X染色体の変異率の選択的に有利な減少の証拠
1Department of Genetics, Cambridge, UK. gatmv@mole.bio.cam.ac.uk
Nature
|March 27, 1997
まとめ
歯類はオートソームよりもX染色体での変異率が低いことを示し,男性偏向の変異率と性進化に関する以前の仮定に異議を唱える.
科学分野:
- 進化生物学の進化生物学について
- 遺伝学 遺伝学とは
- 分子進化は分子進化である.
背景:
- 性種における突然変異の割合は,有害な突然変異の減少の利益と忠誠のコストのバランスをとります.
- 選択は,リセシブ変異の半導体発現により,X染色体の低変異率を好む可能性があります.
研究 の 目的:
- ネズミのX関連遺伝子が,オートソーム遺伝子と比較して,より低い進化率を持っているかどうかを調査する.
- 性染色体と自体染色体間の異性変異率の仮説を検証する.
主な方法:
- マウスとラットの33のX関連遺伝子と238の自体遺伝子の同名置換率の比較分析.
- 男性の変異バイアスと浄化選択を含む潜在的な説明の評価.
主要な成果:
- X関連遺伝子は,オートソーム遺伝子よりも,同義代謝の割合が著しく低いことを示した.
- 男性の変異バイアスも,X染色体でのより強い浄化選択も,観察されたより低い率を説明できませんでした.
- 代謝率の有意な違いは,Y関連遺伝子の代謝率と,自体遺伝子の代謝率の有意な違いは見つかりませんでした.
結論:
- ネズミは,オートソームと比較して,X染色体での変異率が低い可能性が高い.
- ネズミの男性バイアス変異率に関する以前の推定値は不正確である可能性があります.
- 性別の進化における男性突然変異率の増加の役割は,再評価を必要としています.
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関連する概念動画
X-linked Traits
In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.
X-Inactivation
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.
X and Y Chromosomes
Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...
X-linked Traits
In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.
Dosage Compensation
In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X and one Y chromosome, whereas C.elegans with one X chromosome is a male, and the one with two X chromosomes is a hermaphrodite.
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...
X-inactivation
The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.
