Karen and Steve each have a sibling with sickle-cell disease (recessive disorder). Neither Karen nor Steve nor any of their parents have the disease, and none of them have been tested to reveal sickle-cell trait. Based on this incomplete information, calculate the probability that if this couple has a child, the child will have sickle-cell disease.

To first understand your question, here are some vocabulary terms I will be using throughout this problem.

We know that having sickle cell disease is a recessive disorder so it will be homozygous recessive (bb).

We also know that Karen and Steve each have a sibling with sickle cell disease, but they don't. This means that both of their parents have to be heterozygous (Bb), or a carrier for the disease.

If their parents are both heterozygous (Bb), there is a 1/4 chance that Karen and Steve are completely healthy (BB) and a 2/4 chance that they are carriers (Bb). We know for a fact that they aren't sick so that is out of the question.

This means that the probability of Karen and Steve being a carrier for this disease is 2/3.

Now, we can make a Punnett square for the probability of their children, which I have attached below. Since being heterozygous is most likely, I made both Karen and Steve heterozygous in the Punnett square.

This means that their children are 1/4 likely to be completely healthy (BB), 2/4 likely to be a carrier (Bb), and 1/4 likely to have sickle cell disease (bb).

Now we can multiply the probability of both of Karen and Steve being a carrier for sickle cell, which is 2/3 each, with the probability of their children having it, which is 1/4.

2/3 × 2/3 = 4/9

4/9 × 1/4 = 1/9

The final probability of Karen and Steve having a child with sickle cell disease is 1/9.

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion

human-caused climate hope this