The H3.H4 tetramers and H2A.H2B dimers each interact with a particular region of the DNA within the nucleosome.

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

II. The amino-terminal region of H3 most proximal to the histone-fold region forms a fourth a-helix that interacts with the final 13 bp at each end of the bound DNA.

III. The relatively short length of DNA bound by H2A.H2B dimers is sufficient to prepare the DNA for H3.H4 tetramer binding.

IV. The H3.H4 tetramer forms the bottom part of the histone octamer located across the disc from the DNA ends whereas two H2A.H2B dimer occupies the top part.

Which of the following represents the correct binding of the histones with the DNA?

#Question id: 5036

#Unit 5. Developmental Biology

 The experiments of Spemann and Mangold first defined what feature of amphibian embryos?

#Question id: 13132

#Unit 10. Ecological Principles

Biologists performed an experiment with flies to examine the effects of population size on the maintenance of genetic variation  and  on  egg-to-adult survival.  From  a  large  source  population, they  randomly  assigned  eggs  to  three experimental  populations  of  size  N,  equal  to  20,  60,  and0100.  For  later  generations,  they  collected  N  eggs  from each  population  and  moved  them  into  identical  vials  that  co0ntained  f2re0sh  me4d0ium.  Th6e0y  coun8te0d  the  number  of adult flies that emerged and used tissue samples from the adults for genetic analyses. Genetic variation was measured by  scoring  alleles  at  several  polymorphic  loci  and  expressed  as  the  average  number  of  alleles  at  those  loci.  The results are summarized in Figure 1 and Figure 2 below.

Which other process appears to have substantially influenced the outcome of this experiment? 

#Question id: 15168

#Unit 2. Cellular Organization

#Question id: 13156

#Unit 2. Cellular Organization

#Question id: 5688

#Unit 8. Inheritance Biology

Which of the following are not cause of aneuploidy