Lecture 3/10 Flashcards
what do release factors do for proks at the end of translation?
cleave the polypeptide chain and disassembles and releases the ribosomal subunits and the tRNA
what are the main differences between prok and euk translation?
in euks the small subunit scans for the 5’ cap and then the Kozak sequence (ACCAUGG) to start translation
in euks, the first amino acid is Met, not fMet
what is important to look for in the Kozak sequence
AUG with C two nts upstream and G one nt downstream to start translation
what helps guide the ribosome to the 5’ cap?
initiation factors
what helps unwind the 2ary structure of RNA
helicase
peptide bond formation occurs when amino acids are in which sites in the ribosome?
P and A
what is the 5’ UTR
the region of the transcript upstream of the initiator codon that doesn’t get translated
what is the 3’ UTR?
the area downstream of the stop codon that doesn’t get translated
are UTRs a specific size?
no, they can be long or short
are UTRs always present? What is their function?
yes, and they’re for stability and contain sequences for regulation
how can there be one transcriptional unit for an operon that encodes multiple proteins?
each gene has its own shine delgarno, AUG, and stop codon
for translation in euks, what does each transcriptional unit need?
its own promoter and enhancer/repressor regions
does each gene need a stop and start codon?
yes! even as part of the same transcript
what is a DNA-dependent DNA polymerase?
template DNA, output DNA (like DNA polymerases)
what is a DNA-dependent RNA polymerase?
DNA template, RNA output (ie. RNA polymerases and primase)
what is a RNA-directed DNA polymerase?
template RNA, output DNA (ie reverse transcriptase and telomerase)
what is a RNA-dependent RNA polymerase?
template RNA, output RNA
what are proteins phosphorylated by?
kinases
what is a phenotype?
observable characteristic
what is an allele?
the alternative possibilities for each gene (every gene has multiple alleles)
what is genotype?
a pair of alleles in a diploid individual
what does +/+ stand for?
WT
what does a/z stand for
het
what does the het phenotype define?
the dominant allele
if +/z are WT phenotype, which allele is dominant?
WT allele
what does a dash represent in a GT? (like +/-)
an unknown GT, so +/- means either +/+ or +/z
what is the result of a LOF mutation?
reduced or abolished protein activity
what is a null/amorphic mutation
a mutation that completely blocks the function of a gene product (ie. deletion of an entire gene or early stop codon)
what is a hypomorphic mutation?
gene product has weak, but detectable activity, may or may not be sufficient
what is haploinsufficient?
one WT allele doesn’t produce enough protein on its own to produce a WT phenotype
where are you most likely to find haploinsufficient genes?
development
what is a trans het?
a WT with a mutated copy or just two mutated copies
are GOF mutations usually recessive or dominant?
dominant
what is a hypermorphic mutation?
it generates more gene product or the same amount of a more efficient gene
why are GOFs bad?
gives you too much protein
where are the mutations that affect the protein itself (ie. making a more efficient gene product) found?
on exons
where would you find the proteins that make more transcript and more protein?
in the regulatory regions
what is a neomorphic mutation?
it generates a gene product with new function or that is expressed at inaproppriate time or place
what is a nonsense mutation
codon for an amino acid is changed to a stop codon
what does the severity of a nonsense mutation depend on?
location on the protein, the earlier it is the worse it will be for protein function
where are nonsense mutations found? why?
exons only! it has to be in the coding region, can’t be in the intron
what happens to many proteins truncated by nonsense proteins?
they might be unstable and therefore degraded since it can’t fold correctly
what do frame shift mutations cause and what are they?
insertion or deletion of a block of one or more proteins from the DNA (not multiples of a codon) and disrupts the translational frame
where are frameshift mutations found?
exons
what are point mutations?
single nucleotide substitutions (either transition or transversion – these can change what the amino acid will be
what kind of mutations don’t alter the gene product/amino acid sequence and why?
silent mutations, and because of wobble!
what are missense mutations?
one amino acid is substituted with another
what are the 2 types of missense mutations?
conservative and non-conservative
what is a conservative missense mutation?
substituted amino acid has similar chemical properties to WT amino acid
what is a non-conservative missense mutation?
substituted amino acid has different chemical properties of WT amino – will change the structure of the protein
Mutations in DNA affect both ______ and ______
RNA and protein
if you disrupt (with a mutation) where something is going to be sliced, that can also disrupt the ______
function
what is an inversion?
a 180 degree rotation of a segment of DNA
when would an inversion mutation occur?
during recombination
what is a reciprocal translation
parts of 2 nonhomologous chromosomes change places, effect depends on whether it’s at the coding region of a protein
are mutations that affect protein levels found in or outside of the protein coding regions? what kinds of mutations are these?
outside! point, deletion, substitution
