概括
染色体研究显示,美国 marsupials Caluromys derbianus 和 Marmosa mexicana 拥有 14 个染色体,而 Philander opossum 和 Didelphis marsupialis 有 22 个. 这表明有袋动物血统中的独立型进化.
科学领域:
- 遗传学 是一个遗传学.
- 进化生物学 进化生物学
- 哺乳动物学 哺乳动物学
背景情况:
- marsupial 类型表现出显著的多样性.
- 了解染色体进化有助于植物遗传重建.
研究的目的:
- 为了研究四种美国有袋动物物种的染色体特征.
- 为了比较 karyotypes 和推断进化关系.
主要方法:
- 对Caluromys derbianus,Marmosa mexicana,Philander opossum和Didelphis marsupialis进行了理学分析. 这些物种包括:
- 确定双胞胎染色体数量和型形态学的确定.
主要成果:
- 卡洛洛米斯·德比安斯 (Caluromys derbianus) 和墨西哥马尔莫萨 (Marmosa mexicana) 分享了14个染色体的双倍体数,具有相似的型.
- 菲兰德猫头和Didelphis marsupialis具有双倍体数的22个染色体,具有不相似的型.
- 在一些物种中观察到染色体数量从22减少到14.
结论:
- 在C. derbianus和M. mexicana的型是密切相关的.
- P. opossum 和 D. marsupialis 的型是不同的.
- 染色体数量的减少可能在美国和澳大利亚有袋动物群体中独立发生,这表明了融合进化.
相关概念视频
01:39Epistasis
In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence phenotypes in a phenomenon called epistasis. For example, rabbit fur can be black or brown depending on whether the animal is homozygous dominant or heterozygous at a TYRP1 locus. However, if the rabbit is also homozygous recessive at a locus on the tyrosinase gene (TYR), it will have an unshaded coat that appears white, regardless of its TYRP1...
02:32Position-effect Variegation
In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.
01:43Incomplete Dominance
Gregor Mendel's work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid cell has two variants called alleles inherited from each parent. He suggested that amongst these two alleles, one allele is dominant in character and the other recessive. The combination of alleles determines the phenotype of a gene in an organism.
02:27Background and Environment Affect Phenotype
Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
01:19Pigmentation
The color of the skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred to the keratinocytes via melanosomes.
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...