Unit 4 - Mandelean Genetics Flashcards
What kind of experimental design did mandel use
He uses a modern scientific approach. He had a hypothesis that he used a controlled experiment to test. He gathered data from said experiment and interpertated the data to draw a conclusion
Why did mandell use peas
Because each trait had a dominant and recessive phenotype when mandell created the pure-breeding strains. This allowed mandel to preform many crosses and exhamine many individual plants
F2 ratio for a GG x gg cross
3:1 dominant to recessive (phenotype) and a 1:2:1 (GG, Gg, gg) genotype
The Law of segregation AND Law of Independent assortment
In meiosis I there is 4 allelles present (GGgg for example) these are randomly (independent assortment) segredgated oppon cell division, providing each daughter cell with 2 alleles. (GG, gg for example) When the cells divide agin in meiosis II, the Alleles are once again seperated as the cell forms gametes.(independent assortment) (g, g, G, G) during reporduction, these alleles pair up as homologous - with one allele from the mom and dad each coding for the same gene. Dominant alleles are expressed over recessive, leaving us with a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio
Pratice Brand diagram
Slide 43 lecture 3
Dihybrid cross ratio
9:3:3:1 phenotypic ratio (dominant for both, dominant for 1, dominant for other 1, recessive for both)
The product rule
“And” Questions: the P of two or more independent events is the product of their P’s
P1 (0.23) and P2 ( 0.45) = (0.23 * 0.45)
The Sum rule
“Either or” Questions: the P of two or more mutally exclusive events both occuring is the sum of their P’s
P1 (0.23) and P2 ( 0.45) = (0.23 + 0.45)
Conditonal probabiltiy
*Conditional probability involves questions asked after a cross has been made
ex: for the cross Gg X Gx, yellow seed offspring make up a 3:1 (3/4) ratio of offspring. What is the P that the yellow seeded offspring are heterozygous?
*Yellow cannot be gg therefore we go from 3/4 to 3/3 (remove the gg as its not yellow)
*we know one of those 3 will be GG (1:2:1 ratio), so the P for heterozygous yellow seeds is 2/3!
Binominal probability
*Used to predict the P of a SERIES of events, with each event having at least 2 outcomes.
Equation: (p + q)^2 = 1 where p = the probability of one outcome, q is the probaility of the alternative outcome, and n is the number of sucessive events.
ex: For families with three children, predict the proportions with each possible combination of boys and girls
*𝑝=”probability of a boy”=1/2; 𝑞=”probability of a girl”=1/2, number of events = 3 (because 3 kids)
*Binominal expansion: (𝑝+𝑞)^3=𝑝^3+3𝑝^2 𝑞+3𝑝𝑞^2+𝑞^3
*𝑝^3=1/8 (3” boys”); 3𝑝^2 𝑞=3/8 (2” boys, 1 girl”); 3𝑝𝑞^2=3/8(1” boy, 2 girls”); 𝑞^3=1/8 (3” girls”)
*see slides 61-63 in lecture 3 for a better format
Pratice binominal probaility
find a question on UM learn or google
Chai-squared test
*used to assess if pbserved values are significant by comparing them to expected values.
*Get expected values by taking observed values and multiplying by mandelean ratios
ex: observed for a dominant phenotype is 100 peas, so the expected would be 100(3/4) = 75 peas because dominant trais in a monohybrid cross have a 3:1 (or 3/4) ratio!
*then plug into formula ((observed - expected)^2) / expected = Chai squared value.
*then get your Df = number of outcomes -1. we have 2 outcomes here, dominant or recessive so our df = 1
*take that mad lad to the table to get your p-value
*reject if p < alpha
Gene
unit of heredity
Allele
one or more alternative forms of a gene found at the same location on a chromosome
Oogenesis
production or development of a female gamete
