• Honors Biology DNA & Protein Synthesis Test Review list: (Ch. 10)

    1) Who discovered DNA structure?
    James Watson and Frances Crick

    2) What is the significance of the X-ray diffraction image
    of DNA taken by Rosalind Franklin?
    It showed DNA to be a Helical molecule (as well as other aspects of its structure).

    3) What is the basic structure and shape of DNA?
    The sides of the DNA molecule are made up of alternating deoxyribose sugars and phosphate groups.
    The middle (rungs of the ladder) of the DNA molecule is composed of Nitrogenous bases with hydrogen bonds between them.The shape of the DNA molecule is a double helix.

    4) What are the parts of a DNA nucleotide?

    phosphate group   Deoxyribose sugar   Nitrogenous base

    5) Compare and contrast the purines and the pyrimidines.
    Both purines and pyrimidines are nitrogenous bases
    purines - are made up of two carbon rings (adenine and quanine)
    pyrimidines - have only one carbon ring (thymine and cytosine and uracil in RNA)

    6) What is proper DNA base-pairing.
         A-T     G-C

    7) What happens during DNA replication, where is it located?
    DNA replication is responsible for the production of two identical DNA molecules in order that daughter cells will get the duplicate DNA.   It is a semi-conservative process because each molecule that results from replication has one original strand and one newly synthesized strand. This process happens in the nucleus.

    8) What enzymes are involved in DNA replication?
    Two of the major enzymes are:
    helicase - separates the two DNA strands
    DNA polymerase - bonds nucleotides to form the complementary strands of DNA proof-reads and corrects mistakes in the newly replicated strand (Ligase is another enzyme that bonds Okazaki fragments)

    9) What are Okazaki fragments?
    They are short replicated segments of DNA that occur along the lagging strand of DNA.

    10) What are the differences between DNA and RNA?
    DNA: Two strands, has thymine as one of its bases, has deoxyribose sugar
    RNA: One strand, has uracil instead of thymine, has ribose sugar

    11) What are the three types of RNA and how are they different from one another?
    mRNA = messenger RNA - single strand with no loops. contains codons that represent amino acids
    tRNA = transfer RNA - single strand that is looped. contains anticodons that match mRNA codons.  It carries amino acids to the ribosome for protein synthesis.
    rRNA = ribosomal RNA which, together with proteins, makes up the ribosome

    12) What are the major parts of tRNA?

    13) What are the stages of RNA transcription, What happens at each stage?
    Where is it located? What are the enzymes involved?
    Transcription takes place in the nucleus.
    Initiation - RNA polymerase moves to the promoter region of the gene. DNA strands separate,
    Elongation - RNA polymerase moves along the template of the coding strand as RNA nucleotides bond.
    Termination - RNA polymerase reaches the terminator region of the gene and transcription stops. RNA polymerase leaves, DNA strands rebond, and mRNA is then processed.

    14) How are ribosomes synthesized and of what are they composed?
    They are produced by the nucleolus and are composed of rRNA and protein.

    15) How many amino acids are coded for by a structural gene of 900 nucleotides?
    300 (three nucleotides per amino acid)

    16) What is meant by the term coding strand in reference to DNA?
    It is the strand that is complimentary to DNA template strand.
    The template strand is the guide used to produce a RNA molecule during transcription.


    17) Compare and contrast codon and anticodon.
    The codon and anticodons both consist of three RNA nucleotides in sequence.
    Codons are found in mRNA and anticodons are found in tRNA.

    18) Distinguish between introns & exons.
    introns are edited from mRNA and exons are spliced together.  Exons contain the genetic code, while introns do not and are therefore not needed.

    19) What is meant by the term RNA transcript?
    It is the RNA molecule produced through transcription. An RNA molecule that has not yet been processed is called a primary transcript.

    20) What is the significance of the mG-cap & the poly-A-tail of mRNA?
    they are thought to protect the mRNA from enzymes in the cytosol

    21) List & describe the stages of translation. Where does it occur in the cell?
    Translation occurs in the cytoplasm at a ribosome.
    Initiation - ribosome assembles at messenger RNA. The first tRNA brings methionine to the start codon.
    Elongation - Another tRNA brings the next amino acid to the ribosome. The two amino acids bond. The ribosome moves along the mRNA and the process repeats as more tRNAs bring amino acids to the growing protein.
    Termination - the ribosome moves to a stop codon on the mRNA. A protein called a release factor causes the end of protein synthesis. The ribosome leaves mRNA and the protein is then processed.

    22) What is meant by the term charged tRNA?
    It is a tRNA with an amino acids attached.

    23) What is the role of GTP (Guanosine Triphosphate)?
    It is the molecule that provides energy for charging tRNAs and assembling the ribosome.

    24) What is the significance of the start and stop codons?
    Start codons signals the beginning of protein synthesis. It is AUG on mRNA and represents the amino acids methionine.  Stop codons signal the end of protein production.

    25) Whats significance of the P (peptide) & the A (Amino acyl) site of the ribosome?
    The first tRNA brings an amino acid to the P site of the ribosome, while the second tRNA brings the next amino acids to the A site. When the amino acids bond, the tRNA at the A site moves to the P site. Another tRNA then moves to the A site to bring the next amino acid during protein synthesis.
    26) What is meant by the term polyribosome or polysome?
    Many ribosomes together at the same mRNA in the cytosol.

    27) What happens in the nucleolus?
    ribosome subunits are produced

    28) Whats significance of the signal sequence of a newly synthesized polypeptide?
    It directs where the protein goes in the cell after it is synthesized.

    29) What are: RER, Golgi & the cytomembrane systems roles in processing proteins?
    Proteins produced at the RER are exported from the cell (proteins produced at free ribosome stay in the cell). Proteins are modified in the RER. Vesicles with the protein move to the Golgi and are further modified. Vesicles with the protein move from the Golgi to the cell membrane and are exported form the cell by exocytosis.

    30) Be able to list the amino acids for a certain mRNA strand.
    You should be able to use the codon wheel.

    31) What is meant by recombinant DNA?
    DNA that is recombined in genetic engineering. (such as insertion of genes into bacterial genomes)

    32) What is DNA fingerprinting?
    Producing a pattern of dark bands from fragments of DNA in a sample.  It can be used in criminology and  forensics, as well as establishing paternity and evolutionary studies etc.

    33) What is a restriction enzyme? What is gel electrophoresis?
    restriction enzyme - cuts DNA at specific regions into fragments
    gel electrophoresis is used to separate the DNA fragments during DNA fingerprinting

    34) How is one protein different from another?
    kinds, amounts and arrangement of amino acids
    What causes the difference in proteins?
    different arrangement of amino acids

    35) What happens if a DNA molecule is

    transcribed incorrectly?
    a different protein may result (which may no function properly) If the mistake produces a codon that codes for the same amino acid, the protein
    produced may not be different.

    36) Be able to label a DNA diagram.

    37) Be able to use the codon wheel,

    or codon table.

    38) Be able to label a nucleotide.

    39) What is meant by the semi-conservative nature of DNA replication?
    Each new DNA molecule after replication has one original strand and one new strand.