Chapter 14.3-6: tRNA; rRNA; small RNA; noncoding RNA

Question 1

tRNA function

Answer 1

attach amino acids during protein synthesis – each tRNA adds its own amino acid (~74 - 95 nucleotides)

Question 2

What is super rare about tRNA?

Answer 2

Modifed nucleotide bases as a result of chemical changes via tRNA-modifying enzymes.

Ribothymidine
Pseudouridine

Question 3

Transfer RNA structure:

Answer 3

Intermolecular hydrogen bonds
Clover leaf with 4 major arms.
All but acceptor arm are hairpins.

Question 4

tRNA processing

Answer 4

1. Large precursor tRNA is cleaved to make individual molecule
2. Cleaved at usual splice sites, 5’ splice site is at the end of anticodon.
3. CCA bases added to 3’ end
4. Bases modification

Question 5

rRNA

Answer 5

Component of the ribosome, which is mix of proteins & RNAs, some have large subunits, some have small subunits

Question 6

Steps in rRNA processing

Answer 6

1. Methylation attach to bases and 2’-carbon atom of some ribose sugars
2. RNA cleaved into intermediates
3. (Prokarytoes)- Trimmed
4. Mature rRNA

Question 7

What helps to cleave, trim, and modify eukaryotic rRNA?

Answer 7

snoRNAs

Question 8

RNA interference:

Answer 8

limits the invasion of foreign genes and censors the expression of their own genes. (eukaryotes)

Question 9

Functions of siRNA, miRNA (and piRNAs)

Answer 9

1. degradation of mRNA,
2. regulation of gene expression by inhibiting transcription,
3. chromatin modification,
4. defense against viruses.

Question 10

What you need to know about origins, main action, and target of siRNA

Answer 10

Origin: mRNA, transposon, virus

Action: inhibits transcription

Target: genes from which they were transcribed

Question 11

What you need to know about origins, main action, and target of miRNA

Answer 11

Origin: RNA transcribed from distinct gene

Action: inhibits transcription

Target: Genes other than those from which they were transcribed