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The DNA in a bacterial virus – enormous condensation is needed for the virus head to accomodate all its DNA. In Escherichia coli the DNA is about 1 med mer long, while the cell is close to 1 μ m. Here the DNA information also has to be read!.
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The DNA in a bacterial virus – enormous condensation is needed for the virus
head to accomodate all its DNA.
close to 1 μm. Here the DNA information also has to be read!
1 m! This requires very ”advanced” methods of
packaging to both have enough space in the nucleus
and at the same time allow reading of the information
DNA in eukaryotes (but not in bacteria and Archae) is twisted around protein
complexes called histones. They are positively charged proteins that interact
with the negatively charged DNA. Each ”ball” is called a nucleosome.
The Central Dogma – this is probably the most important slide in the course!
A gene is the same as a segment of DNA that after transcription and translation gives rise to a specific protein (polypeptide chain). You may also see the word cistron used. It is in practice the same as gene.
in E. coli. The process is
much more complex
in eukaryotes in that
proteins are involved
may or may not be present
The transcript has the same sequence as the non-template strand except that
T is substituted by U.
There are many transcription factors in bacteria, and the numbers vary a lot
between species. In eukaryotes there are an enormous number of such factors.
Several genes can be transcribed as a unit in bacteria. This is not common in
eukaryotes. Such a unit (cluster of cotranscribed genes) is called an operon.
Transcription in eukaryotes is much more complex than in bacteria, partly
because many more protein factors are involved
Transcripts in eukaryotes are heavily modified after transcription, by capping,
polyadenylation and splicing
encodes the corresponding protein
Splicing may occur in different ways, so that several different proteins are made
from one specific mRNA. The varying processes may takwe place in different
tissues of a body.
Introns are spliced ourt by autocatalysis or protein-assisted catalysis. NB! This
shows that RNA alone can be catalytic (acts like an enzyme).