Assume you found a new worm species while working at Friday Harbor Marine Lab last summer. It has some cells at the vegetal pole that form right after cleavage, then move into the embryo. If you cut off the cells, the animals that developed were sterile. Using your knowledge gained from lecture, what can you tell me about what these cells might be doing? What experiments might you do to test your hypothesis? What are enhancers? How do they function to promote gene expression, especially since they may be some distance from the transcribed gene?? Do enhancers interact with promoters and basal transcription factors? Solution Lower invertebrates (including worms) develop via autonomous specification. In this type of specification, fate of cells is decided in early blastula stage. If in early stages, any cell is lost, then the organ/cell part/body part destined to be formed from that lost cell will not be formed. Such pattern of cell division and cleavage in early stages is known as mosaic division. In the above case, the new worm species isolated is a lower invertebrate. And the lost cells, are those which were responsible for formation of gonads. Now, because of autonomous specification, loss of cells, responsible for development of gonads leads to formation of sterile worms. To test the hypothesis, you can take a control animal (worm) without the \"cut off cells” and a test animal with cells cut out. Enhancers are short regions in DNA, which bind to transcription factors. Transcription factors in turn bind to promoter. So, with the help of enhancer binding of promoter, RNA polymerase and transcription factors is speeded up. Overall the process of transcription is enhanced. Enhancers can be located anywhere in the DNA. They may far away from the gene; or may be present in some other gene; or can be present in the exon itself. They can be reversed also. Enhancer of one gene can affect the transcription of another gene. There overall function is to recruit RNA polymerase to the promoter. This can be done by chromatin modeling in several ways (For detailed description of this part, please post separately). No, enhancers do not interact directly with promoters and BTFs. They interact with other transcription factors which in turn interact with a \'Transcription activator protein\'; which in turn, binds to promoter..

1. Assume you found a new worm species while working at Friday Harbor Marine Lab last
summer. It has some cells at the vegetal pole that form right after cleavage, then move into the
embryo. If you cut off the cells, the animals that developed were sterile. Using your knowledge
gained from lecture, what can you tell me about what these cells might be doing? What
experiments might you do to test your hypothesis?
What are enhancers? How do they function to promote gene expression, especially since they
may be some distance from the transcribed gene?? Do enhancers interact with promoters and
basal transcription factors?
Solution
Lower invertebrates (including worms) develop via autonomous specification. In this type of
specification, fate of cells is decided in early blastula stage. If in early stages, any cell is lost,
then the organ/cell part/body part destined to be formed from that lost cell will not be formed.
Such pattern of cell division and cleavage in early stages is known as mosaic division.
In the above case, the new worm species isolated is a lower invertebrate. And the lost cells, are
those which were responsible for formation of gonads. Now, because of autonomous
specification, loss of cells, responsible for development of gonads leads to formation of sterile
worms.
To test the hypothesis, you can take a control animal (worm) without the "cut off cells” and a
test animal with cells cut out.
Enhancers are short regions in DNA, which bind to transcription factors. Transcription factors in
turn bind to promoter. So, with the help of enhancer binding of promoter, RNA polymerase and
transcription factors is speeded up. Overall the process of transcription is enhanced.
Enhancers can be located anywhere in the DNA. They may far away from the gene; or may be
present in some other gene; or can be present in the exon itself. They can be reversed also.
Enhancer of one gene can affect the transcription of another gene. There overall function is to
recruit RNA polymerase to the promoter. This can be done by chromatin modeling in several
ways (For detailed description of this part, please post separately).
No, enhancers do not interact directly with promoters and BTFs. They interact with other
transcription factors which in turn interact with a 'Transcription activator protein'; which in
turn, binds to promoter.