Billy and Johnny are brothers,but they do not look alike. Which one of the following pairs variation? crowing over and independent assortment menul reproduction and the cell cycle enchiness and cloning

## Step 1<br />The problem is asking us to identify the pair of terms that best explains why Billy and Johnny, who are brothers, do not look alike. This is a question about genetics, specifically about the mechanisms that can lead to variation among siblings.<br /><br />## Step 2<br />The first pair of terms, "independent assortment" and "crossover", are both mechanisms that can lead to genetic variation. Independent assortment refers to the random distribution of chromosomes during meiosis, which can result in different combinations of traits. Crossover, on the other hand, is the process where homologous chromosomes exchange genetic material during meiosis, leading to new combinations of genes.<br /><br />## Step 3<br />The second pair of terms, "mitosis" and "the cell cycle", are not directly related to genetic variation. Mitosis is a process of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. The cell cycle is the series of events that take place in a cell leading to its division and duplication.<br /><br />## Step 4<br />The third pair of terms, "meiosis" and "cloning", are also not directly related to genetic variation. Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. Cloning is the process of creating an exact copy of a biological entity.<br /><br />## Step 5<br />Based on the above analysis, the pair of terms that best explains why Billy and Johnny do not look alike is "independent assortment" and "crossover".