Crossover interference in humans - PubMed (original) (raw)

Crossover interference in humans

E A Housworth et al. Am J Hum Genet. 2003 Jul.

Abstract

Crossing-over between homologous chromosomes facilitates proper disjunction of chromosomes during meiosis I. In many organisms, gene functions that are essential to crossing-over also facilitate the intimate chromosome pairing called "synapsis." Many organisms--including budding yeast, humans, zebrafish, Drosophila, and Arabidopsis--regulate the distribution of crossovers, so that, most of the time, each chromosome bundle gets at least one crossover while the mean number of crossovers per chromosome remains modest. This regulation is obtained through crossover interference. Recent evidence suggests that the organisms that use recombination functions to achieve synapsis have two classes of crossovers, only one of which is subject to interference. We statistically test this two-pathway hypothesis in the CEPH data and find evidence to support the two-pathway hypothesis in humans.

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Figures

Figure  1

Figure 1

Statistical density functions for intercrossover distances. For the two-pathway model, the density for intercrossover distances is given by

p_2_f*(x|p,0)+2_p_(1-p)[1-F*(x|p,0)][1-F*(x|1-p,m)]+(1-p)2_f_*(x|1-p,m)

and is shown by the solid curve for

_m_=5.5

and

_p_=0.06

(the values estimated for maternal chromosome 2). For the interference-only model, the density is given by

f*(x|1,m)

and is shown by the dashed curve for

_m_=3.2

(the maternal average value under the interference-only model). The dotted curve shows the density for the interference-free model (

_m_=0

).

Figure  2

Figure 2

Cumulative probability for the distance to the next crossover. The cumulative distribution functions for the densities in figure 1 are shown for the two-pathway model with

_p_=0.06

and

_m_=5.5

(solid line), for the interference-only model with

_m_=3.2

(dashed line), and for the interference-free model (dotted line).

Figure  3

Figure 3

Probability of a double crossover in an interval, given no marker recombination—for the two-pathway model with

_p_=0.06

and

_m_=5.5

(solid line), for the interference-only model with

_m_=3.2

(dashed line), and for the interference-free model (dotted line).

Figure  4

Figure 4

Model for recombination rates in humans. The least-squares regression line for the estimation of genetic length from the physical lengths of the maternal (circles) (

X_=0.0125_L+0.241

) and paternal (crosses) (

X_=0.0070_L+0.163

) chromosomes. The maternal analysis includes the X chromosome, whereas the paternal analysis includes only the autosomes.

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References

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