Transcription Packet #21 12/8/2018 12:59 PM

Introduction The process by which information encoded in DNA specifies the sequences of amino acids in proteins involves two steps Transcription RNA molecule, complementary to the DNA template strand, is synthesized Only one strand of DNA is used during transcription Translation More to come later 12/8/2018 12:59 PM

RNA RNA molecules are single-stranded Ribonucleic Acid Composed of RNA nucleotides Phosphate Sugar Ribose Nitrogenous Bases Purines Adenine Guanine Pyrimidines Cytosine Uracil RNA molecules are single-stranded DNA molecules are double-stranded 12/8/2018 12:59 PM

Types of RNA Messenger RNA Contains information that specifies the amino acid sequence of polypeptide chains Serves as the template for protein synthesis 12/8/2018 12:59 PM

Types of RNA Small nuclear RNA Transfer RNA Ribosomal RNA Class of RNA molecules that transport amino acids to ribosomes for incorporation into a polypeptide undergoing synthesis. “Transporter” Ribosomal RNA RNA that make up ribosomes. Small nuclear RNA RNA found in the enzyme spliceosome More to come later 12/8/2018 12:59 PM

Genes The Review Where are genes located? On the DNA strand that makes up the chromosome What is the name of the location on the chromosome where genes are located? The Locus What are genes composed of? DNA nucleotides

Regions of the Gene I Regulatory Region The Coding Region This is where RNA Polymerase, the only enzyme used during transcription, binds on the DNA strand The Regulatory Region has a region known as the Promoter Region The TATA Box is found in the Promoter Region Location where RNA Polymerase binds and unzips the DNA molecule The Coding Region Area where RNA nucleotides are joined together to make an RNA strand. The end of the coding region is called the terminator.

RNA Polymerase Only enzyme used during transcription. However, there are three variations of the enzyme— depending on the type of RNA being produced RNA Polymerase I Transcribes rRNA genes RNA Polymerase II Transcribes protein coding (mRNA) genes RNA Polymerase III Transcribes other functional RNA genes tRNA 12/8/2018 12:59 PM

Transcription Step by Step Location Nucleus RNA Polymerase binds at the promoter region (sequence) and unzips the DNA strand 12/8/2018 12:59 PM

Transcription Step by Step RNA Polymerase works downstream and reaches the coding region. When in the coding region, RNA polymerase adds RNA nucleotides to the 3’ end of the newly formed RNA strand New RNA strand ONLY grows in the 5’ to 3’ direction 12/8/2018 12:59 PM

Transcription Step by Step RNA Polymerase hits the “Terminator” sequence that signals the end of transcription Newly made RNA is released The New RNA strand is called pre-mRNA Why? Because the pre- mRNA needs to be “groomed” for the BIG moment--Translation 12/8/2018 12:59 PM

Sections of pre-mRNA Contains introns and exons. Introns Exons The “Junk in the Trunk” Regions of the RNA strand that must be removed, via splicing, and will not be used during translation Exons Regions of RNA that WILL be used and translated into amino acids during TRANSLATION 12/8/2018 12:59 PM

Splicing Eukaryotic Cells Removal of introns Location Nucleus of the Cell Enzyme used is Spliceosome Removes the introns via “cut & paste” After splicing, the pre- mRNA will be officially known as mRNA mRNA leaves the nucleus, through the nuclear pores, and enters the cytoplasm 12/8/2018 12:59 PM

mRNA Transcription & Translation 12/8/2018 12:59 PM