tetrad analysis - fungal genetics
DESCRIPTION
Tetrad Analysis - Fungal Genetics. Ascomycetes - meiotic spores in ascus Ex. Sordaria , Neurospora , Saccharomyces . perithecium. 1. Tetrad Analysis - Fungal Genetics. Haploid - mycelia or single cells. Tetrad . 2. Life Cycle of Saccharomyces cerevisiae. 3. Unordered Tetrads. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/1.jpg)
1
Tetrad Analysis - Fungal Genetics
Ascomycetes - meiotic spores in ascusEx. Sordaria, Neurospora, Saccharomyces
perithecium
![Page 2: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/2.jpg)
2
Tetrad Analysis - Fungal Genetics
Haploid - mycelia or single cells
Tetrad
![Page 3: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/3.jpg)
3
Life Cycle of Saccharomyces cerevisiae
![Page 4: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/4.jpg)
4
Unordered Tetrads
Saccharomyces cerevisiae
From Al Kapp’s comic ‘Li’l Abner’ 1943
![Page 5: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/5.jpg)
5
Unordered Tetrads
Saccharomyces cerevisiae
![Page 6: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/6.jpg)
6
Ordered Tetrads
Sordaria, Neurospora
Each chromatid- one spore
![Page 7: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/7.jpg)
7
Ordered Tetrads
Sordaria, Neurospora
Each cell from meiosis isrepresented by two identical spores
![Page 8: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/8.jpg)
8
Tetrad Analysis
Evaluate by direct examination or tetrad dissection
Sordaria fimicola
tan, black gray, white
![Page 9: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/9.jpg)
9
Classify Ascus (ordered, unordered) - Spore Phenotypes
Parents crossed: tan x gray t g zygote
Parental ditype (PD)also t g t g, g t t g, etc.
Nonparental ditype (NPD)also b w w b, b w b w, etc.
Tetratype (TT)also b w g t, b t w g, etc.
![Page 10: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/10.jpg)
10
Determining Number of Genes Involved
Parents crossed: tan x gray # genes for color?
![Page 11: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/11.jpg)
11
Ascus Types Expected - Independent Assortment
If Unlinked,
PD = NPD > TT
![Page 12: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/12.jpg)
12
Ascus Types Expected - Linked Genes
PD
TT
PD
More frequent, fewer COs
![Page 13: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/13.jpg)
13
Ascus Types Expected - Linked Genes
TT
TT
NPD
If linked,
PD >> NPD Less frequent, more COs
![Page 14: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/14.jpg)
14
Determining MU Between Linked Genes
![Page 15: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/15.jpg)
15
Distance Between Genes - Sample Problem
![Page 16: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/16.jpg)
16
Distance Between Gene and Centromere
Only possible to determine with Ordered Tetrads
MI segregation MI ascus
MII segregation MII ascus
No CO
CO betweenGene and Cen
![Page 17: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/17.jpg)
17
Distance Between Gene and Centromere
Only possible to determine with Ordered Tetrads
Distance Gene to Cen = 1/2 (# MII asci) x 100 total
![Page 18: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/18.jpg)
18
Distance Gene and CEN - Sample Problem
Where did thecrossovers occur?
Distance:
Aa to Cen?
Bb to Cen?
![Page 19: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/19.jpg)
19
Fungal Genetics - Sample Problem
ClassifyPD, TT, NPD
Linked?PD>>NPD?
Distance:
Kk - Ll
Kk and Cen?
Ll and Cen?
![Page 20: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/20.jpg)
20
Determining Gene Order
MII means CO has occurred between gene and centromere
Relative frequency: Lowest DCO; Intermediate SCO
![Page 21: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/21.jpg)
21
Determining Gene Order
Possible Orders COs required forMII both genes
2 CO
1 CO
1 CO
![Page 22: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/22.jpg)
22
Determining Gene Order
When MII for both is lowest frequency, genes are on opposite sides.
![Page 23: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/23.jpg)
23
Determining Gene Order
When MII for both is intermediate, genes are on the same side.
Which gene is farthest away?
![Page 24: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/24.jpg)
24
Determining Gene Order
MII for both genesIntermediate frequency
MI for inner, MII for outerIntermediate frequency
![Page 25: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/25.jpg)
25
Determining Gene Order - Sample Problem
Number of CO?
![Page 26: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/26.jpg)
26
Ordered Tetrad Analysis - Sample Problem
1. Classify as PD, NPD, TT.2. Classify as MI, MII for each gene.3. Determine linkage, gene order.4. Calculate distances between genes, each gene and centromere.
![Page 27: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/27.jpg)
27
Ordered Tetrad Analysis - Tracking Crossovers
Where did crossoversoccur?
![Page 28: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/28.jpg)
28
Mechanism - Homologous Recombination
Point to point pairing, breakage and rejoining
How does this occur?
![Page 29: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/29.jpg)
29
Mechanism - Homologous Recombination
Model must explain:
1) Conversion Asci
2) CO intermediates observed
![Page 30: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/30.jpg)
30
Holliday Model - Homologous Recombination
First step,nicks in backbones of two ds DNAs
![Page 31: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/31.jpg)
31
Holliday Model - Homologous Recombination
Exchange strands
Strand migration
![Page 32: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/32.jpg)
32
Holliday Model - Resolution of Chiasma
Nick Outer Strands Cross Over Obvious
![Page 33: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/33.jpg)
33
Holliday Model - Resolution of Chiasma
Nick Inner Strands No Cross Over Observed
![Page 34: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/34.jpg)
34
Holliday Model - Resolution of Heteroduplexes
Mispairing within heteroduplexes (hybrid regions)
![Page 35: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/35.jpg)
35
Holliday Model - Resolution of Heteroduplexes
![Page 36: Tetrad Analysis - Fungal Genetics](https://reader033.vdocument.in/reader033/viewer/2022061405/56816598550346895dd87175/html5/thumbnails/36.jpg)
36
Holliday Model - Overview in Text
Box 15.1Russell, 2008Available On Line