Describe how DNA and RNA direct cell differentiation. Give an example of how environmental factors may influence cell differentiation.

1- DNA: a specific DNA sequence encodes a transcription factor which activates the expression of target genes involved in cell differentiation  

2- RNA: short non-coding RNAs may bind to enhancer regions and thus activate the expression of target genes involved in cell differentiation  

3- Environmental factor: temperature may control the expression of genes involved in cell differentiation pathways  

Explanation:

The deoxyribonucleic acid (DNA) contains the genetic material required to encode proteins. Some of these proteins are transcription factors involved in the activation of diverse signaling pathways, including, for example, cell differentiation and proliferation. On the other hand, microRNAs (miRNAs) are short non-coding RNAs that have the ability not only to repress but also to activate transcription by binding enhancer sequences. The miRNA activation mechanism has recently been discovered. In consequence, some miRNAs may potentially activate the expression of target genes involved in cell differentiation (e.g., c-myc gene). Finally, environmental factors (e.g., nutrient availability, salinity, temperature, etc.) may also activate gene expression and thus control diverse pathways such as cell differentiation, cell proliferation and cell death (apoptosis).

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