Those parts of a new mRNA transcript that get spliced out and don't wind up getting translated into proteins are called:

a. exons

b. spliceosomes

c. introns

d. protons

The correct answer is c. introns

Explanation:

Newly transcribed mRNA contains coding and non coding sequences. Coding sequences are called exons and non coding sequences are called introns. Introns do not code for proteins and hinder translation so they are removed from the mRNA in a process called splicing.

After splicing of introns from mRNA only exons are left in the mRNA which contains coding region for protein synthesis and are translated into functional proteins.

So introns are parts of a new mRNA transcript that get spliced out and don't wind up getting translated into proteins. Sometimes introns join together to form their own proteins.

Thus, the correct answer is c. introns.