The human Y chromosome has about 58 million base pairs and about 200 genes, 72 of which currently are known to code for proteins. There is considerable disagreement about the human X chromosome. Most articles suggest an overall length of about 153 million base pairs with between 800 and 900 protein coding genes and between 800 and 1400 other genes (RNA genes, pseudogenes and so on). Since Y chromosomes in humans are significantly shorter than X chromosomes it has been brought to my attention that ALL male martial artists got most of their DNA from their mothers.
The platypus (Ornithorhynchus anatinus) has 26 pairs of chromosomes in total, compared with the 23 pairs present in humans. But researchers had long been confused about which ones are autosomal (inherited equally by males and females), and which ones determine sex. Most of the time for humans two full copies (XX) of the arbitrarily numbered chromosome 23 is a female and one full and one partial copy (XY) is a male. One serious consequence for males of this arrangement is that any genes with challenges on the the unmatched regions of the X chromosome cannot be compensated for – there’s nothing there. This can be a very big deal – the X chromosome contains about 155 million base pairs (5% of the human genome), while the Y chromosome contains about 59 million base pairs. In addition there are what are called pseudo-autosomal regions on both the X and the Y. Most of the time in females one X chromosome in each cell is randomly deactivated so what’s available might either be DNA from the father or the mother. The current best guess is that the human Y chromosome contains between 50 and 60 protein-coding genes, and the human X chromosome contains between 800 and 900 protein-coding genes.
Most birds, some fish, some crustaceans (notably the very complicated Macrobrachium rosenbergii, known as the giant river prawn), some insects (butterflies and moths) and some reptiles (the Komodo dragon – Varanus komodoensis) use a ZW system. ZZ is a male and ZW is a female so the female’s contribution determines the sex of the offspring. In our present context the Komodo dragon is interesting because, while it can see objects as far away as 300 meters, its retinas only contain cones, so it is thought to have poor night vision, reasonable ability to distinguish colors, and poor visual discrimination of stationary objects. A tough laboratory subject.
There is some [statistical] dispute about whether I should have separated the totals by type of school, and whether I should use aggregated killed and wounded. I have generally replied that
- we are talking about human beings, not fruit flies or dice
- when multiple bullets are launched in a small classroom it hardly matters whether the velocity at the muzzle is less than or more than 3,000 feet per second.
- likewise, the force (at the muzzle) of let’s say 3,600 foot-pounds will not have much time or distance to dissipate.
- It is always harder to inject more detail back into data than it is to take the detail out. It is trivial to assert school type is not a factor and analyze the entire data set. It would be very tedious for a future researcher to comb through many text files trying to determine what kind of school was involved.
- In that spirit several readers have asked if one can conclude that charter schools are safer than public schools. As charter schools are fairly recent I would suggest that perhaps 10 years of massacres would be a large enough sample to draw a conclusion with let us say 95% confidence. There are some implicit assumptions there that the frequency of massacres will be uniform and that the intensity of the massacres (number of killed and wounded) will be uniform as well.
- Generally, I dislike descriptive and discrete variables as they force one to partition the data. Then is an unfortunate tendency to claim that the presence of a X chromosome with massive deletions [otherwise known as a Y chromosome which often distinguishes males from females in many species] or various mutations of the MCR1 (16q24.3), OCA2 (15q12-q13.1), TYR (11q14.3), LRMDA (10q22.2-q22.3), SLC24A5 (15q21.1), SLC45A2 (5p13.2) and TYRP1 (9p23) genes [involved in melanin production and metabolism. Melanin strongly influences hair, eye and skin color]. I fail to see that the life of a Hispanic-identified woman somehow has a different value that the life of a Pacific Islander male.
- In a similar manner bullets only say “To Whom It May Concern” so I currently fail to see what use it would be to tally students versus aides, teachers, security guards, administrators, first responders, random strangers … Regardless of what one was before a disaster, after the catastrophe there are only dead, wounded and more or less unwounded living.
- That all said, there may well be merit in formalizing a scale for massacres. In geology we have Richter and Volcanic Explosivity Index scales which are logarithmic, so, for example, a Richter 7 is ten times more powerful than a Richter 6.