Welcome Guest Search | Active Topics |

Tag as favorite
Genetic Probabilities
Options
Previous Topic Next Topic
Natasha_4902
#1 Posted : Friday, July 03, 2020 6:10:39 PM
Rank: Advanced Member

Groups: Registered
Joined: 6/8/2020
Posts: 62

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi,

For questions asking about the probability/chance of certain conditions happening that are more complex than a punnet square could solve, how do you determine what number is the base and what number is the exponent?

For example, which expression gives the probability that a mother and father will have 4 children, 2 girls and 2 boys, in any birth order?

Is there a certain pattern we can use to solve these questions?

Thank you
Back to top
Report?
INSTR_Katerina_102
#2 Posted : Sunday, July 05, 2020 5:48:22 PM
Rank: Advanced Member

Groups: Registered
Joined: 6/24/2019
Posts: 250

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi,

Usually when I address these questions I try to use this kind of approach.

P = (# ways to desired result)/(Total # of ways)

Usually for this type of question total number of ways is convenient to access.

Here we have 4 children with 2 options of sex.

2*2*2*2 = 2^4 = 16 possible ways.


Therefore our P = (# of ways to 2B2G)/(Total # of ways)

For a larger dataset you might need more advanced math, but for this type of question and MCAT questions the math is generally simpler.

We can use the BBGG and count the number of ways to get this:

BBGG
GGBB
BGGB
GBBG
BGBG
GBGB

Getting a total of 6 ways to 2B2G.

This simplfies our P = 6/16 = 3/8 = 37.5 %

I think there are more elegant mathematical ways to do this, but I don't know them off the top of my head, nor do I know any particular patterns to this type of question.

I often find it more comforting on the MCAT to have written down some of my reasoning on scrap as if I have it as an abstract formula it's harder to check/recall when you are checking over questions.
Back to top
Report?
Users browsing this topic
Guest (2)
Tag as favorite
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Clean Slate theme by Jaben Cargman (Tiny Gecko)
Powered by YAF | YAF © 2003-2009, Yet Another Forum.NET
This page was generated in 0.070 seconds.