Paper · 1951 · The Japanese Journal of Genetics

Recombination of chromosome segments through continued self-fertilization and the degree of homozygosis to be expected

Moto Kimura

6
claims
11
verbatim quotes
0
citations
1
research areas
✓
Open access

Abstract

1) The behaviour of chromosome segments under continued self-fertilization was discussed from the stand-point that a chromosome composed of innumerable segments rather than particle genes, is divisible by crossing-over.2) Let AA' be the initial chromosome pair whose genetical length is 100x0 units, and designate the length of homozygous segments derived from A and A' as 100LA and 100LA' units respectively and that of heterozygous segment as 100Lh units, so that at any generation LA+LA'+Lh=x0.3) In the n times self-fertilized populations, the frequency of AA' pair is(1-x0)2n/2n, and the frequency (fn(x)dx) in which Lh lies between x and x+dx (0<x< x0) is given as the solution of the following equation, the initial condition of which is f1(x)=2-x0, fn(x)=(1-x)2/2fn-1(x)+∫x0x(2-ξ)fn-1(ξ)dξ+(2-x0)(1-x0)2(n-1)/2n-14) The frequency of heterozygous pairs at the nth generation, Hn=∫x00fn(ξ)dξ+(1-x0)2n/2n, is approximately1+2nx0/2n, when x0 is small, and will be approximate tonx0/2n-1, when n is large.5) In table 1 the figures of Hn are given for the initial 20 generations assuming that the chromosome length is 100 units. From these values, the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes can be easily constructed (Fig. 2). If m=7 the frequency of heterozygous plants is less than 3 in 10000.6) After sufficient generations have elapsed and all the chromosome segments reached the state of fixation, the population contains three kinds of pairs, namely AA, A'A' and the recombined homozygote.The frequency of AA and A'A' are both equal to1/2e2-x0, and in the recombined homozygotes the frequency in which LA'x0 lies between t and t+dt isφ(t)dt=x0e-2x0{2I0(4x0√<t(1-t)>)+I1(4x0√<t(1-t)>)/√<t(1-t)>}dt, where I0 and I1 are Bessel functions.In figure 4 the frequency distribution is given by means of histogram for the chromosome whose genetical length is 100 units.

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Claims 6

Observationobservedoriginal resultsimulated

Claim · model-written summary

Under continued self-fertilization, the frequency of heterozygous pairs at generation n is approximately 1+2nx0/2n when x0 is small.

Taxon
plantsViridiplantaee2
Outcome
frequency of heterozygous pairs at the nth generatione1
Value
1+2nx0/2ne1
Qualifier
when x0 is smalle1

Not reportedDirection

Verbatim

e1

“The frequency of heterozygous pairs at the nth generation, Hn=∫x00fn(ξ)dξ+(1-x0)2n/2n, is approximately1+2nx0/2n, when x0 is small, and will be approximate tonx0/2n-1, when n is large”

✓ located verbatim in the source · abstract, characters 824–1007 · show in text ↑
e2

“the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes”

✓ located verbatim in the source · abstract, characters 1150–1242 · show in text ↑
Observationobservedoriginal resultsimulated

Claim · model-written summary

Under continued self-fertilization, the frequency of heterozygous pairs is approximately nx0/2^(n-1) when n is large.

Taxon
plantsViridiplantaee2
Outcome
frequency of heterozygous pairse1
Value
nx0/2n-1e1
Qualifier
when n is largee1

Not reportedDirection

Verbatim

e1

“The frequency of heterozygous pairs at the nth generation, Hn=∫x00fn(ξ)dξ+(1-x0)2n/2n, is approximately1+2nx0/2n, when x0 is small, and will be approximate tonx0/2n-1, when n is large”

✓ located verbatim in the source · abstract, characters 824–1007 · show in text ↑
e2

“the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes”

✓ located verbatim in the source · abstract, characters 1150–1242 · show in text ↑
Observationobservedoriginal resultsimulated

Claim · model-written summary

With seven pairs of such chromosomes, the frequency of heterozygous plants is less than 3 in 10000.

Taxon
plantsViridiplantaee3
Outcome
frequency of heterozygous plantse3
Direction
less thane3
Value
3 in 10000e3
Qualifier
If m=7e3

Verbatim

e3

“If m=7 the frequency of heterozygous plants is less than 3 in 10000”

✓ located verbatim in the source · abstract, characters 1279–1346 · show in text ↑
Observationobservedoriginal resultsimulated

Claim · model-written summary

The frequency of the heterozygous segment length Lh between x and x+dx is given as the solution of a recurrence equation over self-fertilized generations.

Taxon
plantsViridiplantaee2
Outcome
the frequency (fn(x)dx) in which Lh lies between x and x+dxe4

Not reportedDirection

Verbatim

e4

“the frequency (fn(x)dx) in which Lh lies between x and x+dx (0<x< x0) is given as the solution of the following equation”

✓ located verbatim in the source · abstract, characters 589–709 · show in text ↑
e2

“the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes”

✓ located verbatim in the source · abstract, characters 1150–1242 · show in text ↑
Observationobservedoriginal resultsimulated

Claim · model-written summary

After sufficient generations, AA and A'A' pairs each have frequency 1/2e2-x0.

Taxon
plantsViridiplantaee2
Outcome
frequency of AA and A'A'e5
Value
1/2e2-x0e5

Not reportedDirection

Verbatim

e5

“The frequency of AA and A'A' are both equal to1/2e2-x0”

✓ located verbatim in the source · abstract, characters 1547–1601 · show in text ↑
e2

“the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes”

✓ located verbatim in the source · abstract, characters 1150–1242 · show in text ↑
Observationobservedoriginal resultsimulated

Claim · model-written summary

In recombined homozygotes, the frequency in which LA'x0 lies between t and t+dt is given by a Bessel-function distribution.

Taxon
plantsViridiplantaee2
Outcome
the frequency in which LA'x0 lies between t and t+dte6
Qualifier
in the recombined homozygotese6

Not reportedDirection

Verbatim

e6

“in the recombined homozygotes the frequency in which LA'x0 lies between t and t+dt isφ(t)dt=x0e-2x0{2I0(4x0√<t(1-t)>)+I1(4x0√<t(1-t)>)/√<t(1-t)>}dt, where I0 and I1 are Bessel functions”

✓ located verbatim in the source · abstract, characters 1607–1792 · show in text ↑
e2

“the curves showing the decrease of heterozygosis for plants with m pairs of such chromosomes”

✓ located verbatim in the source · abstract, characters 1150–1242 · show in text ↑