The proposed cause of cjd and kuru in humans, mad cow disease, and scrapie in sheep is a change in a brain protein. disease victims appear to have a protein that should normally contain alpha helices but instead they have changed into a protein made of beta pleated sheets. the disease appears to spread when the abnormal protein comes into contact with the normal protein, causing it to become deformed. which level of protein structure is associated with these diseases?

secondary structure

Explanation:

Alpha helices and beta sheets are two main structural forms in secondary structure of proteins. This structures are formed spontaneously. The next step of protein structure formation is folding into tertiary three-dimensional form.

In diseases such as CJD and kuru, protein prion is changed in structure. It is not known how degeneration of priones protein structure occurs, but it can lead to neurodegenerative diseases which can even be fatal.

Priones are also known as proteinaceous infectious particles.

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.