Question

Spliceosomes are not found in cells of
a. Bacteria
b. Plants
c. Fungi
d. Animals

Answer 1

Within the nucleus of eukaryotes a specific complex of proteins are found which are responsible for splicing introns (non-coding sequence) from pre-m-RNA and join the exons (coding sequence), produce the active form of protein.

Complete answer:

Option A: Bacteria is a prokaryotic cell. Prokaryotic cells are those primitive cells that lack membrane bound organelles like mitochondria, nucleus etc. Though prokaryotic cells lack other organelles, they possess ribosomes. It does not contain spliceosomes. Thus it lacks a spliceosomal pathway.

Option B: Plants are eukaryotic multicellular organisms. Plant cell comprises well developed, complex organelles that are involved in the biological activities of the cells. The organelles which are found in the plant cells are nucleus, mitochondria, Golgi body, chloroplast, ribosomes, vacuoles etc. It carries out spliceosomes within the nucleus. Spliceosomes join the exons by cutting out the introns and form an active protein sequence.

Option C: Fungi is also a eukaryotic cell. Fungi can be both multicellular or unicellular. Most of the fungi are terrestrial. Example: yeas, mushroom etc. Spliceosomes are found in eukaryotic cells. Thus fungi comprises spliceosomes that help in protein splicing.

Option D: Like plants, animals are eukaryotic organisms which comprise several organelles within the cytoplasm. Animals carry out spliceosomes that are responsible for converting the precursor messenger RNA transcript to a mature messenger RNA within the nucleus.

Hence, the correct answer is option (A).

Note: Spliceosomes are composed of 5 small nuclear RNAs and other associated proteins. These 5 small nuclear RNAs are U1, U2, U4, U5, U6. There are two types of spliceosomes found, named major spliceosome and minor spliceosome.