72. In an organism, expression of gene ‘X’ is induced in the presence of a hormone genetic analysis showed that the hormonal signal is transduced through two proteins Let1 and Let(2) The expression of gene ‘X’ was studied
    in lines over expressing (OE) the active Let proteins knock out (KO) of the Let proteins or combination of both. Results of expression of gene ‘X’ in presence Of the hormone is
    summarized below:Based on the above, which one of the

following pathways best fits the observation
made?

Hormone-Induced Gene Expression via Let1 and Let2: Interpreting Genetic and Signaling Pathways

Introduction

The expression of gene ‘X’ is induced by a hormone whose signal is transduced by two proteins, Let1 and Let2. Genetic analysis involving overexpression (OE) and knockout (KO) of Let1 and Let2 provides clues about the signaling pathway regulating gene ‘X’. Understanding such pathways is key to dissecting hormone-mediated gene regulation.

Signaling Pathways Overview

• If Let1 and Let2 function in series (linear pathway): One protein activates the other in sequence. Expression changes with OE or KO of either protein, reflecting dependency.

• If Let1 and Let2 function in parallel (independent branches): Each can independently influence gene ‘X’. KO of one may reduce expression but not abolish it; OE effects may be additive.

• If Let1 negatively regulates Let2 or vice versa: Complex expression patterns may emerge.

Interpreting Experimental Observations

Given:

• OE of Let proteins increases gene ‘X’ expression.

• KO reduces or abolishes gene ‘X’ expression.

• Combination of OE and KO may help deduce order and relationships.

Depending on the summarized results (not detailed here), the best model may involve:

• Sequential activation: Let1 ➔ Let2 ➔ gene ‘X’ induction

• Parallel pathways: Let1 ➔ gene ‘X’; Let2 ➔ gene ‘X’

Technical genomic and protein interaction data (from sources like , ) often support combined regulatory modules with cross-talk.​

Biological Significance

Hormone signaling often involves integration of multiple proteins to finely tune gene expression. Let1 and Let2 may be transcription factors, kinases, or scaffolding proteins enabling signal propagation, consistent with examples in hormone responses outlined in recent studies on transcription factor dynamics and hormone receptor pathways.

Summary

While exact pathway details depend on data, a plausible model is: Hormone activates Let1, which activates Let2, together inducing gene ‘X’. This fits common hormone signaling architectures where multiple proteins act in sequence or in regulatory complexes.