Textbook Notes (362,734)
Biology (27)
BIOL 2000 (3)
Chapter 3

# Chapter 3.docx

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School
University of Lethbridge
Department
Biology
Course
BIOL 2000
Professor
Joseph Rasmussen
Semester
Winter

Description
Chapter 3 Independent Assortment of Genes Definitions  Mendel’s second law- During meiosis, alleles at one gene pair segregate independently of alleles of a second gene pair  Dihybrid- an individual heterozygous at two genes  Product rule- the probability that two independent events occur together is equal to the product of their individual probabilities  Sum rule- the probability that either of two mutually exclusive events occurs is equal to the sum of their individual probabilities  Recombinant- a Meiotic output of different genotype than the meiotic input  Parental- meiotic output of the same genotype as the meiotic input  Ascis- a sac that encloses the products of meiosis (ascosproes) in some fungi  Maternal inheritance- inheritance pattern displayed by a gene on an organelle genome (chloroplast or mitochondria); offspring have maternal phenotype and genotype The green revolution in agriculture  Rice, wheat and corn that are shorter, disease resistant  Norman Borlaug- greatest man of the 20 century, awarded Nobel Peace Prize thought to have saved lives of a billion people Mendel’s law of independent assortment  Mendel studied seven phenotypic pairs  What happens if pair of traits are considered together?  Mednel crossed round green seeded individuals (R/r.y/y) by winkled yellow individuals (r/r.Y/Y) ( “.” Indicated gene location unknown)  F1 individuals show dominant traits for both characters- they are heterozygous at both genes o R/r.Y/y= dihybrid  Deriving 9:3:3:1 using a Punnett square  If genes segregate independently of one another, what gametes do we expect and in what frequencies? o ¼ R.Y o ¼ R.y o ¼ r.Y o ¼ r.y  Punnett’s square predicts that random fusion of four gamete types will give rise to a 9:3:3:1 ratio Mendel’s second law  During gamete formation, the segregation of alleles of one gene is independent of the segregation of the alleles of another gene  The product rile predicts 9:3:3:1 ratio from two independent monohybrid (3:1) ratios o Using a branch diagram to derive 9:3:3:1 Test-crossing a dihybrid  Y/y.R/r x y/y.r/r  If a dihybrid is testcrossed, expect the frequency of phenotypes in the test cross progeny to reflect the gamete frequency of the dihybrid  Calculating genotypic ratios: o Genotype rato for F2 of a dihybrid will be 1:2:1 x1:2:1= 1:2:1:2:4:2:1:2:1  Calculating individual probabilities o If only one fusion even results in a particular genotype  Use product rule: the probability of independent events is the product of their individual probabilities  P(yyrr) = ¼ x ¼ = 1/16 o If more then one fusion event results in a particular genotype  Apply both product rule and sum rule  Sum rule: The probability of either of two mutually exclusive events occurring is the sum of their individual probabilities 
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