Cells and Cell Organelles

Question 1

What is the nucleolus?

Answer 1

The site where rRNA is synthesized, and the assembly site of small and large ribosomal subunits

Question 2

Describe the ribosome assembly process in the nucleus

Answer 2

1) Proteins are imported to the nucleus, and delivered to the nucleolus
2) These proteins are assembled into pre-RNA (long strands of rRNA)
3) The pre-RNA is cleaved to form rRNA
4) rRNA is assembled to form the 40s and 60s ribosomal subunits
5) Subunits are exported to the cytoplasm

Question 3

How do histones pack DNA so tightly?

Answer 3

Histones are edged with basic amino acids (arginine and lysine) that facilitate binding to the negatively charged DNA. They then continuously curl, until they reach densely packed chromosomal states

Question 4

How do the various types of histones function in the packing process?

Answer 4

H1 histones functions to seal the nucleosome core particle, while H2A, H2B, H3, and H4 are wrapped by DNA to form the nucleosome core particle