mol bio exam 5 random terms

thymine

which base pair is not present in mRNA and is replaced with uracil?

5' to 3'

which direction is mRNA built in?

downstream

direction of transcription

upstream

opposite direction of transcription

promoter to terminator

which direction does transcription occur in with respect to the promoter and terminator?

initiation, elongation, termination

three stages of transcription

TATA box

A promoter DNA sequence crucial in forming the transcription initiation complex, located upstream from the promoter

transcription initiation complex

The completed assembly of transcription factors and RNA polymerase bound to a promoter.

untwists DNA and exposes 10-20 base pairs at a time, adds bases to 3' end of growing chain

functions of RNA Polymerase II

RNA polymerase will detach when inverted repeats create a stem-loop structure and run of uracils

how is DNA transcription terminated in prokaryotes?

15 nucleotides downstream from poly-adenylation sequence, proteins cut associated with growing transcript cut it free

how is DNA transcription terminated in eukaryotes?

no

does rna splicing occur in prokaryotes?

a modified guanine is added to the front (5') end after 20-25 nucleotide have been synthesized

5' cap

50-250 adenine nucleotides are added to the back (3') end after the polyadenylation site

poly-A tail

amioacyl-tRNA synthetase

enzyme that matches correct amino acid to tRNA

3rd

which codon position is more flexible in its base pairing and may code for the same amino acid?

A-site

holds the new amino acid to be added to a chain in the ribosome

P-site

holds the growing polypeptide chain in the ribosome

E-site

where the empty tRNA molecule leaves on the ribosome

small ribosomal subunit binds to the initiator tRNA (methionine) at the 5' cap

first step of initiation in translation

large subunit binds and forms translation initiation complex

second step of initiation in translation

initiation factors and GTP

what is also needed to form the translation initiation complex?

P site

where does the first tRNA sit during initiation?

5' end; reads from 5' to 3'

where does mRNA begin in the ribosome, and which direction is mRNA translation in?

elongation factors and GTP

what is also needed during elongation of translation?

steps 1 and 3

which steps of translation require GTP for energy?

AUG

start codon

release factor protein binds to stop codon, polypeptide chain is added to water molecule and causes release of peptide chain, 2 GTP molecules are used to dismantle ribosomal machinery

what happens when a stop codon reaches the a-site?

attachment of sugars, lipids, or phosphate groups, cleavage of amino acid into multiple parts, removal of one or more AAs from leading strand

name 3 post-translational modifications that could be made to a polypeptide chain

insertion and deletion

frameshift mutations

missense and nonsense

what are the two types of base substitution mutations?

nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

polyribosomes

Strings of ribosomes that work together to translate a RNA message.

no change to DNA structure, heritable through mitosis, responsive to environment, reversible

what are the advantages of epigenetic regulation?