Lecture 4: Mendelian Genetics

Question 1

Probability

Answer 1

Likelihood of the occurrence if a particular event

• 0 = not gonna happen
• 1 absolutely gonna happen

Question 2

Multiplication rule

Answer 2

Multiply the probability o independent events happening simultaneously

• what is the probability of rolling a 4 twice in a row?
  = 1/6 x 1/6 = 1/36

Question 3

Addition rule

Answer 3

When two events are mutually exclusive the probability that EITHER A or B will occur

What is the probability of rolling EITHER a 3 or a 4 on a given rolll?
- 1/6 + 1/6 = 2/6

Question 4

Phenotype and ration

Answer 4

The physical appearance of the gene (blue hair, green eyes…)

• Aa x Aa parents = 3:1
• Aa x aa parents = 1:1

Question 5

Genotypic and ratios

Answer 5

The genes involved that create the trait

• Aa x Aa parent = 1:2:1
• Aa x aa or AA x AA parent = 1:1

Question 6

Conditional probability

Answer 6

Probability of an event A, given that event B has already occurred

Question 7

What is the formula for two variables an what are they

Answer 7

(P+q)^n

P = frequency of an outcome
Q = frequency of another outcome
N = number of events
P+Q = 1

Question 8

Dihybrid cross

Answer 8

Involve 2 traits weigh differing alleles

• by observing the two traits Mendel was able to reveal the principle of independence assortment

Question 9

Independent assortment

Answer 9

Results from the independent separation of chromosomes in anaphase 1

Question 10

Chi squared goodness of fit

Answer 10

Test that indicated the probability that the difference between the observed and expected values are due to chance

Question 11

What are the three assumptions with the chi squared test

Answer 11

Random sample - the sample data is a random sample of a larger population

Sample size - is sufficiently large to prevent small sample error

Independence - the observations are independent of each other

Question 12

Degrees of Freedom

Answer 12

Number of values that are free to vary minus 1

= 2 characters
- 2-1 = 1

So 1 is the degrees of freedom

Question 13

Why us a chi squared test

Answer 13

Used to determine that the diff between observed and expected values is due to chance

Question 14

Multiple testing problems and solution

Answer 14

Multiple comparisons arise when a stat analysis involves multiple stimultaneous stats test

For example, if we test the impact of a drug and weigh them in 20 different responses like blood pressure, heart rate temperature, nausea, etc. the chance finding a false positive high because all the variables being tested

We need to calculate the probabilities obtained from a stat, which was repeated multiple times