Question

Predict the effect of the scenarios below on expression levels of each of these gene classes in the embryo described (will expression increase, decrease, or be unaffected) and explain the reason for your prediction.  

A) A fly embryo has a mutation that causes increased expression of the knirps gene (gap genes).  

B) A fly embryo has a mutation that blocks expression of the nanos gene (maternal genes).

C) A fly embryo has a mutation that decreases expression of the runt gene (pair rule genes).  

Answer 1

A) Gap gene is zygotic gene which is expressed when activated by product of maternal effect genes

Given here knirps gene is a gap gene so If their is mutation which cause increase of knirps gene than as we know gap gene determines broad region along anterior posterior axis and knirp gene determine a segment in anterior area of Embryo hence due to overexpression of knirp gene there will be an extra segment at anterior region which is expressed by knirps gene

B) Nanos gene is a maternal effect gene

Hence in Nanos deficient mutant their will be no abdomen formation in posterior region in embryo

C) Runt gene is a primary Pair rule gene which is zygotic expression gene

Hence hence if their is mutation that decrease expression of runt gene than their will be absence of every other segment in embryo

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