A 'wrongful birth' case was recently brought before a court in wh...

Question

A 'wrongful birth' case was recently brought before a court in which a child with Smith–Lemli–Opitz syndrome was born to apparently healthy parents. This syndrome is characterized by a cluster of birth defects including cleft palate, and an array of problems with the reproductive and urinary organs. Originally considered by their physician as having a nongenetic basis, the parents decided to have another child, who was also born with Smith–Lemli–Opitz syndrome. In the role of a genetic counselor, instruct the court about what occurred, including the probability of the parents having two affected offspring, knowing that the disorder is inherited as a recessive trait.

What is the probability that one of them is a carrier and the other is not? [Hint: The p values in (b), (c), and (d) should equal 1.]

Accepted Answer

Hello everyone welcome back. Let's look at our next problem. It says in pea plants, the height of pea plants, seed color and seed shape are three independent events. The individual probabilities of the outcome of a cross between p plants that are hetero sickos for one particular trait are given as follows. The probability of the P plant being tall is 3/4 and that it is short is 1/4. Number two. The probability of the p plant having a round seed is 3/4 and having a wrinkled seed is 1/4 and number three. The probability of the p plant having a yellow seed is 3/4 and having a green seed is 1/4 two P plants that are hetero ziggy's for all three of the above traits are brought into the same cross calculate the probability of having a pea plant that is tall in height has a seat with a yellow color and wrinkled shape. And because it's a really big problem with lots of info, I'm just going to highlight the probability here that we're looking for. So we kind of focus in on our final answer here. So we know that we're looking for the outcome of a cross of plants. Hetero sickos for all three of these independent traits and we have the outcome of a cross of plants being hetero sickos. For each of the individual traits, we know they're independent. Um They're on so we can follow the law of independent assortment there on different chromosomes must mean. And if we wanted to draw punnett square. Um for cross involving three genes that makes a pretty big punnett square. So the simpler solution is to remember um our rule of combined probabilities. The product rule and the product rule says that the combined probabilities can be calculated by multiplying the individual probabilities. So we're given the individual probabilities. So let's find the combined probability. So the first event we have, we know that our p plant is tall in height. When we look at our individual probability, the probability of being tall Is 3/4. We're gonna multiply 3/4 times. Now we're gonna look at the next characteristic a seed with a yellow coat. Well, yellow seed is also 3/4. So multiply that by 3/4 And then our final characteristic, it says the seed should be wrinkled. When we look at the probability of having a wrinkled seed, that is 1/4. So we multiply by 1/4. So now again we're looking at the probability of having these three particular independent traits. Multiplying the three probabilities times each other. So three times three times one is nine in the numerator and four times four times four is 64. And the denominator. And our probability of our plant having all these three characteristics is choice B nine 64th. So again the probability of the P plant after a hetero sickos. Cross for plants Hetero sickos and all three traits. And looking at the probability of having a pea plant that is tall in height. Yellow seed and wrinkled seed is choice B9/64. See you in the next video.

Key Concepts

Recessive Inheritance

Carrier Probability

Punnett Square

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