Stages of mitosis The stages are prophase, metaphase, anaphase and telophase.
The return of Cytogenetics. Meadowfoam meiosis Metaphase I Anaphase I n n 2n Reduction division.
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Transcript of The return of Cytogenetics. Meadowfoam meiosis Metaphase I Anaphase I n n 2n Reduction division.
Meadowfoam meiosis
Metaphase I Anaphase I
a
B
a
b
A
BA
b
Mendel’s second law – law of independent assortment
But what if the genes are on the same chromosome?
Metaphase I Anaphase I
a
B
a
b A
BAb
No independent assortmentDeviation from Mendel’s second law
Creating gene maps
Many genes were mapped to specific chromosomes and specific chromosome arms in wheat and barley before the advent of molecular genetics
How was this possible?
Chromosome mapping
Many genes were mapped to specific chromosomes in wheat and barley before the advent of molecular genetics
How was this possible?
Deviation from Mendel’s laws
If there is a chromosome or part of a chromosome missing the inheritance of any gene on the missing part will deviate from Mendel’s laws
If there is an extra chromosome or chromosome arm the inheritance of any gene on the extra chromosome will also deviate from Mendel’s laws
Combining cytogenetics and molecular genetics for gene mapping
Wheat deletion series – mapping wheat gene locations
Wheat is a hexaploid with 3 genomes A, B and D.The genes are arranged on the same chromosomes in the different genomes, making the chromosomes homeologous (1A, 1B and 1D carry similar genes)
How do you know which chromosome to test?
- Screen plants that carry 4 copies of one chromosome and no copies of a homeologous chromosome (nulli-tetrasomic)
Example: nulli-tetrasomic for chromosome 1D 0 copies of chromosome 1D, 4 copies of either chromosome 1A or chromosome
1B
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Southern blot results with marker used as a probe – what is the chromosome location of the probe?
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Southern blot results with marker used as a probe – probe is on chromosome 1D
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Telo
1D
S
Telo
1D
LSouthern blot results with marker used as a probe – what is the chromosome arm location of the probe?
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Telo
1D
S
Telo
1D
LSouthern blot results with marker used as a probe – Chromosome arm location – 1DS
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Telo
1D
S
Telo
1D
L
Del
1D
S-1
Del
1D
S-2
Del
1D
S-3
Southern blot results with marker used as a probe – what section of chromosome IDS is the location of the probe?
Dis
omic
Nul
li 1A
Nul
li 1B
Nul
li 1D
Telo
1D
S
Telo
1D
L
Del
1D
S-1
Del
1D
S-2
Del
1D
S-3
Gene is on the short arm of chromosome1D in the region covered by deletion 1DS-3
Genome sequencing
- Barley
How can you separate out a specific chromosome for sequencing?
Use differences in chromosome size provided by the presence of telochromosomes in telo-trisomics
Barbara McClintock- cytogeneticist- worked on corn- in the 1940’s worked on a trait that appeared to change locations on a chromosome (inversions) and/or move between chromosomes (translocations)- problem, no observable chromosome changes- so she proposed the idea of transposable elements
Visualization of C genome chromosomes
BC1 between wheat and jointed goatgrass - which species is the recurrent parent?
Count number of yellow chromosomes, greater than 7 – recurrent parent jointed goatgrass
BC1 between wheat and jointed goatgrass - which species is the recurrent parent?