BIOL 1000 Chapter Notes - Chapter 13: Transfer Rna, Base Pair, Frameshift Mutation
29 Jun 2018
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CHAPTER 13: Gene Structure & Expression
13.1 Connection Between DNA RNA Protein (Central Dogma)
First, Garrod studied alkaptonuria (black urine) relating genes&metabolism,
and second, Beadle & Tatum did genetic experiments with Neurospora
crassa relating genes&enzymes using arg genes; one gene/one polypeptide
hypothesis: direct correspondence between gene mutations and alterations
of polypeptides.
Transcription: sequence of nucleotides in DNA is copied into a
complementary sequence in an RNA molecule.
Translation: sequence of nucleotides in mRNA specifies AA sequence for
polypeptide.
Prokaryotes can do them at same time, we can’t.
Genetic code/triplet code: nucleotide info that specifies AA sequence of
polypeptide; made of 3-letter code (codon). AUG (methionine) at beginning
of coded message establishes reading frame for reading codons
(start/initiator codon). Stop codons/nonsense/termination: UAA, UAG,
UGA indicate end & don’t specify an AA, while other 61 codons do. 3
nucleotides at a time; degeneracy (redundant – most aa’s other than
methionine & tryptophan are encoded by more than one codon) & universal.
Other genes also code directly for RNA but aren’t translated like mRNA;
e.g. tRNA, RRNA, snRNA. *Note: template strand is always read 3’ to 5’,
& mRNA is made 5’ to 3’
13.2 Transcription: DNA-Directed RNA Synthesis: process by which info coded
in DNA is transferred to complementary RNA copy. TATA box in promoter
initiates transcription, & transcription unit is the part of gene copied into RNA.
1) Initiation: Begins when transcription factors & RNA polymerase II bind to
promoter (control sequence for transcription) TATA area in DNA & starts
synthesizing an RNA.
2) Elongation: RNA polymerase II adds RNA nucleotides in sequence
according to DNA template, unwinding DNA as it goes & behind it, DNA
strands reform into double helix.
3) Termination: at end of transcribed sequence, the transcript & polymerase
leave DNA template. In eukaryotes, pre-mRNA has been made which will
create mRNA.
Difference in eukaryotes & bacteria: promoter sequences differ; in eukaryotes
RNA polymerase II doesn’t bind to DNA directly and instead binds to promoter
once transcription factors have, while in bacteria it does. Also, eukaryotes don’
have a transcription terminator signalling the end, while bacteria has 2 types: one
find more resources at oneclass.com
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Document Summary
13. 1 connection between dna rna protein (central dogma) First, garrod studied alkaptonuria (black urine) relating genes&metabolism, and second, beadle & tatum did genetic experiments with neurospora crassa relating genes&enzymes using arg genes; one gene/one polypeptide hypothesis: direct correspondence between gene mutations and alterations of polypeptides. Transcription: sequence of nucleotides in dna is copied into a complementary sequence in an rna molecule. Translation: sequence of nucleotides in mrna specifies aa sequence for polypeptide. Prokaryotes can do them at same time, we can"t. Genetic code/triplet code: nucleotide info that specifies aa sequence of polypeptide; made of 3-letter code (codon). Aug (methionine) at beginning of coded message establishes reading frame for reading codons (start/initiator codon). Uga indicate end & don"t specify an aa, while other 61 codons do. 3 nucleotides at a time; degeneracy (redundant most aa"s other than methionine & tryptophan are encoded by more than one codon) & universal.
