Question

1. What is the difference between a parasegment and segment in Drosophila development?

a) Segments correspond to the anatomical divisions seen in larvae and adults, whereas parasegments are subdivisions of the embryo that correspond to regions or domains of gene expression.

b) Parasegments correspond to the anatomical divisions seen in larvae and adults, whereas segments are subdivisions of the embryo that correspond to regions or domains of gene expression.

2. Which of the following statements about vertebrate Hox genes is true?

a) Vertebrate Hox genes are examples of housekeeping genes that are constitutively expressed.

b) Vertebrate Hox genes lack the homeobox DNA sequence found in most invertebrate homeotic genes.

c) Hox genes are expressed in an anterior-to-posterior pattern that corresponds to the chromosomal position of the genes within the Hox cluster.

d) Vertebrate Hox genes are dispersed throughout the genome. They are not arranged in clusters as in invertebrates.

3. What is the mechanism by which the nanos protein regulates early embryogenesis in Drosophila?

a) It stimulates translation of hunchback mRNA.

b) It stimulates transcription of the hunchback gene.

c) It represses transcription of the hunchback gene.

d) It represses translation of hunchback mRNA.

4. What is the pattern of bicoid mRNA distribution in the early Drosophila embryo?

a)restricted to the posterior pole region of the embryo

b) restricted to the anterior pole region of the embryo

c) uniformly distributed along the anterior-posterior axis of the embryo

d) in a gradient with the highest concentration in the anterior, decreasing to none in the posterior quarter of the embryo

Answer 1

1.a

2.c

3.d.

4.b.

Explanation

1.a. segments correspond to the anatomical divisions seen in larvae and adults, whereas parasegments are subdivisions of the embryo that correspond to regions or domains of gene expression.

Explanation:

2.c. Hox genes are expressed in an anterior-to-posterior pattern that corresponds to the chromosomal position of the genes within the Hox cluster.

Explanation : In many animals, the organization of the Hox genes in the chromosome is the same as the order of their expression along the anterior-posterior axis of the developing animal, and are thus said to display colinearity.

3.d.  It represses translation of hunchback mRNA

Explanation: The Drosophila Nanos protein is a localized repressor of Hunchback mRNA translation in the early embryo, and is required for the establishment of the anterior-posterior body axis.

4.b. restricted to the anterior pole region of the embryo.

Explanation: The initial steps in specification of the antero-posterior
axis of the Drosophila embryo are regulated by graded
signals emanating from each pole of the egg.
These graded signals, #(Bicoid (Bed) protein at the anterior )
and Nos protein at the posterior, are generated by trans-
lation of localized mRNA precursors. . So, Bicoid mRNA is restricted to anterior pole region of the embryo.

Or

In other words, The anterior region of the Drosophila embryonic pattern is determined by a gradient of the bicoid (bcd) protein. The correct formation of this gradient requires the localization of bcd RNA to the anterior pole of the egg.