BIOL 1010U Lecture Notes - Lecture 5: Messenger Rna, Central Dogma Of Molecular Biology, Transfer Rna

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21 Jun 2018
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BIOL1010 and BIOL1011 - Lecture 5
- Nucleic Acids Encoding Information and Transcription -
Assigned Readings in Textbook:
Chapter 3 (section 3.3) – Retrieval of Genetic Information stored in DNA: Transcription (pages 58 to 63)
-DNA carries genetic info for proteins that are synthesized on ribosomes – located in cytoplasm in
eukaryotes
-Genetic info is transferred from DNA to ribosomes
-RNA retrieves info from stored in DNA for use in protein synthesis
-Transfer from DNA to RNA constitutes from key step in transcription in central dogma
-RNA is a polymer linked by phospodiester bonds – each strand has polarity – determined by what end
carries the hydroxyl and what end carries the phosphate
-Hydroxyls – reactive functional groups – makes RNA less stable
-RNA uses ribose sugar and has the base uracil
-DNA unwinds – one strand becomes template strand – for synthesis of RNA transcript – produced by
polymerization of ribonucleoside triphosphate
-Enzyme that carries out polymerization – RNA polymerase
-Nucleic acids grow in a 5’ to 3’ direction – DNA template and RNA strand transcribed are antiparallel –
DNA runs opposite from RNA
-Promoter region – where RNA polymerase bind to DNA duplex – contain sequence similar to 5’-TATAA-
3’ (TATA box)
-Transcription continues until it encounters sequence known as terminator – then transcript is released
-Transcribed portion – based on position of promoter
-Eukaryotes – requires at least six proteins (general transcription factors) – also needed is one or more
types of transcriptional activator proteins – binds to specific DNA sequence (enhancer)
-Can attract mediator complex – recruit’s RNA polymerase – in eukaryotes – protein-coding gene
responsible is pol II – once in place transcription begins (initiation)
-Next is elongation – growing end of RNA is paired with template strand (RNA-DNA duplex)
-Polymerization reaction – releases phosphate-phosphate group (pyrophosphate)
Chapter 3 (section 3.4) – Fate of the RNA Primary Transcript (pages 63 to 66)
Use the following wireframe outline to make notes on the content presented in Lecture 5
Refer to Chapter 3 - sections 3.3 and 3.4 (pages 58 to 66) in your textbook and the Chapter 3
resources on LaunchPad to supplement your notes and aid in studying this material
1. What is meant by the “Central Dogma”?
Francis Crick’s central dogma stated: DNA codes for RNA and RNA codes for protein
Links everything together and tells us about the structure and function
Tells us that DNA is capable of being replicated/copied – DNA synthesis (chapter 12)
2. What two processes are involved in retrieving the information stored in the DNA molecules?
(1) Messenger RNA - mRNA
(2) Transfer RNA - tRNA
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3. What is transcription?
Transcription and translation work in two steps
Messenger RNA – mRNA – carries instructions for making polypeptides from DNA in nucleus into
cytoplasm, where it serves as a template for polypeptide synthesis
Transfer RNA – tRNA – links the code of mRNA and the code for specifying correct sequence of
amino acids in polypeptides
LaunchPad animation for chapter 4
Transcribes info in same language from DNA to RNA
Translates info from nucleotide language (in RNA) to amino acid language (in proteins)
General process of transcription is straightforward – as region of DNA helix unwinds, one strand
is used as the DNA template for the RNA transcript to be made – requires an enzyme (RNA
polymerase)
DNA template strand unwinds 3’ to 5’ – new RNA transcripts 5’ to 3’
4. What is a gene?
Expression of a gene = sequence of DNA nucleotides
1. Transcription – makes single-stranded mRNA copy of sequence of DNA nucleotides
(gene)
Writes a copy of instructions – uses complementary base pair
Each chromosome is a gene – can have many genes in each
23 thousand genes
Human genome
Has info to make polypeptide chain of amino acids (proteins)
Translation – takes instructions encoded in mRNA “copy” and “translate” them into a new
language (tRNA with amino acids) that can make a polypeptide chain (protein)
Way of protecting things and storing important in
Uses language of genetic code
5. What are the three steps in transcription?
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Document Summary

Nucleic acids encoding information and transcription - Chapter 3 (section 3. 3) retrieval of genetic information stored in dna: transcription (pages 58 to 63) Dna carries genetic info for proteins that are synthesized on ribosomes located in cytoplasm in eukaryotes. Genetic info is transferred from dna to ribosomes. Rna retrieves info from stored in dna for use in protein synthesis. Rna is a polymer linked by phospodiester bonds each strand has polarity determined by what end. Transfer from dna to rna constitutes from key step in transcription in central dogma carries the hydroxyl and what end carries the phosphate. Hydroxyls reactive functional groups makes rna less stable. Rna uses ribose sugar and has the base uracil. Dna unwinds one strand becomes template strand for synthesis of rna transcript produced by polymerization of ribonucleoside triphosphate. Enzyme that carries out polymerization rna polymerase. Nucleic acids grow in a 5" to 3" direction dna template and rna strand transcribed are antiparallel .

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