0_Wizard
I am not color blind, but my brother is. Apparently males are more prone to this than females - something to do with the X chromosome.
Males are more likely to be color blind than females, as the genes responsible for the most common forms of color blindness are on the X chromosome.
chosen_Color_blindness_0
Color blindness
chosen_topic_0_Color_blindness
Color blindness
Color blindness, also known as color vision deficiency, is the decreased ability to see color or differences in color. Color blindness can make some educational activities difficult. Buying fruit, picking clothing, and reading traffic lights can be more challenging, for example. Problems, however, are generally minor and most people adapt. People with total color blindness, however, may also have decreased visual acuity and be uncomfortable in bright environments. The most common cause of color blindness is an inherited fault in the development of one or more of the three sets of color sensing cones in the eye.
Dosage compensation
Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order to account for varying numbers of sex chromosomes, different organisms have acquired unique methods to equalize gene expression amongst the sexes. Because sex chromosomes contain different numbers of genes, different species of organisms have developed different mechanisms to cope with this inequality. Replicating the actual "gene" is impossible; thus organisms instead equalize the "expression" from each gene.
X-inactivation
X-inactivation (also called lyonization) is a process by which one of the copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by its being packaged in such a way that it has a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation). The choice of which X chromosome will be inactivated is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism.
Skewed X-inactivation
Skewed X chromosome inactivation occurs when the inactivation of one X chromosome is favored over the other, leading to an uneven number of cells with each chromosome inactivated. It is usually defined as one allele being found on the active X chromosome in over 75% of cells, and extreme skewing is when over 90% of cells have inactivated the same X chromosome. It can be caused by primary nonrandom inactivation, either by chance due to a small cell pool or directed by genes, or caused by secondary nonrandom inactivation, which occurs by selection. Most females will have some levels of skewing. It is relatively common in adult females; around 35% of women have a skewed ratio over 70:30, and 7% of women have an extreme skewed ratio of over 90:10.
Sex differences in human physiology
Sex differences in human physiology are distinctions of physiological characteristics associated with either male or female humans. These can be of several types, including direct and indirect. Direct being the direct result of differences prescribed by the Y-chromosome, and indirect being a characteristic influenced indirectly (e.g. hormonally) by the Y-chromosome. Sexual dimorphism is a term for the phenotypic difference between males and females of the same species. Direct sex differences follow a bimodal distribution. Through the process of meiosis and fertilization (with rare exceptions), each individual is created with zero or one Y-chromosome.
Y chromosome
The Y chromosome is one of two sex chromosomes (allosomes) in mammals, including humans, and many other animals. The other is the X chromosome. Y is the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers testis development. The DNA in the human Y chromosome is composed of about 59 million base pairs. The Y chromosome is passed only from father to son. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome.
X chromosome
The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system. The X chromosome was named for its unique properties by early researchers, which resulted in the naming of its counterpart Y chromosome, for the next letter in the alphabet, after it was discovered later. It was first noted that the X chromosome was special in 1890 by Hermann Henking in Leipzig. Henking was studying the testicles of "Pyrrhocoris" and noticed that one chromosome did not take part in meiosis.