Bio 21 exam 3

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cheerios258
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Bio 21 exam 3
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2015-04-30 23:59:19
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DNA
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Gene expression, DNA replication...
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  1. What is the one-gene-one polypeptide hypothesis?
    It started out as one-gene-one enzyme hypothesis but has evolved because genes code for polypeptides.
  2. The synthesis of RNA under the direction of DNA is the process of ___.
    Transcription
  3. What carries a genetic message from the DNA to the protein-synthesizing machinery of the cell?
    mRNA
  4. ____ is the actual synthesis of a polypeptide which occurs under the direction of mRNA.
    Translation
  5. Where is the site of translation occurring?
    Ribosomes

    • -in prokaryotes: in same area
    • -in eukaryotes: outside of nucleus
  6. What are the 2 reasons for proteins not being directly translated in the DNA.
    • 1. It provides protection for the DNA and the genetic information keeping the original undamaged.
    • 2. It allows for more copies of the protein to be made simultaneously
  7. The DNA of a ___ cell is not segregated from ribosomes and the other protein-synthesizing equipment.
    The DNA of a prokaryotic cell is not segregated from ribosomes and the other protein-synthesizing equipment.
  8. Gene program protein synthesis via genetic messages in the form of ___.
    Gene program protein synthesis via genetic messages in the form of mRNA.
  9. There are only __ nucleotide bases to specify __ amino acids.
    There are only _4_ nucleotide bases to specify _20_ amino acids.
  10. How many nucleotide bases form to code an amino acid?
    3 nucleotide bases called a triplet aka triplet code.
  11. TRUE or FALSE
    For each gene during transcription only one of the two DNA strands is transcribed.
    True
  12. The strand that is being transcribed during transcription is called the __ strand.
    The strand that is being transcribed during transcription is called the template strand.
  13. Is an mRNA strand identical to the DNA strand?
    The mRNA is not identical to the DNA strand, it is a complimentary to the DNA.
  14. What are the pairs for DNA?
    • A-T
    • T-A
    • C-G
    • G-C
  15. What are the nucleotide base pairs for RNA?
    • C-G
    • A-U
    • G-C
    • T-A
  16. Uracil (U) takes the place of what nucleotide in RNA?
    Thymine (T)
  17. The mRNA base triplets are called ___.
    The mRNA base triplets are called codons.
  18. TRUE or FALSE
    When the DNA strand template is transcribed to make mRNA the DNA strand is read from 5' -> 3' so that the RNA strand is written in 3'->5'.
    False.

    The DNA strand is read from 3' to 5'. The mRNA strand, because it is complimentary, is written in 5' to 3'.
  19. There are 64 triplet codons for amino acids, how many are designated as stop signals and how many are start signals?
    3 codon signal for stop. Only 1 codon (AUG) is a start codon.
  20. TRUE or FALSE
    There is redundancy in the genetic code, but no ambiguity.
    True
  21. What is the function of RNA polymerase?
    It pries the two strands of DNA apart and hooks together the RNA nucleotides
  22. Do RNA polymerase need a primer to start a chain?
    no
  23. What is the role of a promotor in RNA synthesis?
    It is where the RNA polymerase attaches and initiates transcription
  24. What does a transcription unit include?
    The stretch of DNA that is transcribed into an RNA molecule.
  25. There are 3 steps in transcription, what are they?
    • 1. Initiation
    • 2. Elongation
    • 3. Termination
  26. What happens during the Initiation phase of transcription?
    RNA polymerase binds to the promotor, the DNA strands unwind and the polymerase initiates RNA synthesis at the start point on the template strand.
  27. What happens during the elongation phase in transcription?
    The polymerase moves downstream, unwinding the DNA and elongation the RNA transcript 5' to 3'. The DNA strands re-form a double helix.
  28. What happens during the termination phase of transcription?
    Eventually the RNA transcript is released and the polymerase detaches from the DNA.
  29. What is the TATA box?
    Eukaryotic promotors include TATA box, it is the beginning portion of the promotor.
  30. In eukaryotoic cells the promotor includes ...
    The TATA box and the start point.
  31. What are the step for a eukaryotic cell initiation of transcription at the promotor?
    • -Several transcription factors, one recognizing the TATA box, must bind to the DNA before RNA polymerase II can.
    • - Additional transcription factors bind to DNA along with RNA polymerase II, forming the transcription initiation complex.
    • -The DNA unwinds and RNA synthesis begins at the start point on the template strand.
  32. TRUE or FALSE
    During elongation RNA polymerase moves along the DNA adding nucleotides to the 3' end of the growing RNA molecule.
    TRUE
  33. What is the difference in prokaryotes and eukaryotes in the termination phase of transcription?
    Prokaryotes: there is a terminator sequence signaling the polymerase to detach from DNA and release the transcript.

    Eukaryotes: pre-mRNA is cleaved from growing chain as polymerase continues on. further downstream the pre-mRNA is released. The termination ends when the polymerase eventually falls off.
  34. Where does transcription occur in prokaryotes and eukaryotes?
    prokaryotes:within in the cell-there's no nuclei

    eukaryote: within the nucleus
  35. What must happen to pre-mRNA before it can leave the nucleus to be translated?
    A 5' cap end must form in the 5' end of the pre-mRNA and a poly-A tail must form on the 3' end.
  36. In a eukaryotic cell what releases the pre-mRNA?
    The polyadenylation signal, AAUAAA.
  37. Why are the ends of the pre-mRNA altered?
    The 5' cap and the poly-A tail help:

    1. Facilitate export of mature mRNA out of nucleus.

    2. To help protect the mRNA from degradation by hydrolytic enzymes.

    3. Both structures help ribosomes attach to the 5' end of the mRNA.
  38. What purpose does the untranslated regions at the 5' and 3' ends of mRNA serve?
    These parts will not be translated, but they do help with ribosome binding.
  39. What is RNA splicing?
    The removal of large portion of the RNA molecule that is initially synthesized.
  40. The noncoding segments of nucleic acid that lie between coding regions are called ___.
    The noncoding segments of nucleic acid that lie between coding regions are called introns.
  41. What are exons?
    The portion that gets expressed into amino acids.
  42. TRUE or FALSE
    The exons are removed from the molecule and the introns join together forming an mRNA molecule with continuous coding sequence.
    • FALSE
    • The introns are removed from the molecule and the exons join together forming an mRNA molecule with continuous coding sequence.
  43. What is are snRNPs ("snurps")?
    Particles that recognize a short nucleotide sequence at the end of an intron as splice sites.
  44. What is a spliceosome?
    It is several different snRNPs join with additional proteins to form a spliceosome.

    It releases the intron and joins together the two exons that were on either side of the intron. 
  45. The spliceosome then comes apart, releasing splice mRNA, which now contains only ___.

    A. introns
    B. snRNPs
    C. exons
    C. exons
    (this multiple choice question has been scrambled)
  46. Alternative RNA splicing is...?
    A type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary  transcript, depending on which RNA segments are treated as eons and which as introns.
  47. Proteins often have a modular architecture consisting of discrete structural and functional regions called ____.
    Proteins often have a modular architecture consisting of discrete structural and functional regions called domains.
  48. Which statement is false?

    a. Different exons code for different domains of a protein.

    b. In a large number of genes, different exons encode separate domains of the protein product.

    c. One domain only codes for the entire protein product.
    c. 

    - Domains can encode separate components of a protein such as attachment or determine the what will be the active site of the protein.
  49. What is does tRNA stand for and what is the function of tRNA?
    tRNA is transfer RNA. 

    The function is to transfer amino acids from the cytoplasmic pool of amino acids to the ribosomes.
  50. TRUE or FALSE
    All 20 amino acids are just hanging out in the cytoplasm of the cell.
    True.

    Amino acids are taken from surrounding solutions or are synthesized from other compounds to keep the cytosol stocked.
  51. Why are amino acids brought to the ribosomes from the tRNA?
    The ribosome adds them together to make polypeptide chains. 
  52. Which statement is false?

    a. Molecule of tRNA are all identical.

    b. tRNA bears a specific amino acid at one end.

    c. Each tRNA translates a particular mRNA codon into a particular amino acid.
    a. Molecule of tRNA are all identical.

    - Molecules of tRNA are not all identical because each one carries a specific amino acid.
  53. Anticodon is...?
    A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
  54. TRUE or FALSE
    Each tRNA contains an anticodon on one end and an attachment site on the other end.
    TRUE
  55. What is the job of an aminoacyl-tRNA synthetase?
    An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA.
  56. What are the 3 binding sites for mRNA to bind to ribosomes?
    The P site, A site, and the E site.
  57. What are the roles of the 3 binding sites of the ribosome?
    P site: holds the tRNA carrying the growing polypeptide chain

    A site: hold the tRNA carrying the next amino acid to be added to the chain.

    E site: where discharged tRNA leave the ribosomes.
  58. The two subunits that make up the ribosomes are the ___ and the ____.
    The two subunits that make up the ribosomes are the large subunit and the small subunit.
  59. Describe the initiation stage of translation in building a polypeptide chain.
    The small subunit of ribosome binds to mRNA and tRNA and finds the start codon AUG (mRNA) and UAC (tRNA) in the sequence.

    - The large subunit then attaches to complex the translation initiation complex.

    - initiation factors help bring all these factors together using GTP as energy to do so.
  60. Describe the elongation phase of translation.
    • - Codon recognition. tRNA containing the complementary base pair of the mRNA binds to the A site. (GTP hydrolysis)
    • -Peptide bond formation. Large subunit catalyzes new bond between the new amino acid in the A site to the growing end of chain at the P site which attaches the tRNA to A site.
    • -Translocation. The tRNA is moved to P site where it is emptied and moved to the E site to be released
  61. When release factor binds directly to the stop codon in the A site does this terminate translation?
    Yes. Release factor causes the addition of a water molecule which hydrolyzes the polypeptide and leads it to the P site and releases through the exit tunnel.
  62. Polyribosomes can attach to a string of mRNA to make many copies of a polypeptide quickly. How?
    One ribosome moves past the start codon on the mRNA strand and another ribosome can attach to the same mRNA strand after it has moved past the start and so on.
  63. What is aneuploidy?
    a chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number
  64. What is trisomic?
    Referring to a cell that has three copies of a particular chromosome instead of the normal two.
  65. what is monosomic?
    It refers to a cell that has only one copy of a particular chromosome instead of the normal two.
  66. polyploidy
    A chromosomal alteration in which the organism possesses more than two complete chromosome sets.
  67. What is an allele?
    Alleles are alternative versions of a gene that produce distinguishable phenotypic effects
  68. Homozygous
    An organism having a pair of identical alleles for a character
  69. Heterozygous
    An organism that has two different alleles for a gene
  70. Phenotype
    The physical and physiological traits of an organism which are determined by its genetic makeup
  71. Genotype
  72. what is the difference between a monohybrid and dihybrid?
    Monohybrid:an organism that is heterozygous with respect to a single gene of interest.

    Dihybrid: an organism that is heterozygous with respect to two genes of interest.
  73. What is the law of independent assortment?

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