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PLNT3140 Introductory Cytogenetics
Lecture 23, part 3 of 3

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III. EVOLUTION OF INTERSPERSED REPETITIVE DNA

A. Global models of genome organization

    cells grown in 3H-UTP    unlabeled wheat, barley, rye or
                  |                          | oat DNA
                  |                          | 8000x excess
shear DNA to a  |                          | shear to 300-400bp
range of sizes  |                          | 
                  |                          |
                  ----------------------------
                                 | reanneal to C0t=120
                                 v
          measure duplex DNA by HAP chromatography
             Do all possible pairwise annealings.


In the graphs above, an excess of unlabled DNA from each of the four species was hybridized with a range of labeled probes. The probes consisted of in-vivo labeled DNA, extracted from cells in culture which were fed radio-labeled nucleotides. Labeled DNA was sheared to a range of size classes, up to 1000 bp. In separate C0t experiments, each probe was hybridized with unlabeled DNA from one of the four species.

Group


Species

I

II

III

IV

V

VI

VII

Wheat

22 (3.8)

10 (1.7)

26 (4.5)

16 (2.8)

-

-

-

Rye

19 (1.6)

19 (1.6)

14 (1.15)

-

22 (1.8)

-

-

Barley

20 (1.1)

23 (1.3)

-

-

-

28 (1.8)

-

Oats

17 (2.2)

-

-

-

-

-

58 (7.7)



B. Variations in specific middle repetitive families

Dowsett, A. P. (1983) Closely related species of Drosophila can contain different libraries of middle repetitive DNA sequences. Chromosoma 88:104-108.

"Very few of the middle repetitive DNA sequences found in Drosophila melanogaster are present in all of the species of the Drosophila subgroup."

D. melanogaster cloned repetitive sequences were used as probe against DNA from other Drosophila species.

From: Dowsett, A. P. (1983) Closely related species of Drosophila can contain different libraries of middle repetitive DNA sequences. Chromosoma 88:104-108.

From: Dowsett, A. P. (1983) Closely related species of Drosophila can contain different libraries of middle repetitive DNA sequences. Chromosoma 88:104-108.

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PLNT3140 Introductory Cytogenetics
Lecture 23, part 3 of 3

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