Chapter 17 (6)
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__share many aspects of the mechanisms of gene expression with eukaryotes, as well as a few with bacteria.
Recent advances in molecular biology have enabled researchers to determine the complete nucleotide sequences of hundreds of genomes, including many genomes from each domain. With this, we can compare gene and protein sequences with domains.
Bacterial and eukaryotic __ differ significantly from each other. In contrast, the single __of Archaea resembles the three eukaryotic __, and Archaea and eukaryotes use a complex set of __, unlike bacteria.
- RNA polymerases
- RNA polymerase
- RNA polymerases
- transcription factors
__is terminated differently in bacteria and eukaryotes. The achaeal way may be more like the eukaryotic process.
The most important differences between bacteria and eukaryotes with regard to gene expression arise from the bacterial cell’s relative absence of __.
· A bacteria cell ensures a streamlined operation. In the absence of a nucleus, it can simultaneously __ and __ the same gene and the newly made protein can quickly diffuse to its site of function.
- compartmental organization
- transcribe and translate
Many believe the Archaea process is the same as in bacterial, because they lack a __.
In contrast, the eukaryotic cell’s __ segregates transcription from translation and provides a compartment for extensive __. This processing stage includes additional steps whose regulation can help coordinate the eukaryotic cell’s elaborate activities.
- nuclear envelope x2
- RNA processing
True or False:
Finally, euk. cells have complicated mechanisms for targeting proteins to the appropriate cellular compartment (organelles)
There are many new definitions for a gene.
The statement that a gene codes for a __is too simple. Most euk. genes contain __, so large portions of these genes have no corresponding segments in polypeptides.
- noncoding segments (introns),
Molecular biologists also often include __and certain other regulatory regions of DNA within the boundaries of a gene. The __ are not transcribed, but they must be present for transcription to occur.
True or False
Our molecular definition of a gene must also be broad enough to include the DNA that is transcribed into rRNA, tRNA, and other RNAs that are not translated. These genes have no polypeptides, but play crucial roles in the cell.
What is the new gene definition?
A gene is a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule.
__ bring about an organisms observable phenotype.
A given type of cell expresses only a subset of its genes.
This is an essential feature in multicellular organisms.
__ is precisely regulated.
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