Question

You have identified a recessive mutation in the mouse, in which expression of the mouse dickkopf gene is strongly disrupted (i.e., expression is reduced to 5% of normal levels). Individuals homozygous for this mutation

	A.	fail to form heads
	B.	fail to gastrulate
	C.	fail to induce neural tissue
	D.	form giant heads

Answer 1

Dickkopf genes in mouse have been found to be involved in the embryonic head induction and limb morphogenesis. As provided in the question, we have identified a recessive mutation in the mouse where the expression of this gen has been strongly disrupted. therefore the individuals homozygous for this mutation would not be able to produce the required levels of the protein and it will definitely produce embryos lacking head structures. hence option A appears most appropriate.

Rest of the options donot have any chance as it has liitle no effect on gastrulation, or induction of neural tissue. the formation of gaint heads is not possible at all.

Thank u

Scientists have created a DKK1 knockout model in mice that revealed the effects of this gene. All mice that were homozygous for the DKK1 knockout were dead at birth due to defects in the cranium and structures formed by the neural crest, such as failed development of eyes, olfactory placodes, frontonasal mass and mandibular processes, as well as incomplete development of the forebrain and midbrain and fusion of the digits of the forelimb.[7] This evidence supports the idea that inhibition of the Wnt signaling pathway by DKK1 is crucial to proper cranial development.