def recherche(gene, seq_adn):
    n = len(seq_adn)
    g = len(gene)
    i = ...
    trouve = False
    while i < ... and trouve == ... :
        j = 0
        while j < g and gene[j] == seq_adn[i+j]:
            ...
        if j == g:
            trouve = True
        ...
    return trouve