Gene expression and regulation Flashcards
What are the components of ribonucleotides
- Sugar Ribose
- Nitrogen Bases
- Phosphate backbone
Name the 4 ribonucleotides that are in RNA, and state whether they are purines or pyrimidines
A & G : Purines
U & C : pyrimidines
Is RNA double stranded or single stranded?
Single Stranded
Does RNA have polarity?
yes
Describe similarities and differences between the processes of DNA replication and transcription
- Similarities : Ribonucleotides are added, one by one, to the growing RNA chain; complementary base-pairing
- Transcription differs from DNA replication in several crucial respects. Unlike a newly formed DNA strand, the RNA strand does not remain hydrogen-bonded to the DNA template strand.
What are the main differences between RNA polymerase and DNA polymerase?
- RNA polymerase uses ribonucleoside for phosphates as substrates, so it catalyzes the linkage of ribonucleotides, not deoxyribonucleotides.
- Second, unlike the DNA polymerase involved in DNA replication, RNA polymerases can start anRNA chain without a primer
Messenger RNA (mRNA) Functions
code for proteins
ribosomal RNAs (rRNAs) Functions
form the core of the ribosome’s structure and catalyze protein synthesis
transfer RNAs (tRNAs) Functions
serve as adaptors between mRNA and amino acids during protein synthesis
microRNAs (miRNAs) Functions
- regulate gene expression
- serve as key regulator of eukaryotic gene expression
TATA box
- The TATA box is a key component of many promoters used by RNA polymerase II, and it is typically located 25 nucleotides upstream from the transcription start site.
What allows RNA to be released from the transcription initiation complex and for transcription to begin?
A key step in liberating the RNA polymerase is the addition of phosphate groups to its “tail”. This liberation is initiated by the general transcription factor TFIIH, which contains a protein kinase as one of its subunits
Why must eukaryotic RNAs go through RNA processing before translation can occur?
Transcription takes place in the nucleus, but protein synthesis takes place on ribosomes in the cytoplasm. So, before a eukaryotic mRNA can be translated into protein, it must be transported out of the nucleus through small pores in the nuclear envelope
Where does RNA processing occur?
In the Nucleus
Intron
Noncoding sequence
Exon
Protein-coding sequences
How are introns removed from mRNA?
Introns Are Removed From Pre-mRNAs by RNA Splicing
Codon
Each group of three consecutive
nucleotides in RNA is called a codon
Reading Frames
A reading frame refers to one of three possible ways of reading a nucleotide sequence.
RNA polymerase II
- Eukaryotic cells
- encode proteins and miRNA’s
- require assisstance of general transcription factors to initiate
tRNA synthetase
catalyzes the covalent coupling of an amino acid to a tRNA
Large rRNA subunit
catalyzes the formation of peptide bonds
small rRNA subunit
matches the rRNA to the codon of the mRNA
