Bootcamp Chapter 6 Flashcards
There is no _____ hydroxyl group on DNA
a) 3’
b) 1’
c) 5’
d) 2’
D
DNA wraps around proteins called _____. This DNA complex is referred to as ______.
histones, nucleosome
Each nucleosome contains _____ histone proteins
a) 6
b) 7
c) 8
d) 9
D
Which histone is responsible for keeping the DNA wrapped around the central histone core?
H1
T/F? Histones are found in both eukaryotes and prokaryotes.
FALSE - not found in bacteria!
Describe how the histones and DNA are able to tightly bind together.
Histones are positively charged while the DNA is negatively charged from the phosphate groups
What chemical process will create for a more loosely packed DNA strand and thus increase transcription levels?
Acetylation
What histone modification processes will decrease transcription?
methylation and deacetylation
Methylation and deacetylation both decrease transcription rates. Differentiate between the two.
deacetylation - condenses DNA
methylation - hides the transcribing DNA
Bacteria have ____ origin of replication, while eukaryotes can have _____
one, several
What is attached at the 5’ and 3’ ends of DNA?
5’ = phosphate
3’ = hydroxyl group
Origins of replication will be found more in (AT/GC) rich segments if DNA because it has fewer bonds and is thus easier to pull apart
AT
DNA Gyrase
DNA gyrase is a subtype of DNA topoisomerase found in bacteria and plants
What relieves tension ahed of the replication fork as helices is “unzipping” the DNA strand?
topoisomerase
Because DNA polymerase can only extend in the 3’ direction of an existing strand, _____ will place a ____ primer at the origin of replication.
DNA polymerase will now have a ______ _____ group to attach free ______ ______.
primase, RNA
3’ hydroxyl, nucleoside triphosphate
DNA polymerase can extend and read in what direction?
extend - 5’ to 3’
read - 3’ to 5’
What signals for termination of DNA replication?
when two replication forks meet or when proteins bind (physically stops replication fork)
T/F? Because DNA polymerase needs an RNA primer in order to extend DNA - a little piece of it is not replicated. These are called telomeres.
TRUE
During initiation of translation, RNA polymerase will travel along the _____ in what direction?
a) noncoding, 3’ to 5’
b) sense strand, 3’ to 5’
c) noncoding 3’ to 5’
d) antisense 5’ to 3’
C
Where does transcription occur in prokaryotes?
How many elements are found in prokaryotic promoters?
cytosol
-10 to -35
What will prokaryotic core RNA polymerase combine with to form the RNA polymerase holoenzyme? What is the holoenzyme’s function?
sigma factor - when the RNA polymerase and sigma factor are bound, this enables it to target promoter sites
Rho-Independent Termination
termination that relies on a sequence of DNA which will cause the RNA transcript to fold into a hairpin loop.
This structure will cause the polymerase to pause and be released.
Rho-Dependent Termination
Rho will move along the RNA transcript in the 5’ to 3’ direction and catch up to polymerase. Once it touches RNA polymerase it will cause displacement and termination
Operon
Function?
when a group of related genes are under the control of one promoter site
ensures that the cell conserves its resources
Operator Region
a sequence of DNA that lies near or within the promoter site; regulatory in function
Name the constituents of the lac operon
lacZ, Y, and A
What does lacl encode for in regards to the lac operon?
How often is this being created?
repressor protein
lac operon is usually inactive, however; lacl is being constitutively expressed - meaning that its always being made
This isomer of lactose will bind to the lac repressor and cause binding of RNA polymerase to transcribe the operon genes.
allolactose
The lac operon will only be activated in what conditions?
When glucose is not available and when cAMP is high
Describe the relationship between cAMP and glucose
inversely related
Which operon in bacteria is an example of a repressible operon?
trp operon
repressible means that is always active unless it’s turned off
How is the top operon repressed?
High tryptophan levels will bind to the repressor protein and activate it
Attenuation
Another way that the trp operon can be repressed; based on the fact that transcription and translation can occur at the same time in bacteria
Which polymerase is responsible for transcribing most eukaryotic genes?
RNA polymerase II
What is the terminator sequence in transcription in eukaryotes?
poly A signal
5’ Capping
7’-methylguanosinne cap is added to the 5’ end of mRNA during ELONGATION; prevents 5’ cap from degradation
Polyadenylation
serves as a signal to prevent degradation by exonuclease
Introns are _____ while exons are _____
spliced, put together
Mneumonic - introns = interruptions, eons = expressed
What structure will splice introns out? What is it made up of?
spliceosome; made up of snRNA. SnRNA and proteins = snurps
Alternative Splicing
different mRNA molecules are made from the same pre-mRNA primary transcript
What RNA molecules will silence gene expression by interfering with complementary base pairing?
siRNA and miRNA
What are the stop codons?
UAA, UAG, UGA
Which types of mutation can cause a frameshift mutation?
insertion and deletion
Point Mutations
These types of mutations are divided into ____, _____ and _____
nucleotide is replaced by a different one
silent, nonsense, and missense
All diseases below result from point mutations, EXCEPT:
a) Huntington’s
b) Cystic Fibrosis
c) Sickle Cell Anemia
d) Tay-Sachs
A
Silent Mutation
Change in DNA codes results in no change in what amino acid the codon codes for
this occurs because there is less strict base pairing between the third base of a codon and anticodon (third base wobble)
Missense Mutation
Distinguish between conservative and non-conservative missense mutations
occurs when the change in the DNA codes results in the codon now coding for a different amino acid
conservative - will not alter chemical properties of the amino acid
non-conservative - mutated aa does not share the same properties as the unmated amino acid
Which mutation will cause the codon to mutate to a stop codon?
How can severity of this mutation be determined?
nonsense mutation
can be determined by where the mutation occurs - not good if it occurs in the middle of a strand
Frameshift Mutation
mutations that affect how the ribosomes will interpret the remaining codons/how it’s read
a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.
What are the DNA repair mechanisms?
DNA polymerase proofreading, mismatch repair, nucleotide excision repair
Which cells are targeted by HIV?
T helper cells/CD4
Conjugation
bacterial DNA transfer through pili ; dependent on F plasmid
Transduction
virus particles transfer bacterial DNA between different bacterial hosts
