RNA need to be removed to prevent degradation As each Okazaki fragment is

Rna need to be removed to prevent degradation as each

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RNA need to be removed to prevent degradation. As each Okazaki fragment is finished, the RNA primer is removed by RNase H and replaced with DNA by DNA polymerase. This process leaves nicks in the sugar-phosphate backbone of the DNA. DNA ligase seals the nicks to create a continuous strand of new DNA.
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DNA Polymerase Proofreads Newly Synthesized DNA: Proofreading activity known as 3’ -> 5’ exonuclease. 3’ → 5’ exonuclease: removal of erroneous nucleotides at the 3’ end of the new DNA strand. RNA is a Single Strand: RNA has greater freedom of movement than DNA. Can fold back on itself, forming base pairs between the complementary segments of the same strand. RNA is seldom a straight chain.
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Formation of a stem-loop structure. Base pairing between complementary sequences within an RNA strand allows the polynucleotide to fold back on itself. FROM GENES TO PROTEINS Key Concepts: F Biology Basics: Kinds of RNA: 1) Ribosomal RNA (rRNA): a component, along with proteins, of a complex molecular machine known as a ribosome. Ribosome: composed of two subunits, the small and large subunits. 2) Transfer RNA (tRNA): cloverleaf-shaped molecule that carries an amino acid on one end and an anti-codon on the other end. It transfers amino acids to the mRNA and ribosome complex. 3) Messenger RNA (mRNA): single-stranded copy of the template strand of DNA. mRNA contains codons that specify the type and order of amino acids in the polypeptide. Transcription: The process by which enzymes use one of the strands of DNA within a gene as a template to produce an mRNA. RNA has same sequence and the same 5’ 3’ orientation as the nontemplate strand of DNA. This strand is called the coding strand , and the template strand is called the noncoding strand . Coding strand: gives the sequence of the DNA to be made. Template strand: is the DNA strand used to make the RNA. Takes place in the nucleus of eukaryotic cells. Eukaryotes: any organism whose cells have a nucleus and other organelles. Primary enzyme involved is RNA polymerase . RNA polymerase: Function: to “read” the template strand of DNA and create the new RNA transcript by bonding together individual RNA nucleotides that are complementary to the DNA template. Transcription Begins at Promoters: RNA synthesis initiation requires a specific DNA sequence at a site known as a promoter , which is located near the transcription start site before the start of the gene. Transcription factors: recruit RNA polymerase to the transcription start site. DNA sequence at the promoter is recognized by these specific proteins. Transcription bubble: RNA polymerase separates the two DNA strands in a small portion of the DNA molecule creating a transcription bubble, allowing it to access the template strand & begin RNA synthesis.
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  • Winter '19
  • DNA, DNA Damage

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