## creighton 3 years ago Can some explain what how to solve for the fourth generation of a pedigree.

1. wach

A fourth generation .. That should be your grandparents, then. I can help you, to an extent. Just describe more on what you're supposed to do, please.

2. wach

Did they give you the first 3 or last 3 generations?

3. wach

Usually, a 4-generation chat goes like this: 1st: You, and siblings 2nd: Your parents 3rd: Your grandparents 4th: Great-grandparents and etc.

4. wach

Well, if you can find the parents of whoever is in the 3rd generation, you should be able to find your answer. If not, there are certain clues you can deduct from. Like for example, generally the last name(s) of the male(s) in the 3rd generation have the same last name as their parents.

5. creighton

hold on I going to attach a pic

6. creighton

7. wach

Sorry, I don't really understand. I wish you good luck, though :)

8. creighton

This is the question I am trying to figure out how to do. The pedigree chart below shows the individuals in a family who exhibit in a family who exhibit a certain trait. Based on the information in the chart, what are the chances that a second child born to couple 4-5 in the third generation will show the trait Choices 25% 50% 100% 0%

9. creighton

I know that it is not 50%

10. creighton

Or 0%

11. wach

Oh, I see. So, if the 1st child born to the couple expressed the trait (as shown in yellow) but the parents both didn't, we know that it must be a recessive trait, right? If this trait is represented in terms of T/t, with the small t being the recessive one that gives the trait, that must mean that the parents are both Tt. Does that sort of make sense?

12. creighton

kind of

13. wach

That means a chart for their possible children would be like this: |dw:1344888602483:dw|

14. creighton

I understand the chart but how does this help?

15. wach

Okay. Let's think about the couple, 4 and 5. Assume that circle = female, and square = male. 4's mom displayed the recessive trait, so that means that she was tt. Two of 4's siblings displayed the trait, and two didn't. However, because 4's mom had tt, we can assume that 4 has one t in their genetic coding, and that they're Tt because they didn't display the trait, meaning they got one dominate allele.

16. wach

The same reasoning goes for 5's dad, who had tt because they displayed the trait. But 5 themself didn't display the trait, meaning they're Tt. Does that sort of make sense?

17. creighton

yes

18. wach

So, the table that I drew shows the possible outcomes for 4 and 5's kids. There is a 75% chance that the kid won't display the trait (TT, Tt, and Tt are dominate) There is a 35% chance the kid will display the trait (tt) Does that answer your question? :)

19. creighton

Yes, thank you so much :)

20. bbbco123

so it would ebe 0?