Transcript 25 transcription, translation

Using DNA
-Transcription
- RNA processing
- Universality of the genetic code
- Translation
Refer to chapter 12.3 to 12.6, and 13.2, 13.3 in text.
There are enzymes that can make proteins (nonribosomal peptides)
without this process:
Those are enzyme-specific,
and not what we are talking about here.
Review DNA structure
(What does it look like?)
and RNA structure.
Recap DNA replication
(Unzipping the... helix, etc.)
So... what do you recall/know about transcription and translation?
purpose? location? general mechanisms?
Now go to animations.
TRANSCRIPTION/mRNA PROCESSING
Transcription and processing only
https://www.youtube.com/watch?v=LPnz1i0Fr98
Also to processing only
https://www.youtube.com/watch?v=eMYl0wjNc0U
‘realistic”
https://www.youtube.com/watch?v=5MfSYnItYvg
You can also go to Crash Course or Bozeman of course
transcription:
DNA to RNA
… that promoter thing isn’t as simple as the previous picture suggests!
http://www.google.com/imgres?imgurl=http://biology.kenyon.edu/courses/biol114/Chap10
(You don’t need to worry about this.
I just don’t want you to think you are responsible for everything!
There will still be stuff to learn in college!)
processing of
pre-mRNA:
5’ cap, poly(A) tail ↑,
and excision of introns →,
leaving exons to move
out of the nucleus…
Some pre-mRNA are processed
to include different exons One gene can code for multiple proteins.
Some introns become microRNAs (miRNA)
that impact translation…
Are you accessing the
IB syllabus at the
Stanton web site?
Transcription and RNA processing terminology
(Read all as bold and underlined.)
initiation
promoter
transcription factor
elongation
5’ to 3’
RNA polymerase
transcription unit
termination
terminator
termination point
sense strand
antisense (template) strand
pre-mRNA
leader
trailer
intron
exon
snRNPs
spliceosome
5’ cap
poly A tail
mRNA
So now the message can leave the engineering library
and go out onto the factory floor.
The ‘factory’ has 20 amino acids,
while the plans only have 4 nucleotides....
Genetic Code
Deciphered by
Marshall Nirenberg, 1966.
Note
- how table is read.
- what it represents
(RNA codons).
- start codon
- stop codons
- redundancy:
most amino acids have
multiple codons…
(ramifications?)
What amino acid does
UGU code for?
What is the codon
for alanine?
What is a DNA sequence for
met-ser-his?
What a.a. sequence from
TCAGGAACAATTTAG?
Same code, different presentation
(Some tables have the DNA rather than the RNA sequences.)
Code is almost universal
- exceptions usually mitochondrial
- often involve a.a. for stop codon(s)
- may swap in more stops
- novel amino acids:
usually in prokaryotes
pyrrolysine for UAG
selenocysteine for some UGA
(25 of your proteins have this last one!)
http://www.biology.lsu.edu/heydrjay/1201/Chapter17/SCI_Amino_Acid_CIRCLE.jpg
go to an animation
for translation…
TRANSLATION
“Basic”, but fairly complete…
https://www.youtube.com/watch?v=8dsTvBaUMvw
Virtual Cell
https://www.youtube.com/watch?v=5bLEDd-PSTQ
Realistic view
https://www.youtube.com/watch?v=TfYf_rPWUdY
translation:
from the language of nucleic acids,
into that of protein.
nobelprize.org/.../medicine/dna/a/translation/
↑
NB
close-up of tRNA →
aminoacyl-tRNA synthetase ↓
←NB
www.nsf.gov/news/overviews/biology/interact05.jsp
This is happening on rER ↑
if the proteins are for export or are lysozymes;
Local proteins are made on free ribosomes.
The shift from the A to P site is translocation.
Recall the peptide bond… and be able to draw it. →
The energy required for the formation of
one peptide bond includes the hydrolysis of
2 ATP and 2 GTP molecules.
Regulation of gene expression in eukaryotes
chromatin structure
methylation/acetylation of histone tails,
epigenetics, inherited factors
transcriptional control
methylation of cytosines blocks reading
role in cell specialization
see also slide 4
posttranscriptional control
alternate splicing
control of mRNA exiting nucleus
translational control
persistence of 5’ cap and poly-A tail
microRNA from introns → RISC
(RNA-induced silencing complex)
posttranslational control
tertiary structure,
prosthetic groups?
coenzymes?
proteases? lifted from p. 237 in Mader
Different genes coordinate whole structures
Pax6 (eyes), Tbx5 (limbs), Hox (body shape)
Translation terminology (Read all as bold and underlined.)
initiation
mRNA
codon
start codon
tRNA
amino acid
CCA tail
(amino acid binding site)
tRNA-activating enzyme
(aminoacyl-tRNA synthetase)
anticodon
ribosome
rRNA
ribosomal protein
nucleolus
small ribosomal subunit
mRNA binding site
elongation
large ribosomal subunit
A, P and E sites
translocation
5’ to 3’ (reverse relative to DNA)
polysome
termination
stop codon
What is meant by the genetic code?
How is it “universal”?
What are the three stages of DNA to protein?
Where does each occur?
Walk through each.
There were 4 different RNAs involved:
Identify each along with its use.
Give examples of form fitting function,
for ribosomes and tRNA.
Lots of proteins…
Investigate any for which the name
does not obviously lead to the job.
transcription
intron
CCA tail
initiation
exon
amino acid binding site
promoter
snRPs
tRNA-activating enzyme
transcription factor
spliceosome
aminoacyl-tRNA synthetase
elongation
5’ cap
anticodon
5’ to 3’
poly A tail
ribosome
RNA polymerase
mRNA
rRNA
transcription unit
start codon
ribosomal protein
termination
nucleolus
terminator (Arnold)
redundancy
small ribosomal subunit
termination point
The Genetic Code
mRNA binding site
sense strand
translation
elongation
antisense strand
translocation
large ribosomal subunit
pre-mRNA
initiation
A, P and E sites
leader
codon
polysome
trailer
tRNA
termination
amino acid