Following statements are regarding to gastrulation in chick embryo.

A. During gastrulation, future mesodermal and endodermal cells migrate from the epiblast through the primitive streak into the interior of the blastoderm.

B. An aggregation of cells, known as Hensen’s node, forms at the posterior end of the streak.

C. As the streak extends, cells of the epiblast move toward the primitive streak, through it, and then outward again underneath the surface to give rise internally to the mesoderm and endoderm, the latter displacing a lower layer of cells called the endoblast.

D. Cells that remain in the epiblast form the endoderm.

Which of the following statements are correct?

#Question id: 5752

#Unit 8. Inheritance Biology

#Question id: 5753

#Unit 8. Inheritance Biology

A bacterial histidine mutant was plated on minimal medium and a single colony grew. You decide to sequence the histidine biosynthetic gene of the revertant and discover that the original mutation is still present.  This colony must have been able grow due to a

#Question id: 5754

#Unit 8. Inheritance Biology

A cell is exposed to EMS (a mutagen that causes guanine to mispair with thymine) and allowed to undergo a few rounds of DNA replication.  The mutational event caused by this mutagen will be

#Question id: 5755

#Unit 8. Inheritance Biology

A researcher studying bacterial toxin predicts that a lysine within the toxin is important for binding it’s target cell.  She used site-directed mutagenesis to change a codon for lysine (AAA) to one for asparagine (AAU).  However, the mutant toxin still binds to its target cell just as well as the wild-type toxin bound and appears to have no other changes. This type of mutation is probably

#Question id: 5756

#Unit 8. Inheritance Biology

Type of mutation caused by an addition or deletion of a base in a polypeptide-encoding part of a gene

#Question id: 5757

#Unit 8. Inheritance Biology

A new E. coli mutant was tested for auxotrophy. The mutant grows on:

minimal medium (M) + arginine (A) + proline (P)

M + P + histidine (H)

M + A + H + P

but not on M or on M + A + H. The mutant requires