Chapter 14 Flashcards
anatomy of RNA transcripts
- untranslated regions flank protein coding region; 3’ UTR affects the stability and translation of mRNA
- Shine-Dalgrano sequence in bacteria is right upstream of the start codon and is where the ribosome binds to mRNA for translation
- protein coding region is Madde up of codons that each specify an amino acid
- introns are non-coding regions that break up coding regions (axons) in eukaryotes
transcription and translation are ______ in eukaryotes
uncoupled
where does transcription and translation happen in eukaryotes?
transcription happens in the nucleus, translation happens in the cytoplasm
pre-mRNA
needs modification before its mature mRNA
what are some modifications of mRNA?
addition of 5’ cap
addition of 3’ poly A tail
splicing out of introns
alternative processing
RNA editing
addition of 5’ cap
guanine is added to the 5’ end of mRNA and is methylated
helps with mRNA stability, ribosome binding, and intron removal
addition of 3’ poly A tail
50-250 adenine nucleotides on 3’ end
helps with mRNA stability, ribosome attachment, and mRNA export to cytoplasm
splicing of introns
consensus sequences at exon/intron junctions and internal branch point guide splicing
spliceosome= RNA and proteins
alternative splicing
different combos of exons retained and spliced together
6-exon gene and 4-exon mRNA in thyroid cells makes calcitonin protein that regulates calcium levels
same 6-exon gene and 5-exon mRNA in brain cells makes CGRP protein that helps with pain transmission and blood vessel dilation
***different splicing can lead to differentiation of cells and function
what is alternative processing and what are the 2 ways to do it?
makes different proteins from the same gene
1. alternative splicing
2. multiple 3’ cleavage sites
multiple 3’ cleavage sites
proteins of different lengths can be produced from one gene
what does alternative processing effect?
can happen in 90% of human genes, can vary between people, and contributes organismal complexity
RNA editing
guide mRNA changes sequence of mRNA message
tRNA
each tRNA is specific for a different amino acid
incorporates rare modified bases
75-95 nt in length
processed after transcription
cloverleaf tertiary structure of tRNA
amino acid attachment site has conserved sequence where amino acid binds
anticodon is 3 nt long and interacts with codon in mRNA
aminoacyl-tRNa synthetase enzymes pair tRNA with the correct amino acid
*acceptor stem at one end, anticodon at the other end