A fate map of a Xenopus blastula, just before gastrulation begins, shows that the top portion of the embryo will become ectoderm (skin and nerve), the central portion will become mesoderm (bone, muscle, and blood), and the lowest portion will become endoderm (gut). How is it that the endoderm and mesoderm, shown on the outside in the fate map, end up on the inside in the embryo after gastrulation?

#Question id: 795

#Unit 1. Molecules and their Interaction Relevant to Biology

A single-stranded DNA molecule contains 40 nucleotides and has the sequence 5’-(GA)20-3’. When this single strand binds to a complementary DNA strand,

#Question id: 796

#Unit 1. Molecules and their Interaction Relevant to Biology

Which statement best describes the distinction between the purposes of the two RNAi pathways within the eukaryotic cell?

#Question id: 797

#Unit 1. Molecules and their Interaction Relevant to Biology

With respect to microRNAs, which, if any, of the following statements, is FALSE?)

A. MicroRNA genes often occur in gene clusters within introns of protein-coding genes and are usually transcribed by RNA polymerase II.

B. Like an mRNA a miRNA is initially produced as a larger precursor RNA that, like the great majority of mRNAs, usually has a 5’ cap and a poly(A) tail.

C. MicroRNAs are produced by germ-line cells only.

D. A miRNA is initially produced as a duplex RNA but in order to work it needs to be converted into a single-strand RNA.

E. MicroRNAs usually work as transcription factors.

#Question id: 798

#Unit 1. Molecules and their Interaction Relevant to Biology

Match the structural properties of DNA with the respective types of DNA in which they are found.

               COLUMN – I                                             COLUMN – II

A.        Pitch per turn of helix                                     1. 45.6 angstrom                   

                                                                                      2. 24.6 angstrom                               

 3. 33.2 angstrom

B.        Helix packing diameter                                 1. 23.7 angstrom            

                                                                                     2. 18.4 angstrom            

3. 25.5 angstrom

C.        Major-groove proportions                            1. Flattened out on helix surface

                                                                                      2. Extremely narrow but very deep

 3. Wide and of intermediate depth

D.        Minor-groove proportions                            1. Very broad but shallow

                                                                                     2. Extremely narrow but very deep

                                                                                    3. Narrow and of intermediate depth

#Question id: 799

#Unit 1. Molecules and their Interaction Relevant to Biology

The two cleavage reactions required to generate the miRNA from these primary transcripts are mediated by two distinct RNases. A characteristic of both these enzymes is that they recognize and cleave RNAs on the basis of the structure of their substrates rather than their specific sequence. Which of the following statement is INCORRECT regarding the cleavage reactions that produces a mature RNA?

#Question id: 800

#Unit 1. Molecules and their Interaction Relevant to Biology

Following table lists the two major forms of DNA duplexes, conformation of base attached to the sugar and the nature of major and minor grooves.