Which of the following BEST encapsulates the findings of the Hozumi and Tonegawa experiments?
A. Every possible light chain that could be formed, in terms of receptor specificity, is encoded by a separate gene within the human genome.
B. Light chains are produced by means of somatic rearrangement of germ-line DNA in B cells.
C. The different light-chain variable regions are produced by means of alternative splicing of pre-mRNA that has been transcribed from a fixed, unchanging DNA sequence.
D. Different light chains, each with unique specificity, are produced via the activity of alternative transcription factors that regulate antibody production at the level of transcription initiation.
E. None of the above
Answer: B
Biology
- Which of the following statements about adaptive radiation is correct?
- Which organisms are not examples of an adaptive radiation?
- How long ago do scientists believe life first began on Earth?
- What process produces Earth's atmospheric oxygen?
- What evidence points to the date of the appearance of the first oxygen-producing organisms?
- Which of the following best describes the archaeans described in the video?
- The red sedimentary rocks of Western Australia resulted from the combination of oxygen and _____.
- Achaeans can tolerate which of the following extreme habitats?
- Animals first appeared during the _____.
- The Cenozoic era began approximately _____ million years ago.
- ____ were the dominant vertebrate life form during the Mesozoic era.
- Most modern animal phyla evolved during the _____ era.
- Bony fish first evolved during the _____ .
- Life arose during the _____.
- Flowering plants first appeared during the _____.
- The Mesozoic era began approximately _____ million years ago.
- The Precambrian time began at least _____ million years ago.
- Seed plants first appeared during the _____.
- The first prokaryotic cells appeared during the _____.
- Reptiles first appeared during the _____ era.
- We are living during the _____era.
- Dinosaurs went extinct during the _____.
- _____ were the dominant vertebrate life form during the Paleozoic era.
- You are given an unknown organism to identify. It is unicellular and heterotrophic. It is motile, using many short extensions of the cytoplasm, each featuring the 9 + 2 filament pattern. It has well-developed organelles and three nuclei, one large and two small. This organism is most likely to be a member of which group?
- Reinforced, threadlike pseudopods that can perform phagocytosis are generally characteristic of which group?