麻省理工学院：《动物遗传学 Genetics》课程教学资源（英文讲义）Lecture 8

TETRAD ANALYSIS IN FUNGI Image removed to due to copyright considerations. THE PRODUCTS OF A SINGLE MEIOSIS ARE PACKAGED IN A SAC (ASCUS)

TETRAD ANALYSIS IN FUNGI Image removed to due to copyright considerations. THE PRODUCTS OF A SINGLE MEIOSIS ARE PACKAGED IN A SAC (ASCUS)

THE PRODUCTS OF A SINGLE MEIOSIS A a Haploid X A Diploid A 1st division a Meiosis Image removed to due to copyright considerations

A A a a THE PRODUCTS OF A SINGLE MEIOSIS A a Haploid Diploid 1st division Meiosis X a A A a a A Image removed to due to copyright considerations. A a a A

Mendel 1.Segregation:Equal numbers of A and a .The phenotype resulting from a mutation in a single gene will segregate exactly 2A 2a. Question in Tetradspeak: Does the phenotype segregate2:2? Yes.A and a are alleles of a single gene

Mendel 1. Segregation: Equal numbers of A and a •The phenotype resulting from a mutation in a single gene will segregate exactly 2A : 2a. •Question in Tetradspeak: Does the phenotype segregate2:2? Yes. A and a are alleles of a single gene

HOW DO WE KNOW WHETHER TWO GENES ARE LINKED? A B X a b ● B b B a or B B Parental Non-Parental AB Ditype Ab Ditype AB (PD) Ab (NPD) a b a B a b a B

HOW DO WE KNOW WHETHER TWO GENES ARE LINKED ? X a b A B A A a a B B b b A B A B a b a b B B b A b A a a or A b A b a B a B Parental Ditype (PD) Non-Parental Ditype (NPD)

How do you determine linkage? You cross AB x ab and find in 100 tetrads: 48 PD 52 NPD Are A and B linked?

How do you determine linkage? You cross AB x ab and find in 100 tetrads: 48 PD 52 NPD Are A and B linked?

Mendel 1.Segregation:Equal numbers of A and a .The phenotype resulting from a mutation in a single gene will segregate exactly 2A:2a. .Question in Tetradspeak: Does the phenotype segregate 2:2? Yes.A and a are alleles of a single gene. 2.Independent Assortment(linkage):AB x ab .Tetradspeak:Are PD=NPD Yes“ "No Two genes are unlinked Two genes are linked

Mendel 1. Segregation: Equal numbers of A and a •The phenotype resulting from a mutation in a single gene will segregate exactly 2A : 2a. •Question in Tetradspeak: Does the phenotype segregate 2:2? Yes. A and a are alleles of a single gene. 2. Independent Assortment (linkage): AB x ab •Tetradspeak: Are PD = NPD Yes No Two genes are unlinked Two genes are linked

Independent Assortment (linkage):AB x ab .Tetradspeak:Are PD=NPD Two genes are unlinked Two genes are linked

Independent Assortment (linkage): AB x ab •Tetradspeak: Are PD = NPD Two genes are unlinked Two genes are linked

Complete Linkage of Two Genes ●AB X ●ab AB AB ab Parental ditype AB AB AB AB ab ab ab ab

Complete Linkage of Two Genes AB X ab AB AB ab ab AB AB ab ab Parental ditype AB AB ab ab

The Products of a Single Crossover ●A B X ● a b B AB Parental B Ab Recombinant a b aB Recombinant b ab Parental TETRATYPE

The Products of a Single Crossover A B a b X A B AB Parental A B Ab Recombinant a b aB Recombinant a b ab Parental X TETRATYPE

2.Independent Assortment(linkage):AB x ab .Tetradspeak:Are PD=NPD Yes No Two genes are unlinked Two genes are linked TETRATYPE? Yes NO 100%linked Map Distance centiMorgans 1/2TT TOTAL

2. Independent Assortment (linkage): AB x ab •Tetradspeak: Are PD = NPD Yes No Two genes are unlinked Two genes are linked TETRATYPE? Yes NO 100% linked Map Distance = 1/2 TT centiMorgans TOTAL