In mammalian systems where the DNA polymerase does not have a 5’–3’ exonuclease activity, Okazaki fragments are connected by a two-step process. 

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#Id: 4771

#Unit 5. Developmental Biology

POP-1 activates the TBX-35 gene.

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#Id: 4772

#Unit 5. Developmental Biology

The TBX-35 transcription factor activates mesodermal genes in the MS cell, including pha-4 in the pharynx and hlh-1 in muscles.

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#Id: 4773

#Unit 5. Developmental Biology

TBX-35 inhibits pal-1 gene expression, preventing the MS cell from acquiring the C-blastomere fates.

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#Id: 4774

#Unit 5. Developmental Biology

At the 4-cell stage, the EMS cell requires a signal from its neighbor (and sister cell), the P2 blastomere.

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#Id: 4775

#Unit 5. Developmental Biology

The P2 cell produces the MOM-2 protein, a C. elegans Wnt protein.

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#Id: 4776

#Unit 5. Developmental Biology

MOM-2 is received in the EMS cell by the MOM-5 protein, a C. elegans protein Frizzled.