DropDownList Cascade and MVC Compound

I have a following doubt

I have 1 User class and it consists of other classes Gender, Course and Semester

Ex

    public int Id { get; set; }
    public string Nome { get; set; }
    public Genero Sexo { get; set; } = new Genero();
    public Curso Curso { get; set; } = new Curso();
    public Semestre Semestre { get; set; } = new Semestre();

And my question is in my controller to popular my DropDownListFor

My DAO Courses Equal to Course and Semester

    public List<Genero> ListarGenero()
    {
        var Genero = new List<Genero>();
        SqlDataReader reader;

        using (contexto = new Contexto())
        {
            var strQuery = " SELECT * FROM Genero ";
            reader = contexto.ExecutaComandoComRetorno(strQuery);

            while (reader.Read())
            {
                var temObjeto = new Genero()
                {
                    id = int.Parse(reader["Id"].ToString()),
                    Sexo = reader["Genero"].ToString()
                };
                Genero.Add(temObjeto);
            }
        }
        reader.Close();
        return Genero;
    }

My Action

    public ActionResult GetGenero()
    {
        GeneroDAO gen = new GeneroDAO();
        ViewBag.Genero = new SelectList(gen.ListGenero(), "Id", "Sexo");
        return View();
    }

View

     @Html.DropDownListFor(model => model.Sexo.id, (SelectList)ViewBag.Genero, new { @class = "form-control" })

I searched on some forums and found nothing using composition I would like to make dropdowns popular from the bank and also cascade in the course, I just found JavaScript but I can not use it because it does not recognize the composition of the other classes.