DNA-sequence organization in the genome of the domestic chicken (Gallus domesticus)

Abstract

The sequence organization in the DNA of chicken (Gallus domesticus) was studied using hydroxyapatite-monitored reassociation kinetics. DNA 320-nucleotides long reassociates as though it is composed of three components, i.e., a very rapidly reacting fold-back fraction, a component composed of sequences repeated an average of 640 times in the genome, and a large unique fraction representing about 80% of the genome. The sizes of the fold back and repeated components increase only moderately with large increases in fragment size, indicating that these sequences are not extensively interspersed in the genome. Even at a fragment size of 4500 nucleotides, the unique component represents 68% of the DNA. Thus, the chicken genome is not organized in the short-period (Xenopus) interspersion pattern described for a large number of other organisms; rather, the DNA-sequence organization of this vertebrate bears more resemblance to the long-period interspersion pattern of Drosophila.

Organization of Nucleotide Sequences in the Chicken Genome

“…Renaturation kinetics of total DNA obtained here are in agreement with previous reports [15,16], showing a very large proportion of unique sequences (84 %) with only 13 7;…”

Comparative DNA reassociation kinetics of cranes

“…The average crane value is less than thefmr'S for the herring gull [22% (Sibley and Ahlquist, 1983)] and passerines [16% (Shields and Strauss, 1975)] but comparable to those of fowl, duck, and pigeon [11-13% (Arthur and Strauss, 1978;Epplen et al, 1978)] and pheasant and pelican [13% (Wagenmann et al, 1981)]. Rodents appear to have a slightly larger mr fraction (15%) than cranes (Santiago and Rake, 1973).…”

Structural characteristics of genome organization in amphibians: Differential staining of chromosomes and DNA structure

“…Now it has become evident that no such clear-cut universalization exists. For example, genome organization in many birds is apparently quite different (Arthur and Straus 1978;Epplen et al 1978;Ginatulin et al 1979), for more on which see below. Moreover, recent data on the repetitive sequence arrangement in amphibians does not quite agree with the results of the pioneer works.…”

“…In the chicken unique DNA composes 80% of the genome Jimenes et al 1974;Arthur and Straus 1978), but in the genomes of other birds unique DNA content is lower, approximating that in mammals (60-70%) (Shields and Straus 1975;Epplen et al 1978). In the chicken, 7-8% of the genome consist of fast-reassociating foldback sequences, and 11% -of sequences repeating about ten times per genome (Shields and Straus 1978); probably, these fractions were revealed on centrifuation in CsC1 in the form of the satellite DNA.…”