Which model most accurately describes how Hox genes regulate embryonic developme
ID: 225724 • Letter: W
Question
Which model most accurately describes how Hox genes regulate embryonic development in Drosophila?
Which model most accurately describes how Hox genes regulate embryonic development in Drosophila?
A. Hox gene expression does not overlap among segments or parasegments. The product of each gene is confined to its own domain along the anterior-posterior axis to specify identity. B. Hox gene expression is necessary for segment formation.The absence of Hox gene expression leads to a lack of segment formation. C. Hox gene expression corresponds to segmental boundaries. It is the unique combination of Hox gene products that mark the boundaries of each segment. D. Hox gene expression marks the boundaries of parasegments. Each parasegment expresses a unique combination of Hox gene products that give rise to the identity of each parasegment.Explanation / Answer
Correct answer D
Background:
Homeobox-containing (or HOX) genes are present in found in many life forms including insects, birds, mammals, and even plants.
These are found in clusters, and the intra-cluster gene order is usually conserved between different species for example an insect and a mammal.
Even the sequence and timing of expression of these genes within the chromosome matches their site of expression along the anterior/posterior axis, for example hox genes related to head would be followed by that of thorax and then by that of abdomen (just like the body plan).
hox genes encode transcription factors which are instrumental in regulating body formation during development.
Segments in Drosophilia are formed from the posterior of one parasegment and the anterior of the next parasegment. In total there are 14 parasegments three forming mouth, three forming thorax, and eight forming abdominal region.
The Drosophila genome has eight hox genes clustered in two complexes.
Analysis of options
A. False, because to make 14 parasegments from 8 hox genes you need some overlap of expression.
B. False, absence would lead to a misplaced segment.
C. False, as segments are formed from parasegments and hox genes mark the boundary of a parasegment.
D. True, just based on above reasoning
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