BIOL130 Lecture Notes - Lecture 11: Rna Splicing, Rna Polymerase Ii, Rna Polymerase I

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1 Aug 2016
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BIOL 130 – Week Five Notes
Transcription:
-Transcription – A process catalyzed by the enzyme RNA Polymerase that
uses 1 strand of DNA as the template to synthesize a complementary RNA
sequence (sometimes called the Primary Transcript)
Genetic Code – A set of rules that specify the correspondence between nucleotide
triplets (codons) in DNA or RNA and amino acids in proteins
Template Strand – A specific sequence of nucleotides in DNA that acts as a template
to direct the synthesis of a new strand of complementary DNA (DNA that is copied
during the synthesis of mRNA)
Coding Strand - the DNA strand that has the same base sequence as the RNA
transcript produced - although T  U
-Coding strand contains codons, Non-coding strand contains anticodons
Sigma Factor - A bacterial transcription initiation factor that enables specific
binding of RNA polymerase to gene promoters; a protein needed only for the
initiation of RNA synthesis
Promoter – A nucleotide sequence in DNA to which RNA Polymerase binds in order
to begin transcription
TATA Box - A DNA sequence that indicates where a genetic sequence can be read
and decoded; A type of promoter sequence that specifies where transcription begins
to other molecules
TATA-Binding Protein (TBP) – A General Transcription Factor found about 30 base
pairs upstream of the transcription start site in some eukaryotic gene promoters
that binds specifically to the TATA Box (a DNA sequence)
General Transcription Factors – Proteins that assemble on the promoters of many
eukaryotic genes near the start site of transcription and load the RNA Polymerase in
the correct position
Ribozyme - An RNA molecule that is capable of acting as an enzyme.
RNA Polymerase II – An enzyme found in eukaryotic cells that catalyzes the
transcription of DNA to synthesize precursors of mRNA and most snRNA and
microRNA
-Precursors = A substance from which another is formed, especially by
metabolic reactions
osnRNA (Small nuclear RNA) = RNA molecules with around 200
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nucleotides involved in RNA splicing
omicroRNA = Small, non-coding RNA molecules that control gene
expression by base-pairing with specific mRNAs to regulate their
stability and their translation
mRNA (Messenger) – An RNA molecule that conveys information from the DNA to
the ribosomes and specifies the amino acid sequence of a protein (product of gene
transcription)
-Produced by RNA splicing in eukaryotes from a larger RNA molecule made by
RNA Polymerase as a complementary copy of DNA
-Is translated into protein in a process catalyzed by ribosomes
Frameshift Mutation – mutation in DNA that occurs as a result of the insertion or
deletion of a nucleotide that throws off the reading frame (3 nucleotides at a time to
code for 1 amino acid) as a result
Translocation - A chromosomal rearrangement in which a segment of genetic
material from one chromosome becomes heritably (able to be inherited) linked to
another chromosome
Wobble Hypothesis – Discovered by Francis Crick and explains why multiple
codons can code for a single amino acid.
-States that the 3rd position (3’) of the codon on mRNA and the 1st position (5’)
of the anticodon on tRNA are bound less tightly than the other pair and
therefore, offer unusual base combinations
-1 tRNA molecule (with one amino acid attached) can recognize and bind to
more than one codon, due to the less-precise base pairs that can arise
between the 3rd base of the codon and the base at the 1st position on the
anticodon
oEx. I (Inosine) can pair with A, C, or U
-4 main pairs = G-U, I-A, I-C, I-U
-There are 61 potential anticodons but only about 40 different types of tRNA
Transcriptome - The sum total of all the messenger RNA molecules expressed from
the genes of an organism.
Post-Transcriptional Modifications:
-Where Primary Transcript RNA is converted into mature (messenger RNA)
prior to protein synthesis
Methylguanosine (G) Cap – A “cap” consisting of a modified GTP (guanosine
triphosphate) that is added on the 5’ end of DNA at the beginning of transcription
and used as a recognition signal for ribosomes to bind to the mRNA.
Poly (A) Tail - A long chain of adenine nucleotides that is added to the 3’ end of an
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