The last time you saw the sisters pictured above, you considered how different protein molecules in their cells could lead to different traits. Now, you know that genes provide instructions for proteins that lead to traits. How could these sisters have ended up with different genes, leading to their different proteins and traits? Explain your ideas below.​

recombination and independent segregation of chromosomes during meiosis  

Explanation:

Recombination and independent segregation of chromosomes represent the two most important meiotic mechanisms by which sisters from the same parents can inherit different gene variants and therefore look very different from each other:  

1- Independent assortment (segregation) of chromosomes: during meiosis, homologous chromosomes are randomly distributed in daughter cells (which will give rise to the gametes), and therefore separate independently of each other. It is for that reason that gametes have unique combinations of chromosomes, which increases genetic variation.

2- Recombination, also known as crossing over, refers to the exchange of chromosome segments between non-sister chromatids during meiosis. This mechanism is well-known to produce new gene variants (alleles) in the daughter cells. In consequence, recombination also increases the genetic variation of the resulting gametes that will produce offspring (in this case, different sisters).