Question

Which one of the following statements is totally wrong about the occurrence of notochord, while the other three are correct?
A. It is present only in larval tail in ascidian
B. It is replaced by a vertebral column in adult frog
C. It is absent throughout life in humans from the very beginning
D. It is present throughout life in Amphioxus

Answer 1

Hint: Notochord is present in the foetal life of humans. And the vertebral column in the adult front has been replaced by the larval stage of the frog. Ascidians are a part of the tunicates family that belong to the phylum Chordata and have contained notochord present in their larval stage and slowly replaced by a single elongated solid nerve ganglion that’s known as cerebral ganglion.

Complete answer:
The Notochord is present in the large part of the regulator embryonic patterning in vertebrates. Abnormal notochords lead to birth defects in the human body and these birth defects can be understood by the study of pathogenesis. In pathogenesis not only human data is present that is obtained by the notochord study but as well the data obtained by the animal’s defects from the birth are also available on that.
The Notochord is present in the neural tube in vertebrate embryos and showing rod like structure. If any birth defects arise in the body, notochord helps to maintain the left right asymmetry. And also play a very important role in the adjunct tissues in early vertebrate development.
Humans, vertebrates and cephalochordates group of animals have evolutionary well preserved structure and are named after the Notochord.

Therefore the correct option is (c).

Note: In the vertebrae, neural tube, and cranial region the abnormal development result of the malformations of the gut. There are three human families in which the notochord canal is present due to the mutation in the brachyury gene which encodes the gene in the pathway of the axial mesoderm differentiation.