EXAM 2- CH 6, 7, 9 Flashcards
What question was answered in the Meselson and Stahl experiment
that DNA was semi-conservative
materials used in Meselson and Stahl experiment
- bacteria
- 15N (heavy)
- 14N (light)
procedure of Meselson and Stahl experiment
- grew bacteria in 15N medium and then put bacteria in 14N medium
- centrifuged bacteria
results of Meselson and Stahl experiment
- found that more 14N was found in the DNA of the bacteria with each generation
- DNA replication is semi-conservative
true or false: DNA Replication is fundamentally similar in eucaryotes and bacteria
true
what are the 3 phases of replication
- initation
- elongation
- termination
what occurs in the initation phase of replication
- DNA synthesis begins at ori’s
- formation of replication bubble
what occurs in the elongation phase of replication
polymerization of leading and lagging strand
what occurs in the termination phase of replication
eukaryotes: ends of chromosomes are replicated
function of initiator proteins
- bind to ori to initiate DNA replication
- brings DNA helicase to the region
function of DNA polymerase
- polymerize DNA 5’ —> 3’ direction
- removes RNA primer (exonuclease activity)
- proofread
function of DNA ligase
- forms covalent bonds between nucleotides in the lagging strand
- glue
function of DNA primase
- synthesizes RNA primers
function of DNA helicase
- breaks h bonds between the parent strands
- sizers
function of SSBP
- keeps the single lagging strand separated
- avoids internal hybridization
function of sliding clamp
- protein that keeps DNA polymerase from falling off
- seatbelt
function of clamp loader
- loads the sliding clamp onto DNA
function of topoisomerase/gyrase
- unwinds DNA supercoiling
- cuts phosphodiester bond in backbone
- conditioner
how many forks are there in a replication bubble
2
what nucleotides are by the ori
lots of A and T
why is the ori rich in A and T
less h bonds to break
how many primers are required on the leading strand
1
how many primers are required on the lagging strand
a lot
what is the template in DNA replication
parent strand
what is DNA replication bases on
complimentary basepairs
the leading strand starts replication at what
from primer
how long is a primer
10 nucleotides
function of primer
provides OH end for DNA polymerase on the lagging strand
true or false: DNA helicase does not use ATP
False
true or false: clamp loader uses ATP
true
how many polymerases are needed in prokaryote replication
3
how many polymerases are needed in eukaryote replication
5
how many types of SSB proteins are needed in prokaryote replication
1
how many types of SSB proteins are needed in eukaryote replication
3
how many ori in prokaryotes
1
how many ori in Eukaryotes
many and replicate at different times
findings of the radioactive signals on Chromosomes
- some sequences allowed replication of plasmid —> grew histidine lacking medium
- Most did not
effects in the integrity of cells can lead to what
cancer
what enzyme solves the problem of chromosome shortening
telomerase
how does telomerase solve chromosome shortening
- has an RNA template built into it
- adds more simple sequence repeats to ends of chromosome
DNA replication labeling picture
google slide
the average number of nucleotides added each time enzyme binds to primer–template junction.
Processivity
true or false: the older a cell is the shorter the telomers will be
true
true or false: DNA replication results in the copying of a DNA molecule.
true
true or false: The replication fork in DNA replication is the junction between the newly separated template strands and the unreplicated duplex DNA.
true
true or false: Proofreading exonuclease degrades DNA starting at 5’ ends?
false
what caused the lamb with cyclopia to be deformed
mom ate corn Lilly early in pregnancy
why does corn Lilly cause birth defects in lambs
it shuts down the expression of certain genes
what chemical did moms take to help with morning sickness caused birth defects in babies in the 1960s
thalidomide
mistakes during DNA replication can cause what
mutations
alter the DNA during replication and affect proteins
mutations
substances or energy source that can cause mutations, appear to be linked to cancer
mutagens
what effect do mutations have in germ line cells
- they will be passed on to generations
- they are important for evolutionary change
what effect do mutations have in somatic cells
- passed down to all other somatic cells
true or false: DNA damage delays progression of the cell cycle
true
what are the defects of someone with Xeroderma pigmentosum (XP)
- skin cancer
- UV sensitivity
- neurological abnormalities
what causes Xeroderma pigmentosum (XP)
Nucleotide excision - repair
what are the defects of someone with BRCA2
- breast, ovarian, and prostate cancer
what causes BRCA2
repair by homologous recombination
what are the 3 types of repair mechanisms in a single strand break
- mismatch repair
- base excision repair
- nucleotide excision repair
what are the 2 types of repair mechanisms in a double strand break
- non homologous end-joining
- homologous recombination
- removes errors that escapes proofreading
- scans for distortions in DNA shape
- cuts backbone far away from mutation
- removes nucleotide fragment
- insert correct nucleotide
- ligation
steps of mismatch repair
- Scans double helix for wrong base
- clips out base
- cuts backbone
- remove sugar-phosphate
- inserts correct nucleotide
- ligation
steps of base excision repair
- cuts phosphodiester bonds in single strand
- breaks h bonds
- removal of nucleotides
- synthesizes nucleotides
- ligation
steps of nucleotide excision repair
what is the most dangerous form of DNA damage
breaks in chromosomes with loss of genetic material
specific DNA sequences that have the ability to move within and out of chromosomes are called
transposons
which nuclease cuts in the middle of the DNA strand
endonuclease
uv light primary damages DNA by
forming pyrimidine dimers
which is an easier process non homologous end joining or homologous recombination
NHEJ
true or false: in homologous recombination no DNA is lost
true
what enzyme is used in mismatch repair
mut
what enzymes are uses in base excision repair
- glycosylase
- endonuclease
what enzyme is used in nucleotide excision repair
- UvrABCD
transposons
- mobile genetic elements that can insert into any DNA sequence
- unique and defined sequence
where are transposons found
heterochromatin
how did Barbara McClintock discover transposable elements
- using yellow and purple corn
what is the major difference between class I and II transposons
- class I uses DNA and class II uses DNA and RNA
what transposon uses reverse transcription
class II
what RNA structure is linear
primary
what RNA structure is folds into itself
secondary
what RNA structure has phosphodiester bonds
primary
what RNA structure has h bonds
secondary
what is an example of a secondary RNA structure
tRNA
function of snRNAs
splicing of pre-mRNA
function of snoRNAs
modify rRNAs
where are snRNAs found
nucleus
where are snoRNAs found
nucleolus
where are miRNAs and siRNAs found
- cytosal
function miRNAs
block translation
function of siRNAs
- turn off gene expression
- direct degradation of selective mRNAs
what does transcription generally produce
RNA
in prokaryotes what does transcription produced
- RNA
- mRNA
in eukaryotes what does transcription produced
- primary transcript RNA
- pre-mRNA
- nuclear RNA
true or false: only some portions of DNA sequence are transcribed into RNA
true
what tells DNA to tell RNA polymerase where to start and stop
signals
promoter region
DNA not transcribed
Rna transcripts are _______ and ______ to the template strand of DNA
- complementary
- antiparallel
where does transcription take place in eukaryotes
nucleus
where does transcription take place in prokaryotes
cytosol
what is the transcriptional unit in prokaryotes
polycistronic
what is the transcriptional unit in eukaryotes
monocistronic
several genes are transcribed from a single promoter
polycistronnic
one gene is transcribed from a promoter
monocistronic
function of RNA polymerase I
transcribes large rRNA genes
function of RNA polymerase II
transcribes protein-encoding genes
function of RNA polymerase III
transcribes small RNAs
How does the RNA polymerase know where a gene starts
promoter region
how does the RNA polymerase know which strand is the template
only the template strand has the promoter sequence
which kind of promoters are close to the start of transcription
core promoters
prokaryotes core promoter
TATA box
eukaryotes core promoters
BRE, TATA box, DPE
what type of promoter is usually further from initiation
regulatory promoter
what type of regulatory promoter has an activator bind to up regulate transcription
enhancer regulator promoter
operator or silencer regulatory promoter
DNA that binds a repressor to down regulate transcription
what are 3 characteristics of RNA
- single stranded
- supar- ribose
- Base U
requirements for transcription (Eukaryote )
- activator
- mediator
- chromatin-modifying proteins
