Heavy metals only mercury, lead and bismuth meet all of them. Despite this lack of agreement, the term (plural or singular) is widely used in science. A density of more than 5 g/cm is sometimes quoted as a commonly used criterion and is used in the body of this article. The earliest known metals—common metals such as iron, copper, and tin, and precious metals such as silver, gold, and platinum—are heavy metals. From 1809 onwards, light metals, such as magnesium, aluminium, and titanium, were discovered, as well as less well-known heavy metals including gallium, thallium, and hafnium. Some heavy metals are either
Poxvirus AX element late mRNA cis-regulatory element element. Poxvirus AX element late mRNA cis-regulatory element The Poxvirus AX element late mRNA family represents a "cis"-regulatory element present at the 3' end of poxvirus late ATI mRNA and is known as the AX element. The AX element is involved in directing the efficient production and orientation-dependent formation of late RNAs. It is likely that this element directs the endonucleolytic cleavage of the transcript. It has been shown that the F17R late mRNA transcript which is also cleaved is also likely to share a common factor in their mechanism despite a lack of any obvious similarity in its cis-regulatory