In some rare salamander species, all individuals are females. Reproduction relies on those females having access to sperm from males of another species. However, the resulting embryos receive no genetic contribution from the males. Why do you think sperm are necessary for reproduction?

#Question id: 2908

#Unit 2. Cellular Organization

The H3.H4 tetramers and H2A.H2B dimers each interact with a particular region of the DNA within the nucleosome. Which of the following statement is CORRECT regarding the characteristic binding of histones with the DNA?

I. Of the 147 bp of DNA included in the structure, the histone-fold regions of the H2A.H2B dimer interact with the central 60 bp.

II. Histone H3.H4 tetramers occupy a key position in the nucleosome by binding the middle and both ends of the DNA.

III. The amino-terminal region of H4 most proximal to the histone-fold region forms a fourth alpha helix that interacts with the final 13 bp at each end of the bound DNA.

IV. The H3.H4 tetramer associate with approximately 30 bp of DNA on either side of the central 60 bp of DNA bound by H2A.H2B dimer.

V. The two H2A.H2B dimers form the bottom part of the histone octamer located across the disc from the DNA ends.

#Question id: 18901

#Unit 13. Methods in Biology

#Question id: 4239

#Unit 3. Fundamental Processes

Use the figure to answer the question. What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?

#Question id: 11752

#Unit 7. System Physiology – Animal

Which of the following substances enhances the sensitivity of pain receptors but does not directly excite them?

#Question id: 5806

#Unit 8. Inheritance Biology

Which of these is NOT a mechanism by which a chromosome rearrangement could affect gene function?