Genotypes in diploid/haploid cells under mitotic/meotic cell divisions
Though broad, here I provide a summary in graphical way.

Mitosis:

 .



MEIOSIS: 2 successive steps : Meiosis-1 and meiosis-2

Meiosis-1





Meiosis-2





So lets see what happens with cells given at question.

1. Cell with genotype Aa

(monohybrid or one-point cross-experiments; that means we are looking to gene-pair at 1 loci; not looking to any other genes): 

1. A.  Mitosis:

Possible genotypes of their offsprings: All Aa. 

1. B. Meiosis: 

gametes will show 2-possibilities ; A, a.



2. Cell with genotype AaBb 

(dihybrid or 2-point cross-experiments; that means we are looking on genes of 2 loci; not to any other cells): 

2.A. Mitosis:

all offsprings AaBb. 

2.B. Meiosis: 

If given condition says the loci for A (or a) and B (or b) are on same chromosome (linked genes) and no crossing-over is there;

then We will get only 2 types of gamete AB and ab. 

If crossing over(s) take place between the 2 loci; then we'll get 4 types of gamete AB, Ab, aB, ab; but their ocurring frequency will deviate from Mendel's independent assortment. 

If the 2 loci are not-linked; i.e. they are located in distinct chromosome; then also we'll get 4 types of gametes AB, Ab, aB, ab; but they will follow Mendel's independent assortment pattern.


  Reference:
  
  
  Concepts of Genetics, 8th Edition (EBook) By William Klug, Michael Cummings, Charlotte Spencer / Pearson; chapter 2 (mitosis and meiosis)
  The science of Genetics, 6th edition, by George Burns and Paul Bottino, Macmillan.
  Genetics/ P.K. Gupta/ Rastogi Publication Meerut