What statement is true of prions?
a) prions are produced by viruses.
b) prion diseases can be prevented by cooking your meat.
c) prions are abnormally shaped proteins that cause spongiform encephalopathies.
d) there are no prion diseases of humans, although there are several examples in animals.

Prions are abnormally shaped proteins that cause spongiform encephalopathies. (Ans C)

Explanation:

Prions : Prions are proteinaceous infectious particle or misfolded proteins with the ability to transmit their misfolded shape into normal shape protein.  They are also responsible for some neurodegenerative diseases in mammals. They can affect both animals as well as humans.

Prion disease occurs when normal prion protein (present on the surface of many cells) becomes clump (abnormal) in the brain. This accumulation of abnormal protein in the brain can cause disease.

Spongiform encephalopathies also called prion disease. Spongiform encephalopathies affect the nervous system and brain of animals & humans. It is caused by a degeneration of brain tissues giving it a spongy appearance.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.