Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief ________.

TLS Online TPP Program

#Question id: 5220

#Unit 11. Evolution and Behavior

In comparing the genomes of humans and those of other higher primates, it is seen that humans have a large metacentric pair we call chromosome #2 among our 46 chromosomes, while the other primates of this group have 48 chromosomes and any pair like the human #2 pair is not present; instead the primate groups each have two pairs of midsize acrocentric chromosomes. What is the most likely explanation?

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#Question id: 1694

#Unit 4. Cell Communication and Cell Signaling

Antigen processing for presentation by MHC class II molecules involves:

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#Question id: 2057

#Unit 4. Cell Communication and Cell Signaling

Lymph nodes and the spleen are the most highly organized secondary lymphoid organs. T-cell and B-cell activity are separated into distinct microenvironments in both. T cells and B cells  are found in

TLS Online TPP Program

#Question id: 26469

#Unit 3. Fundamental Processes

RNA proofreading and backtrack in the prokaryotes is done by

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#Question id: 12909

#Unit 13. Methods in Biology

According to the diagram, arrange the steps in correct order: 

1. DNA is then digested by the Cas9 nuclease at specific points on both DNA strands. 

2. Homologous recombination to repair the break and incorporate the new DNA sequence then follows. 

3.The nuclease Cas9 is targeted to DNA by a guide RNA consisting of a specific 20 nucleotide spacer/targeting sequence (crRNA).

 4. That identifies the DNA to be modified, linked to a trans-activating (tracrRNA) sequence necessary for the recruitment and stability of Cas9 nuclease.