Lec 4. Basic principles of Heredity Flashcards
Who is Mendel?
Set out mathematically description how some genes are passed down from one generation to the next.
What was the model organism Mendel used?
Pea plant
What does homozygous mean?
True breeding. The alleles are identical
Define a Monohybrid cross
Cross between two parents that differ in a single characteristic
What four conclusion can be made from the Monohybrid cross?
Each characteristic is encoded by two genetic factors, these two characteristics somehow separate during reproduction, the concept of dominant and recessive traits, two alleles separate with equal probability into the gametes.
What is Mendel’s first law?
Principle of segregation
Define principle of segregation
For every characteristic we have a pair of genes and they segregate INDEPENDENT from on another and only one is passed from each parent.
What is independent assortment?
Alleles segregate independently when gametes are formed.
Define the concept of dominance
When two different alleles are present in a genotype, only the trait encoded by one of them-the dominant allele- is observed in the phenotype. The other is called recessive.
How do monohybrid crosses explain the principle of segregation?
Capital=dominant. Lower case= recessive trait. The symbols in the crosses correspond to alleles on chromosomes.
What is the Chromosomal Theory of Heredity (1902)?
identified chromosomes as the genetic material responsible for Mendelian inheritance. (sutton)
How is cystic fibrosis caused?
Mutations in the CFTR gene. Mutations are usually recessive
Define probablility
likelihood of the occurrence of an event
What is probability used for in genetics?
predict the outcome of a genetic cross
How is probability quantified as a number?
Between 0 and 1. 0 is impossible. 1 is certain.
What are probabilities numerically described as?
As the number of desired outcomes divided by the total number of all outcomes
What is the multiplication rule?
Multiply the probability of independent events happening simultaneously.
What is the addition rule?
When two events are mutually exclusive, the probability that either A OR B will occur is the sum of the probability of each event. Big word here is OR.
What is conditional probability?
probability of an event A, given that another B has already occurred.
What is the binomial equation used for?
Used to calc simple and complicated crosses with multiple genes
What is the binomial equation?
(p+q)^n
What do the variables in the binomial equation stand for?
p= frequency of one outcome. q= frequency of the other outcome. n= number of events. Know that p+q equal 1.
What is a Dihybrid Cross?
a cross that deals with 2 traits, with differing alleles.
How did Mendel reveal the principle of independent assortment?
By examining the behavior two traits simultaneously. Dihybrid cross.
Where does the principle of independent assortment result from?
From the independent separation of chromosomes in Anaphase I of meiosis.
What is a branch diagram and what can it be used to determine?
Another way to show a punit square, determines the phenotypes and expected proportions of offspring from a dihybrid cross.
What do Dihybrid crosses show?
Relate the principle of independent assortment to meiosis. Genes located on different chromosomes will sort independently.
Define Chi-square Goodness of Fit
A statistical test that indicated the probability that the difference between the observed and expected values is due to chance
What are some assumptions of a chi-square goodness of fit?
Random sample, sample size, independence
Define random sample
the sample data is a random sample of a larger population
Define sample size
is sufficiently large to prevent small sample error
Define independence
observations are independent of each other
Define degrees of freedom
total number of things that could of happened minus 1
What chi square value indicates significance?
below .5
What does a chi square value of .5 or below indicate?
What was observed was not due to chance
Short answer question. How are the principle of segregation and independent assortment related and how do they differ?
Genes encoding different characteristics separate and assort INDEPENDENTLY of one another when they are not located close together on the same chromosome. During this process, 2 alleles of the same gene encoding one characteristic still have to be segregated from each other during the formation of gametes.
What is the problem with multiple testing?
Multiple simultaneous statistical tests increase the chance of finding a false positive since so many variables were tested.
How do we deal with the problem with multiple testing?
Multiple testing correction
Define multiple testing correction
re-calculating probabilities from the multi repeated test. We make the threshold to achieve significance harder to achieve to avoid false positives.
