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You are looking at lampbrush chromosomes, named because they look covered in bristles. At this stage of development, the chromosomes decondense--stop being so tightly packed--and the individual strands of DNA are quite accessible to enzymes. As you are watching, the enzyme RNA polymerase is "walking" along the genes, making RNA copies in the process of transcription. While we can't actually see the RNA at this magnification, you can see the loops of DNA wiggling in the liquid culture medium. During oogenesis (the process of making an egg) one of the most important jobs to be done is stockpiling materials that will be needed during early development, once fertilization occurs and an embryo is formed. Lampbrush chromosomes represents an elegant way eggs have evolved to transcribe tremendous amounts of messenger RNA molecules, which are used during early development to make the huge numbers of proteins necessary for cell division and differentiation.

We were very, very lucky this year to learn how to isolate lampbrushes from Dany Adams, a professor of Biology at Smith College. Our entire Bio 305 class trooped over to her lab, where she graciously and humerously taught us all we needed to know about dissecting oocytes, finding nuclei, and encouraging chromosomes to gently drift down onto a coverslip for viewing.

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