As we have learned in this chapter, the Nanos protein inhibits the translation of hunchback mRNA, lowering the concentration of Hunchback protein at the posterior end of a fruit-fly embryo and stimulating the differentiation of posterior characteristics. The results of experiments have demonstrated that the action of Nanos on hunchback mRNA depends on the presence of an 11-base sequence that is located in the 3′ untranslated region (3′ UTR) of hunchback mRNA. This sequence has been termed the Nanos response element (NRE). There are two copies of NRE in the 3′ UTR of hunchback mRNA. If a copy of NRE is added to the 3′ UTR of another mRNA produced by a different gene, that mRNA is repressed by Nanos. The repression is greater if several NREs are added. On the basis of these observations, propose a mechanism for how Nanos inhibits Hunchback translation.
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
As we have learned in this chapter, the Nanos protein inhibits the
translation of hunchback mRNA, lowering the concentration of
Hunchback protein at the posterior end of a fruit-fly embryo and
stimulating the differentiation of posterior characteristics. The results of
experiments have demonstrated that the action of Nanos on hunchback
mRNA depends on the presence of an 11-base sequence that is located
in the 3′ untranslated region (3′ UTR) of hunchback mRNA. This
sequence has been termed the Nanos response element (NRE). There are
two copies of NRE in the 3′ UTR of hunchback mRNA. If a copy of
NRE is added to the 3′ UTR of another mRNA produced by a different
gene, that mRNA is repressed by Nanos. The repression is greater if
several NREs are added. On the basis of these observations, propose a
mechanism for how Nanos inhibits Hunchback translation.
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