Question

What is the shortcut to finding the probability of having a certain outcome in biology genetics. It is supposedly solvable using a Prunett square which is a square showing all the possibilities but when you get to 16 total possibilities, I can't possibly draw a 16 answer box for every question. Others did this with 2 boxes of 4 each, but I can't figure out why. Help!

The concrete example question is: Mother is YYRR and Father is yyrr. What are the chances of an offspring having a YRyr combination.

Answer 1

Nice question.. a bit tricky too

Answer 2

They say that this is the same as rolling dice. Again, not seeing how..... :(

Answer 3

a concrete example is: Mother is YYRR and Father is yyrr. What are the chances of an offspring having a YRyr combination.

Answer 4

so there possible value are
Y ,y
R,r
?

Answer 5

first one

you have 4 choice

then 3 , so on

4*3*2*1=24

Answer 6

I understand how to find the total possible combinations but not the chance of getting a specific one. Also in YYRR and yyrr, the possibilities can be Yyrr, or YYrr, etc etc, but what are the chances of getting a an offspring that would have any order of capital Y and small r....
More specifically , a square would show all combos but i only filled in some below. I know there is a shorter way than writing this out and literally counting the number of times a specific one would show up for every question. I just can't figure out how. :( I hope I'm being remotely clear in the way I'm wording this....

YY RR YR RY

yy YYyy RRyy YRyy RYyy

rr

yr

r y

Answer 7

if they have uniform chance, it would be 1/24

Answer 8

how did you get that number?

Answer 9

see above

Answer 10

I'm sorry, I do see that, thank you but what I mean is, I thought there were only 16 possibilities?

Answer 11

how did you see 16 possiblity

Answer 12

from the possibility square I drew, the prof drew that in class

Answer 13

The simpler version is mom has 2 genes for B, blue eyes (BB) and dad has 2 genes for brown (b) eyes. What are the chances of having an offspring with the Bb combination.

mom

B B
Dad b Bb Bb

b Bb Bb

The chance is 100%, BUT, if mom has Bb and dad has bb, what are the chances of having bB offspring

mom B b

dad b Bb bb
b Bb bb
The this probability is 50%

In the other question, the number of genes is doubled. Does this help?

Answer 14

if mom is Bb and dad is bb
we could have

only two possibility

first letter could either be B or b =2
second letter could just be b =1

2*1=2
2 choices

1/possible choices= probability
1/2=50%
so 50%

previous example

BB and bb

first letter could be B =1
seond letter could be b=1
1*1=1
so 100%

Answer 15

clear?