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Cytoplasmic Determinants/Signal Induction

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Cytoplasmic Determinants/Signal Induction

Postby lychee » Thu May 13, 2010 2:24 am

Hi all, I've got an assignment for a first year course I would like to go over....if anyone has any feedback on my answers it would be greatly appreciated! Thx :wink:


4.)Answer the following questions: (6 marks)

a.) What are cytoplasmic determinants, and how are they distributed in the egg?

Cytoplasmic determinants are the substances in the maternal gamete that affect the course of early development by regulating gene expression which influences the fate of the cells. These molecules of mRNA, proteins, and other substances and organelles are distributed randomly and unevenly across the egg. This is significant because after the egg is fertilized, the nuclei that results from mitotic division is then exposed to different cytoplasmic environments.

b.) What is the source of signal molecules (inducers)?

Signal molecules come from embryonic cells themselves. Embryonic cells send signal molecules to other nearby embryonic cells to alter their gene expression.

c.) What is signal induction?

Induction is the process in which these signal molecules cause changes in the target cells. Because the signal molecules generally induce changes in the gene expression of nearby embryonic cells, this interaction results in the differentiation into specialized cells that make up a new organism. Induction can occur through either the diffusion of chemical signals that come into contact with target cells or by cell surface interactions if the cells are touching one another.

d) Outline how cytoplasmic determinants and signal induction can influence transcription and the ultimate expression of genes.

Cytoplasmic determinants influence transcription because their uneven distribution sets up gradients that determine the orientation of the cell (for example, which side is the “head” or which side is the “tail”). Where these gradients are located determines the location certain proteins are transcribed and translated. Additionally, embryonic cells can induce transcription factors, which initiate transcription, onto other embryonic cells. Together, cytoplasmic determinants and signal induction determine the pattern formation of organisms by influencing genetic expression.
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Postby JackBean » Thu May 13, 2010 8:28 am

d) the cells usually do not have "heads" and "tails" ;) The organism/organ/tissue can have...
And even if they had, not in the case of transcription and translation...
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby lychee » Sat May 15, 2010 7:02 pm

Ok cool, thanks for the feedback Jack Bean.

I've changed that sentence to...
"Cytoplasmic determinants influence transcription because their uneven distribution sets up gradients that determine the orientation of the cell (for example, which area will develop into tissues that become a certain body part)."
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