人間の色覚の分子遺伝学:青,緑,赤の色素をコードする遺伝子
まとめ
人間の色覚は,光に敏感な3種類の色素に依存しています. 遺伝分析により,赤色と緑色の色素の遺伝子がX染色体上に集まっていることが明らかになり,色彩視力の違いが説明されています.
科学分野:
- 遺伝学 遺伝学とは
- 分子生物学は分子生物学である.
- ビジョン ビジョン 科学 科学
背景:
- 人間の色彩視は,光に敏感な3つの異なる色素によって媒介されます.
- これらの色素の遺伝的基礎を理解することは,視覚的知覚を理解するために極めて重要です.
研究 の 目的:
- 人間の色覚ピグメントのアポタンパク質をコードするDNAクローンを分離し,配列化する.
- これらの色素遺伝子の進化的関係と染色体組織を分析する.
主な方法:
- ゲノムと補完的なDNA (cDNA) のクローンの分離とシーケンシング.
- DNAの配列からアミノ酸の配列を引く.
- 進化的関係を決定するための比較シーケンス分析.
主要な成果:
- 染料の推論されたアミノ酸配列は,ロドプシンと約41%の同一性を共有しています.
- 赤色と緑色の色素遺伝子は,青色の色素遺伝子 (43%の同一性) と異なる高い相互同一性 (96%) を表しています.
- 緑色染色体遺伝子の複製数は個体によって異なりますが,赤色と緑色染色体遺伝子はX染色体上のタンデム配列を形成するよう提案されています.
結論:
- X染色体上の赤と緑の染色体遺伝子の遺伝的構造は,ヒトの色覚の変異に影響する可能性がある.
- 赤色と緑色の色素の間の高い配列相似性は,最近の遺伝子複製イベントを示唆しています.
- 青い色素の遺伝子の特異性は,初期の進化の分岐点を示しています.
関連する概念動画
Genetic Lingo
Overview
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”.
Gene Duplication and Divergence
The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are characterized.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are characterized.
Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
Color Vision
Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.


