protein synthesis quiz Flashcards
why does the cell need to make RNA?
DNA is housed in the protective nucleus of the cell
- protein synthesis occurs outside the nucleus in the ribosome
- dna is too important to leave the nucleus, and RNA intermediate is needed to bring genetic info outside the nucleus
what is the structure of RNA?
- ribose sugar instead of deoxyribose
- uracil instead of thymine
- can travel between nucleus and cytoplasm
- in protein synthesis (mRNA, tRNA, and rRNA)
central dogma of molecular biology
DNA to RNA to Protein
protein synthesis occurs in what 2 steps
transcription and translation
what 3 stages does transcription and translation occur in
initiation, elongation, termination
what is the initiation stage of transcription
RNA polymerase binds to the DNA at the promoter
what is the elongation stage of transcription
using DNA as a template, binds the mRNA using paired nitrogenous bases (A-U, C-G)
what is the termination stage of transcription
leaves the nucleus
what is the initiation stage of translation
ribosomes binds to mRNA
what is the elongation of translation
- ribosomes mRNA in sets of nucleotides codes called a codon
- each codon translates codes for a different amino acid
what is the termination stage of translation
polypeptide chain created and released
promoter region is usually high in
As and Ts
why are promoter regions high in As and Ts
so RNA polymerase expends less energy opening up the DNA helix (bc its only 2 hydrogen bonds instead of 3)
only 1 DNA strand is used as the..
template strand (3’ 5’)
the strand not used for transcription is known as the….
coding strand (5’ to 3’)
terminator sequence is when…
RNA polymerase recognizes the end of a gene
the primary transcript is known as..
the newly synthesized mRNA that disassociates from the DNA template strand
post transcript modification only occurs in what cells
eukaryotic
what post transcript modifications are made
- 5’ cap and Poly A Tail added to 3’ end
- introns, leaving behind exons
- mRNA is now known as mRNA transcript following all modifications
purpose of 5’ cap
to protect mRNA from digestion by nucleus and phosphatases as it exits and enters cytoplasm, also used to initiate translation
purpose of Poly-A-Tail
added to 3’ end of primary transcript by poly-A-polymerase to protect it from degradation later on
what are introns
non-coding regions
what are exons
coding regions
introns are cut out by what
spliceosomes, which also joins remaining exons together
each triplet of nucleotides is called a
codon
what is the start codon
AUG
what do tRNA do
ribosomes alone cannot synthesize polypeptide chain, tRNA must deliver the correct amino acids to the polypeptide building site
what are anticodons
sequence of 3 bases at the end of one lobe of tRNA
what do anticodons do
written in the 3’ to 5’ direction, and recognizes and is complementary to the codon of the mRNA
- at the end of the strand is an attachment site for the corresponding amino acid specified by the mRNA codons
ribosomes
the site of protein synthesis
- a complex that contains a cluster of proteins and rRNA which are linear strands of RNA
- ribosomes have binding sites for the mRNA transcript and the amino acid (tRNA molecules)
