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Genetics (Mutations (Point mutations (chemical changes in just one…

- - - - Frameshift mutation
        
        The result will be extensive missense, ending sooner or later in nonsense—premature termination.
        
        All the nucleotides downstream of the deletion or insertion will be improperly grouped into codons.
- - - - messenger RNA is a copy of a gene. It acts as a photocopy of a gene by having a sequence complementary to one strand of the DNA and identical to the other strand. The mRNA acts as a busboy to carry the information stored in the DNA in the nucleus to the cytoplasm where the ribosomes can make it into protein.
    - - transfer RNA is a small RNA that has a very specific secondary and tertiary structure such that it can bind an amino acid at one end, and mRNA at the other end. It acts as an adaptor to carry the amino acid elements of a protein to the appropriate place as coded for by the mRNA.
    - - ribosomal RNA is one of the structural components of the ribosome. Its sequence is the compliment of regions in the mRNA so that the ribosome can match with and bind to an mRNA it will make a protein from.
    - - The most remarkable stage of RNA processing occurs during the removal of a large portion of the RNA molecule in a cut-and-paste job of RNA splicing.
      - RNA splicing removes introns and joins exons to create an mRNA molecule with a continuous coding sequence.
      - The signal for RNA splicing is a short nucleotide sequence at each end of an intron.
- - - - sugar-phosphate backbones on the outside of the double helix
      - the two sugar-phosphate backbones are antiparallel, with the subunits running in opposite directions.
      - sugar-phosphate chains of each strand are like the side ropes of a rope ladder
        
        Pairs of nitrogenous bases, one from each strand, form rungs.
        
        nitrogenous bases are paired in specific combinations: adenine with thymine and guanine with cytosine.
        
        The ladder forms a full turn of the helix every ten bases
  - - - in the prokaryotic bacterium E. coli, replication can occur at a rate of 1,000 nucleotides per second.
    - - in comparison, eukaryotic human DNA replicates at a rate of 50 nucleotides per second.
    - - Step 3
        
        After the primer is in place on a single, unwound polynucleotide strand, DNA polymerase wraps itself around that strand, and it attaches new nucleotides to the exposed nitrogenous bases.
        
        Beginning at the primer sequence, DNA polymerase (shown in blue) attaches to the original DNA strand and begins assembling a new, complementary strand.
      - Step 4
        
        As DNA polymerase makes its way down the unwound DNA strand, it relies upon the pool of free-floating nucleotides surrounding the existing strand to build the new strand.
        
        The nucleotides that make up the new strand are paired with partner nucleotides in the template strand; because of their molecular structures, A and T nucleotides always pair with one another, and C and G nucleotides always pair with one another.
        
        This phenomenon is known as complementary base pairing, and it results in the production of two complementary strands of DNA.
      - Step 2
        
        Meanwhile, as the helicase separates the strands, another enzyme called primase briefly attaches to each strand and assembles a foundation at which replication can begin.
        
        This foundation is a short stretch of nucleotides called a primer
      - Step 5
        
        A new DNA strand is synthesized. This strand contains nucleotides that are complementary to those in the template sequence.
      - Step 1
        
        First, a so-called initiator protein unwinds a short stretch of the DNA double helix.
        
        Begins at special site called origins of replication
        
        Then, a protein known as helicase attaches to and breaks apart the hydrogen bonds between the bases on the DNA strands, thereby pulling apart the two strands, forming a replication “bubble.”
        
        As the helicase moves along the DNA molecule, it continues breaking these hydrogen bonds and separating the two polynucleotide chains
    - - The ends of eukaryotic chromosomal DNA molecules have special nucleotide sequences called telomeres.
      - Telomeres do not contain genes. Instead, the DNA typically consists of multiple repetitions of one short nucleotide sequence.
      - Telomeric DNA acts as a kind of buffer zone that protects the organism’s genes. Telomeres become shorter during every round of replication.
- - - - There is a brief time during this process when the newly formed RNA is bound to the unwound DNA.
      - During this process, an adenine (A) in the DNA binds to an uracil (U) in the RNA.
      - the addition of nucleotides to the mRNA strand. RNA polymerase reads the unwound DNA strand and builds the mRNA molecule, using complementary base pairs.
    - - the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene
      - The mRNA strand is complete, and it detaches from DNA.
    - - occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter.
      - signals the DNA to unwind so the enzyme can ‘‘read’’ the bases in one of the DNA strands
      - the beginning of transcription
      - The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases.