Most of the names of jobs or occupations in Russian have ONLY one form - masculine. That is the general rule. The examples are numerous: доктор (a doctor), врач (another word for "a doctor"), адвокат (a lawyer), судья (a judge), солдат (a soldier), прокурор (a prosecutor), биолог (a biologist), учёный (a scientist), пилот (a pilot), водитель (a driver). All these words are applied to both male and female professionals. The gender is strictly grammatical - it belongs to a word, and NOT to a person performing his or her job. Михаил врач. Он хорошИЙ врач. Елена тоже врач. Она тоже очень хорошИЙ врач.
Some of the occupations in Russian change by gender - they have two different forms according to the gender of the person who is performing the duties. STILL, you can always use the masculine form while talking about a man or a woman (MALE gender always prevails in Russian). It is totally up to you whether to use the feminine word for a female worker, or the male word. BUT NOT vice versa. And this is exactly WHY you can apply the word ПОЭТ to describe a female poet in Russian. Михаил - учитель. Елена тоже учитель. OR: Елена тоже учительница. The examples of such male/female pairs are: учитель/учительница (a teacher), журналист/журналистка (a journalist), спортсмен/спортсменка (a sportsman/a sportswoman), директор/директрисса (a director), продавец/продавщица (a sales assistant), официант/официантка (a waiter/a waitress), поэт/поэтесса (a poet), писатель/писательница (a writer).
Very few jobs are strictly feminine in Russian. They formed as a result of long history when only women were performing those duties. The examples are: балерина (a ballerina), няня (a nanny).
In some cases, the names of jobs that only exist in a masculine gender can be transformed into a female gender using the word-formating means of the Russian language, but most of the time they will become offensive. Some examples are: врачиха (a female doctor), биологичка (a female teacher of biology).