primer |
| What does DNA Pol II do on the lagging strand? | working away from the replication fork, it synthesizes discontinuously as a series of okazagi fragments. |
| Difference between leading and lagging strand? | leading: 5' --> 3', lagging: 3' --> 5' |
| What does DNA ligase do? | joins the okazagi fragmens into a continuous DNA strand. |
| What is another job of the DNA polymerase | profreading each nucleotide against its template. |
| What is Mismatch repair? | enzymes remove and replace incorrectly paired nucleoides hat have resulted from replication errors. |
| What is permanent incorrect DNA pair called? | mutations-->occur after succesive replications |
| Why does each cell continuously monitor and repair its genetic material? | Because repair of damaged DNA is imporatnt to the survival of he cell. |
| What are the steps to proofreading and repairing DNA? | 1) enzymes detect damage DNA, 2) Nuclease cuts DNA at two points and section is removed, 3) polymerase fills in missing nucleotides, 4)ligase seals the free end of the new DNA & old DNA |
| What are telomeres used for? What are they? Why do they do this? | for linear DNA (ex. Eukaryotic). Don't contain genes, but multiple repitions of one short nucleotide sequence (ex. TTAGGG repeated 1,000 times). Acts as a buffer zone to prevent staggered ends caused by not being able to complet the 5' end. |
| How do telemores protect? What happens to them after every round of replication? | they postpone the erosion of genes located near ends of DNA molecules; they get shorter after every replication |
| Two functions of DNA? | replication and protein synthesis |
| Where does proein synthesis occur? | ribosomes attached to the E.R. or ribosomes attached floating in the cytoplasm. |
| Where is protein made if it will be used for cell structures of metabolic activites? | ribosomes in he cytoplasm |
| Where is protein made if they are to be exported? | in the E.R. to follow the secratory pathway and be exported via exocytosis. |
| What proteins are made in the RER? | hydrolic enzymes-->eventually packaged into lysosomes by Golgi body where they are used for intracellular digestion |
| What is the flow of information from DNA to protein? | DNA, mRNA, protein |
| What process is used to transfer information froom DNA to mRNA | transcription |
| What process is used to transfer information froom mRNA to protein? | translation |
| What is gene expression? | the process by which DNA directs the synthesis of proteins. |
| What do genes provide? | the instructions for making specific proteins |
| What is Transcription? | synthesis of RNA using info in DNA |
| what does mRNA do? | it carries a genetic message from the DNA to the protein sythesizing machinery of the cell |
| What is Translation? | synthesis of polypeptide using the information in the mRNA -->cell translates nucleotide sequence of mRNA monlecule into amino acid sequence |
| How many amino acids? | 20 |
| What are the smallest uni of uniform length that can code for all amino acids? | triplets of nucleotides |
| What is a template strand? | the strand that is transcribed (only one side is transcribed) |
| What are codons? | mRNA triplets written in 5' -> 3' They are complementary to the template strand |
| What is the start codon? | AUG |
| In protein synthesis, what does RNA polymerase do? | prise the two strnds of DNA apart and joins together RNA nucleoides complementary to the DNA template strand -->elongating the RNA polynucleotide (primer not needed) |
| What is a promoter? | the DNA sewuence where RNA polymerase attaches and initiates transcription |
| What is the transcription unit? | the stretch of DNA that is transcribed into RNA |
| In synthesis of RNA transcript what are the 3 stages? | initiation, elongation, termination |
| What do transription factors do? | meditatie the binding of RNA polymerase and the initiation of transcription --> only after transcription factors are attached to the promoter does RNA Pol II bind to it (the DNA) |
| What is transcription initiantion complex? | complex of transcription factors and RNA polymerase II bound to the promoter |
| What do eukaryotic cells do to RNA after transcription? | enzymes in it modify pre-RNA in specific ways before the genetic messages are dispatched to the cytoplasm |
| How do enzymes in eukaryotic cells modify RNA after transcription? | 1)Add a 5' cap, 2)3' end is modified and a poly-A-tail is formed (250 adenine) |
| What does the 5' cap and poly-A-tail do? | 1)facilitates export of mature RNA from nucleus, 2) Protects mRNA from degration by hydrolic enzymes, 3)help ribosomes attach to 5' end of mRNA |
| What is RNA splicing? | when large portions of RNA molecule is removed |
| what are introns? | noncoding segmens that lie between coding regions |
| what are exons? | regions that are eventually express, usually by being translated into amino acid sequences |
| How is splicing carried out? | by and RNA splicing signal @ the end of an intron -->small nuclear ribonucleoproteins (snRNPs) recognize splice sites |
| what is a spliceosome? | several snRnPs that join with addition proteins to form an even larger assembly |
| what does the cell do in translation? | it "reads" a genetic msg & builds a polypeptide accordingly |
| What is the msg that the cell reads? | a series of codons along and mRNA molecule. |
| What translates the msg? | tRNA translates he message into the sequence of amino acids. |
| what are on the opposite ends of the tRNA molecule? | an anticodon and a specific amino acid |
| how is tRNA a translator? | it translates a nucleic acid word (mRNA codon) and interprets it into the protein word (amino acid). |
| what are the steps to a tRNA bringing a amino acid to the ribosome? | 1)picks up designated amino acid in cytolsol, 2)deposits cargo on polypeptide chain @ ribosome 3)repeat |
| what is aminoacyl-tRNA synthesis? | the matching of tRNA and amino acids |
| what is the job of the ribosomes in protein synthesis? | to facilitate the specific coupling of tRNNA anticodons w/ mRNA codons |
| What is the initiation stage of protein synthesis in regards to the ribosome? | brings together mRNA, tRNA with first amino acid and two subunits of ribosome |
| What is the initator amino acid? | metione |
| what follows the union of mRNA, initiator tRNA and small subunit? | followed by the attachement of the large subunit |
| What brings all the factors (mRNA, initiator tRNA, small & large ribosomaal subunit) together? | initation factors |
| How is elongation terminated? | stop codon in mRNA reaches the A-site of the ribosome |
| What are the stop codons? | UAG, UAA & UGA (remember these are codons NOT anticodons...this is what is found on the mRNA strand) |
| What does a release factor do? | it binds directly to stop codon in the A-site, causing addition of water molecule instead of an amino acid. This hydrolyzes the bond btwn the completed polypeptide & tRNA in P Site |
| Why does a polypeide chain begin to coil during its synthesis? | it is a consequence of its amino acid sequence forming a protein with a specific 3D shape |
| What are mutations? What are they responsible for? | changes to the genetic information of a cell; responsible for huge diversiy of genes found amoung organisms b/c mutations are ultimate source of new genes |
| What is point mutation? | change in a single nucleotide -->it is a small scale mutation -->can be transmitted to offspring |
| What are the two types of point mutation? | 1) substitution , 2)Instertions/Deletions |
| What are substitutions? | replacement of one nucleotide & partner with another pair of nucleotides |
| What is a silent mutation? | a type of substitution where the substituded nucleotide has no effect on protein because the codon still calls for the right amino acid |
| What is a missense mutation? | When the amino acid is changed due substitution -> may have little effect has amino acids can have the simillar properies |
| What is a nonsense mutation? | when the substituted nucleotide changes the codon to a stop codon --> causes premature termination -->almost always leads to non-functional proteins |
| What are Insertions or Deletions? | additions or loses of nucleotid pairs in a gene. |
| What is frameshift mutation? | when he reading frame of the genetic msg (the triplet grouping of nucleotides on the mRNA) is altered -->occurs when # of nuucleotide inserted or deleted is not a multiple of three |
| What happens in an insertion or deletion mutation? | all nucleotides downstream of deletion or insertion are improperly grouped, resulting in extensive missense usually ending in nonsense and premature termination |
| What does a mutagen do? | interact with DNA in ways that cause mutations --> are physical/chemical agents |
| summarize Protein Synthesis | 1)Transcription, 2)RNA processing, 3)mRNA leaves nucleus & attaches to ribosome, 4)Amino acid activation, 5)Translation, 6)Termination |
| Why is the genetic code termed degenerative? | the significance of changes to the codon lessen as the triplet is read L to R |
| What does recombinant DNA technology allow scientists to do? | allows them to insert a segment of DNA from one organism into a chromosome of another |
| What is a plasmid? | the circular piece of DNA from a bacterium |
| What are the two most common mutagens? | chemical and radiation |
Created by:
db5k
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