PART C questions for CSIR NET Life Sciences
Developmental Biology
- A gap gene mutation might cause which of the following defects in the embryonic body plan?
(1) every other segment would be missing, resulting in T1, T3, A2, A4, etc. but no T2, A1, A3, and so on.
(2) segments A2 through A6 would be missing, but the rest of the pattern is essentially normal
(3) no segmentation would be evident
(4) patterning within each segment would be abnormal, causing for example denticle belts to form across the entire segment
2. The activation of zygotic hunchback expression by Bicoid protein illustrates what principle in the establishment of positional information in embryos?
(1) the mother can influence development through the packaging of materials into the egg
(2) a gradient of a protein can activate a gene in a discrete region of an embryo through a threshold effect
(3) the identity of segments in the embryo is a reflection of their position in the embryo
(4) a cascade of gene activations occurs in the syncitial blastoderm
3. In which portion of the frog’s life-cycle would a frog appear most similar to a mammal?
(1) the fertilized eggs of frogs and mammals are similar in size and look nearly identical
(2) a frog blastula is very similar to a mammalian blastocyst
(3) the events of gastrulation in frogs are highly similar to gastrulation and extraembryonic membrane formation in mammals
(4) late in organogenesis, at the phylotypic stage, the body plans of frogs and mammals are remarkably similar
4. The notochord is a ___ structure in vertebrate embryos that lies under the ___, and is flanked by ___.
(1) mesodermal, neural tube, somites
(2) endodermal, mesoderm, the gut
(3) ectodermal, neural tube, mesoderm
(4) mesodermal, ectoderm, endoderm
5. During gastrulation in Xenopus, the blastocoel
(1) becomes the gut
(2) is filled with endodermal cells and disappears
(3) is filled with mesoderm and disappears
(4) is displaced, and its original location becomes an endoderm lined cavity, the archenteron, which is a precursor to the gut
(Ans: 1-2; 2-2; 3-4; 4-1; 5-4)