In Drosophila, an example of position effect variegation in the fly eye. 

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#Unit 5. Developmental Biology

In regenerating planaria, β-catenin is activated in the posterior-facing blastema, which generates a tail.

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#Unit 4. Cell Communication and Cell Signaling

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#Unit 2. Cellular Organization

Detyrosylation 

tyrosine can be removed by a carboxypeptidase, where it sequentially removes the C-terminal tyrosines from α-tubulin subunits. 

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#Unit 13. Methods in Biology

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#Unit 3. Fundamental Processes

The first DNA-synthesizing enzyme to be characterized was DNA polymerase I, which is a single polypeptide of 103 kD, The chain can be cleaved into two parts by proteolytic treatment.

The larger cleavage product (68 kD) is called the Klenow fragment. It is used in synthetic reactions in vitro, It contains the polymerase and the proofreading 3'-5'  exonuclease activities.

The small fragment (35 kD) possesses a 5 '-3' exonucleolytic activity, which excises small groups of nucleotides, up to - 10 bases at a time. This activity is coordinated with the synthetic/ proofreading activity. It provides DNA polymerase I with a unique ability to start replication in vitro at a nick in DNA.