Transcription Flashcards
Gene Expression
The process by which DNA directs the synthesis of proteins
Transcription
What direction is DNA read in transcription?
The synthesis of mRNA using information in the DNA.
DNA is always read in 3’ to 5’ orientation.
mRNA
messengerRNA carries a genetic message from the DNA to the protein-synthesizing machinery of the cell
Ribosomes
The site for protein synthesis in the cell. Messenger RNA is translated here.
Primary Transcript
Pre-mRNA? The initial RNA transcript from any gene.
Codon
The triplet of mRNA nucleotides used to code for Amino Acids
Template Strand
The strand used by RNA Polymerase as a TEMPLATE for the mRNA to be built from 5’ to 3’.
Reading Frame
The reading frame is the sequence of mRNA that gets translated into amino acids. It starts from the START codon AUG and ends at the stop codons. UAA, UAG, UGA.
RNA Polymerase
Does RNA polymerase need a primer?
The enzyme that pries the DNA strands apart and joins RNA nucleotides complementary to the template strand.
RNA Polymerase does not need a primer like DNA Polymerase does
Promoter
Sequence? Why this sequence?
The DNA sequence where RNA polymerase attaches
TATA Box. It’s easy to open because less H-bonds
Terminator
The sequence that signals the end of transcription
This is only for bacteria
Transcription Unit
The portion of DNA downstream from the promoter. This is what is transcribed.
Transcription Factor
Transcription Factors are proteins that bind to the DNA before RNA polymerase II can bind to the promoter.
5’ Cap & Poly-A tail
The 5’ Cap is added to the 5’ end of the pre-mRNA during RNA processing and is composed of a modified guanine nucleotide. The Poly-A tail is a series of 50-250 Adenine nucleotides added to the 3’ end of the pre-mRNA during RNA processing.
They both function to facilitate the export of the mature mRNA from the nucleus and protect it from degradation by hydrolytic enzymes. Also, they help ribosomes attach to the 5’ end.
RNA Splicing
This is the process during RNA processing where Introns are cut out and exons are joined together by spliceosomes
Introns/Exons
Introns are the portion of the mRNA that is cut out and does not code for anything. Exons are expressed (not completely sometimes).
Genotype vs. Phenotype?
An organism’s genotype is carried in its sequence of bases.
The phenotype is a consequence of the proteins that are expressed.
How is transcription and translation different in prokaryotes when compared to eukaryotes?
Because bacteria lack nuclei, transcription and translation can occur simultaneously. There is also no RNA processing in bacteria.
Start Codon: Sequence? Function? AA?
The START Codon says when to start reading the mRNA molecule. Its sequence is AUG and is also the amino acid methionine.
What are the three processes in transcription and how do they work?
- Initiation. Transcription factors bind to the TATA box (promoter) and RNA polymerase recognizes this and binds to it. RNA polymerase II bound to the transcription factors is known as the transcription initiation complex.
- Elongation. RNA Polymerases move along the DNA and untwist the double helix while elongating the mRNA strand.
- Termination. The polymerase falls off the DNA and the mRNA floats away.
