Chapter 1 Flashcards
Who is Gregor Mendel and what he discovered?
Gregor Mendel is the “father of modern genetics”, who discovered the principles of inheritance through his work on pea plants
What are the 7 antagonistic pairs of traits in peas that Mendel studied?
What is the Monohybrid cross?
It’s a one factor cross between parents that differ in only one trait, which is controlled by only one gene.
What Mendel revealed through the monohybrid cross?
Mendel revealed the units of inheritance (2 per individual) and the law of segregation
What is the Dihybrid cross?
It’s a two factor cross between parents that differ in 2 observed traits that are controlled by two distinct genes (color: green/yellow and shape: round/wrinkled)
What Mendel revealed through the dihybrid cross?
Revealed the law of independent assortment
What are the 4 Mendel’s postulates?
- Unit factors in pairs
- Principle of Dominance / Recessiveness
- Law of Segregation
- Law of Independent Assortment
What means “unit factors in pairs” postulate?
A unit factor is the trait (tall gene or dwarf gene), which inherits one allele from the mother and the other allele from the father (2 alleles together one gene)
What is the Principle of Dominance / Recessiveness?
In the pair of unit factors (alleles) for a single trait (phenotype) in a single individual, one unit factor (allele) is dominant to the other allele, which is recessive.
What is the Law of Segregation?
The two alleles for each trait separate (segregate) during gamete formation.
One gamete from each parent (total 2 gametes) unite at random at fertilization. For example, there is an equal probability that each gamete will receive either the tall unit factor or the dwarf unit factor.
What is the Law of Independent Assortment?
The law that states that each allele segregates into gametes independently of all other alleles in meiosis during gamete formation (producing genes)
- Y is just as likely to assort with R as it is with r
- y is just as likely to assort with R as it is with r
In the Monohybrid cross, each F1 hybrid produces 2 kinds of gametes in a 1:1 ratio. What are the expected genotype/phenotype ratios for the F2 progeny?
1: 2:1 ratio of genotypes and
3: 1 ratio of phenotypes
In the Dihyrbid cross, each F1 hybrid produces 4 kinds of
gametes in a 1:1:1:1 ratio. What is the expected phenotype ratio for the F2?
9:3:3:1 ratio of phenotypes
What is the Trihybrid cross?
It is the cross between the two individuals, which have 3 different genes that produce 3 or more traits corresponding to each gene. A gene (genotype) will determine a trait (phenotype)
What is the Fork Line Method/ Branch Diagram?
It’s the method, which breaks down multihybrid crosses into independent assorting monohybrid crosses that determine the
likelihood of each possible phenotype.
What is the probability of an event?
The probability of an event is the chance that the event will occur in the future.
• Probability = Number of times an event occurs/ Total number of events
For example, in a coin flip, P heads = 1 heads/ ( 1 head + 1 tail)= ½ or 50%
What is the Product Law?
Probability of two independent events occurring at the same time is equal to the product of their individual probabilities. With independent events:
Probability of event 1 AND event 2 = Probability of event 1 * probability of event 2.
Example: From a cross of Yy and Yy peas, what is the chance of getting YY?
Chance of Y pollen is ½ from Yy (male) and chance of Y ovule is ½ from Yy (female), so the chance of getting YY is (1/2) X (1/2) = ¼
What is the Sum Law?
Sum Law is used to calculate the probability of a generalized outcome that can be
accomplished in more than one way.
The probability of event 1 OR event 2 = Probability of
event 1 + probability of event 2
For example: What is the chance of getting Yy offspring from a
cross between Yy and Yy peas?
Chance of Y ovule uniting with y pollen (1/2) x (1/2) = ¼
Chance of y ovule uniting with Y pollen (1/2) X (1/2) = ¼
Chance of either event?? happening = (1/4) + (1/4) = ½
What Binomial Expansion Equation represents?
Represents all of the possibilities for a given set of unordered events
n= # of events
x=number of events in 1 category
p=individual probability of x
q= individual probability of other category
What is factorial?
It’s the product of an integer and all the integers below it.
p + q = 1 and the symbol ! denotes a factorial
n! is the product of all integers from n down to 1
4! = 4 X 3 X 2 X 1 = 24, An exception is 0! = 1
What relationship does sample size and deviation have?
As sample size increases the average deviation
from the expected results decreases.
This means that we get closer to our predicted results,
when we have a higher number of observations.
• Ex. Tossing a coin 1000 times vs 10 times
Sample size meaning?
Sample size refers to the number of observations included in a study.
What is the Null Hypothesis?
Assumes that there is no real difference between the measured values and the predicted values, and that difference is purely to chance.
What is the simplest statistical test to assess the Null Hypothesis?
Simplest statistical test to assess is the Chi-Square analysis
What is The Chi Square Test?
A statistical method used to determine goodness of fit
– how close the observed data is to those predicted from a hypothesis
2. The chi square test does not prove that a hypothesis is correct
It evaluates whether or not the data and the hypothesis have a good fit
What is the degrees of freedom?
Degrees of freedom (df) = n-1,
where n is the # of different categories into which each point may fall.
– For the 3:1 ratio n=2, so df= 1
– For the 9:3:3:1 ratio n=4, df=3
Why take degrees of freedom into account?
The greater # of categories, the more deviation expected due to chance
When do we accept our Null Hypothesis?
If p > 0.05, accept that chance is responsible for the deviation
between the observed and expected. (Accept our null hypothesis)
– p = 0.6 means that there is a 60% probability that any
deviation from expected is due to chance only. This is within
the range of acceptable deviation.
– Accept null- any deviation is due to chance
When do we reject our Null Hypothesis?
If p < 0.05, conclude that some factor other than
chance is operating for the deviation to be so great.
– a p value of 0.01 means that there is only a 1% chance that
this deviation is due to chance alone. Therefore,
other factors must be involved.
– Reject null - observed deviation is not attributed to chance
What is Pedigree?
A pedigree shows a family tree with respect to a given trait.
