Chapter 12.1.4 (Exam 3) Probability Flashcards
Inheritance of Genes Follows Mendelian Laws
Mendel also tested inheritance patterns involving two different genes. How did he do so?
Test: Cross true-breeding peas differing in two characteristics, seed shape and color (a dihybrid cross)
Round, yellow seeds (RRYY)
Wrinkled, green seeds (rryy)
F1 generation is RrYy—all round yellow
What did Mendel do with the resultant F1 generation of his dihybrid cross?
He crossed the F1 generation (double heterozygotes)
Mendel asked whether, in the gametes produced by RrYy, the traits would be linked or segregate independently. What did he find?
The traits were independently segregated, F2 had 9 different genotypes; phenotypes were in a 9:3:3:1 ratio
What is Mendel’s second law?
Independent assortment: Copies of different genes assort independently
Chromosomes segregate independently during formation of gametes, and so do any two genes located on separate chromosome pairs
What was one of Mendel’s keys to success?
One key to Mendel’s success was large sample sizes
Using probability calculations and statistical techniques
What is the probability of an event that is certain to happen? To not happen?
1
0
What is the probability of events that are uncertain to occur?
Between 0 and 1
What is the multiplication rule?
Probability of two independent events happening together : multiply the probabilities of the individual events
For example, tossing two coins: probability that both will come up heads = 0.5 * 0.5 = 0.25
Explain how the multiplication rule can be applied to a monohybrid cross.
F1 Rr plant self-pollinates; probability that gamete will have either gene is 0.5.
Probabilities of F2 genotypes:
RR = 0.5 * 0.5 = 0.25
rr= 0.5 * 0.5 = 0.25
What is the addition rule?
The probability of an event that can occur in two different ways is the sum of the individual probabilities
In F2, there are two ways to get Rr:
0.25 + 0.25 = 0.5
