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182 Cards in this Set

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  • Back
2 major proc resp for gen variat?
1. mutat
2. recombinat
mutation ______________ playing cards, and ___________________ recombination ____________ playing cards
mutat introduces
recombinat shuffles them
mutagens
cause mutations
excision repair
damamged dna strand is cut out, oth strand is used as templ to remake the damaged one
what is the minimum mutat that can be induced?
point mutation
t or f
its easier to have a loss of funct mutat than a gain of funct mutation
t
new mutat are categorized as/
1. induced
2. spontaneous
what is rate of spont mutat?
one c in 10^5 to 10^8
mutagenesis
prod of mutat thr expos to mutagens
an organ that has gone thr mutagenesis has been?
mutagenized
mutagens have a ______________ dose response
linear
there is always a ___________ level of mutations, even when you are inducing mutations on purpose
background level
2 main types of point mutat are?
1. base subst
2. base addit or delet
base substit are what 2 kinds?
1. transition
2. tranvservion
transition point mutat is?
replacement of A with G
or T with C
replacing a purin with a purin in a mutat is?
transition mut
replac a pyrimidine w a pyrimidine is a?
transition mut
transversion point mutat is?
replac of purine w a pyrimidine
purines are?
A and G
pyrimidines are?
C and T
indel mutat are?
insertion deletion mutat
addit or delet mutat are actually?
addit or mutat of nucleotide pairs
mutat at prot level
a mutat that leads to a diff codon that encodes the same original AA is?
a synonymous mutation
synonymous mutat are also called?
silent mutat
missense mutation is?
codon for one aa is changed to a codon for another aa
also called nonsynonymous mutat
nonsense mutat are?
codon for one aa is ch to a stop codon
synonymous mutat never alter?
the aa seq of polypeptide chain
conservative substit (from a missense mutat)
when an aa is repl wit a chemically similar one
nonconservative substitution (from a missense mutat) is
when an aa is repl w a chem non similar other aa
nonconservat are more likely to prod _______________- in prot struc and funct
severe changes
the closer a nonsense mutat is to the ______________ end of open reading frame the _____________
3' end
more likely that result prot will stil have some biolog activit
nonsense mutat lead to?
premat terminat of translat
indel mutat _________ the reading frame
changes
indel mutation leads to a ___________
frameshift mutation
frameshift mutat is caused by?
an indel mutat
t or f
you can also have mutations in noncoding an regulatory dna like promoters
t
you can have mutat in regulatory regions of dna that can change the level?
of express of a g
just bec you have a mutat on the genotypic leve does not mean you will have one?
on the phenotypic lev
northern blot looks at?
rna
western blot looks at
protein
mutational specificity
mutag tend to do a cert kind of mutat and at a certain spot called hot spot
hot spot
place where a cert mutag tends to makes its mutations
mutagents
3 mech?
1. replace a base
2. alter a base
3. damage a base
base analogs
chemic comp that are so similar to normal nitr bases of dna they are accid incorp into dna struct
tautomers of bases
the diff forms of dna bases that they can naturally take
tautomers of bases
what are the diff forms?
1. keto
2. imino
3. enol
keto, imino, enol
which one is the most common?
keto
what is the change of one tautomer into another called?
tautomeric shift
when a dna base bec ionized it can?
cause a mispair
if A bec its rare imino form it could accid pair w?
C instead of T
name 2 mutagens that alter a base?
EMS and NG
EMS is?
ethylmethanesulfonate
NG is?
nitrosoguanidine
EMS does what to the DnA bases?
it adds an ethyl gr
EMS and NG both add?
alkyl gr to differ positions on the bases
base alteration
when is a mutat most likely to occur?
when the alkyl gr is added to the oxy at posit 6 of guanine to make o-6-alkylguanine
adding an O to posit 6 of guanine leads to what transition?
G C ---> A T
T or F
alkylating agents can ch incoming bases during DNA synth
T
name 3 types of incalating agents?
1. proflavin
2. acridine orange
3. ICR compounds
intercalating agents do what?
flat planar molecules that mimic base pairs and can slip betw nitrogen bases
an intercalating agent like acridine orange
what caused this to happen
acridine orange, ICR-191, proflavin can cause ___________ in the DNA
single nucleotide pair insertions or deletions
if a mutag damages a DNA base it can ___________ DNA synthesis
block
E COli uses what system to bypass a damaged DNA base?
SOS system
t or f
SOS is used only as a last resort
t
DinB , UmuC, and UmuD' are ?
error prone DNA polymerases
EP polymerases are also called?
sloppy copiers or error prone polymerases
the eukaryote system _____________ is similar to E Coli SOS system
translesion DNA synthesis
how do EP polymerases overcome the block in replica?
they add nucleotides to the strand opposite the damaged bases
t or f
error prone polymerases are always present in euk cells
t
error prone polym in E Coli only appear when?
they are induced to by UV damage
SOS mechan
UV light induces the synth of what protein?
RecA
REC A is a key player in?
mechan of DNA repair and recombination
e coli
dna damage
DNA polymerase ________ stalls at site of dna damage
III
e coli
dna ahead of DNA pol III is unwound and bound by ______, and then ___________-
SSB
and then RecA
Rec A and SSB join to form?
protein DNA filament
nist carcinogens like uv and aflatoxin B1 are ___________ mutagens
SOS dependent
name one uv light generated photoproduct?
cyclobutyl ring that unites adj pyrimidines
UV light makes what alterations in DNA?
photoproducts
what is most freq transition causes by UV light?
C ---> T
Aflatoxin B1 comes from?
a fungus assoc w peanuts
apurinic site is where?
in DNA, where the base and the sugar backbone have been separated..
happens with aflatoxin
aflatoxin B1 causes what kind of mutation?
G -C --> T-A transversion
Luria and Delbruck tested?
e coli to with phage T1 to see if any would bec resistant
luria and delbruck
were testing to see if?
the mutations were random or induced by the phage
who came up with the "fluctuation test"
luria and delbruck
luria and delbruck
their experiment suggested that?
resistant e coli cells are select by environm agent (the phage) but not produced by it
replica plating reveals mutant colonies on a __________ thr their behavior on __________
master plate
selective replica plates
replica plating can be used to screen for mutants that?
fail to grow under selective regime
spontaneous lesions are?
naturally occuring damage to dna
what are 2 most freq spont lesions?
depurination and deamination
which is the more common spont lesion , depurination or deamination?
depurination
deamination of cytosine yields?
uracil.
deamination of 5-methylcytosine generates?
thymine. making a C to T transition
DNA analysis of "hot spots" for mutations freq show what base is there?
5-methylcytosine residues
what is another type of spont lesion?
oxidatively damaged bases
name 3 active oxygen species?
O2-, H2O2, and OH radicals
errors in dna replicat can cause?
base substitut
base insert and deletion
in e coli indel can occur at?
repeated seq in dna
e coli
longer repeats are hot spots for?
deletions
common mech respons for genetic diseases is?
expansion of a 3 base pair repeat. called trinucleotide repeat disease.
what is an ex of a trinucleotide repeat disease?
fragile X syndrome
errors in dna replicat can cause?
base substitut
base insert and deletion
in e coli indel can occur at?
repeated seq in dna
e coli
longer repeats are hot spots for?
deletions
common mech respons for genetic diseases is?
expansion of a 3 base pair repeat. called trinucleotide repeat disease.
what is an ex of a trinucleotide repeat disease?
fragile X syndrome
fragile x syndrome results from?
changes in number of a (CCG)n repeat in a region of the FMR-1 gene
(CCG)n repeat in a region of the FMR-1 gene
parents and grandp have increased numb of the repeat so they have?
premutations. cause they dont have the dis yet but they do have increased copy number
fragile X syndrome
(CCG)n repeat in a region of the FMR-1 gene
if you have premutations what will happen?
the repeats will increase a lot more in your offspring
fragile X syndrome
(CCG)n repeat in a region of the FMR-1 gene
what is proposed mechanism?
slipped mispairing in course of DNA synth
Huntington disease is assoc with?
expansion of trinucleotide repeats in a g. huntingtons dis has a repeated seq, often within prot coding regions
Huntington disease and Kennedy disease result from?
amplification of a 3 base pair repeat of CAG
fragile X syndrome
6-59 number of copies.
phenotype?
normal
fragile X syndrome
60-200 number of copies.
phenotype ?
largely normal. this is the premutation stage
fragile X syndrome
>200 number of copies.
phenotype IS?
AFFECTED
FMR-1 g, that are involved in fragile x syndrome, are freq ______ , which is assoc with silenced genes
hypermethylated
dna error free repair
what are 2 ways this happens?
1. repair the damaged base
2. delete the damaged dna and use complem seq as template
direct rev of damag dna
which dam can be revers?
a photodimer caused by uv light
photolyase can repair?
a photodimer caused by uv light
light repair or photorepair uses what enzyme?
photolyase.
why is photolyase a photorepair enzyme?
bec you need cert wavelenghts of light for it to work and repair the damag dna
t or f
photolyase can not work in the dark
t
name 2 dna repair enzymes
1. photolyase
2. alkyltransferase
alkyltransferase is a ?
dna repair enzyme. they can remove alkyl gr from damaged dna
what are 3 types of repair with dam dna?
1. direct rev
2. base excision and replac
3. segm removal and replacement
what are 2 types of homology depend repair systems?
1. excision repair
2. postreplication repair
homolog dep repair syst
excision repair occurs?
before replication
homolog dep repair systems
depend on _____________ of the DNA
complementarity
excision is the ____________ of an entire base
removal and replacement
what enzyme carries out base excision repair?
DNA glycosylase
DNA glycosylase cleaves?
base-sugar bonds
DNA glycosylase generates ___________ sites
apurinic or apyrimidinic
dna glycosylase works with what enzymes?
ap endonuclease
deoxyribophosphodiesterase
dna polymerase
dna ligase
what does ap endonuclease do?
it cuts the sugar phosphate backbone around the site lacking a base
base excision repair ends with _____________ sealing the repaired DNA
dna ligase
there are more ways to damage a base in dna than?
there are glycosylases to remove them. so instead you have to use nucleotide excision repair
nucleotide excision repair system detects?
distortions in the double helix
nucleotide excision repair
e coli
3 enzymes will?
cut the damaged str at 2 sites flanking the lesion
nucleotide excision repair
e coli
the uvr exinuclease cuts out?
8 nucleotides from one side
and 4 from the other
euk
yeasts
nucleotide excision repair is done by?
repairosome
euk
yeasts
repairosome preferentially repairs ?
the template, or transcribed DNA strand
euk
yeasts
repairosome has subunits that are also subunits in the?
basal rna transcription apparatus
name one post replication repair?
mismatch- repair system
mismatch repair system has to do what 3 things?
1. recog mismatched base pairs
2. determ which base is the wrong one
3. excise the incorr base and carry out repair synth
replication errors produce errors on which strand?
the new strand
t or f
normally bacterial dna is methylated
t
post replicat repair
right after replication,
the new bact dna is has not yet been?
methylated
post replic repair
e coli
adenine methylase does what?
it methylates the dna strands.
post replicat repair
e coli
mismatch repair system can work bec it can dist the old strand from the new one by?
the methylation pattern
mismatch repair in hum
it repairs freq errors in what?
short repeat seq (microsatellites)
humans
short repeat seq are also called?
microsatellites
hMutSα and HMutLα fix what kinds of mismatch?
mispaired regions and loops
prok
mismatch repair system corrects errors in replication that are not corrected by?
proofreading function of the replicative dna polymerase.
prok
mismatch repair system
it only fixes the?
newly synthesized strand
repair of ds breaks
how does this occur?
if both str of double helix break at sites that are close to each other
making ds breaks is a normal part of what in a human?
generating antibod diversity
give 2 examples of normal ds breaks?
1. generating antibod divers
2. meiotic recombination
what 2 mech are used to repair ds breaks?
1. non homologous end joining
2. homologous recombination
why is ds repair so hard in a non dividing cell?
bec you dont have anything else to compare it to, like a sister chromatid
ds break
if you dont put the ends back together what could happen?
they could initiate chromosomal rearrangements
non homologous end joining is?
putting the ends back together of a ds break
ds break
what is the proc?
1. KU70, KU80, DNA dep prot kin bind
2 ends are trimmed
3. ends are joined
3
what 3 proteins bind ds in a ds break?
KU70
KU80
large DNA dependeint Prot kinase
homologous recombination is error free bec?
it uses the sister chromatid to repair ds breaks
homolog recombinat
first step?
trimming of 5' ends
homolog recomb
sec step?
broken dna is coated with proteins including RAD51 (a RecA homolog)
RAD51 is involved in?
homolog recombination
RAD51-DNA filament does what after its formed?
searches for the undamaged sequence in its sister chromatid
homol recombin
when RAD51-DNA finds the complementary reg on the sister chrom, what forms?
joint molecule betw the the damaged sister chrom and the undamag sister chromatid
what proteins are involved in repair by homolog recombinat?
1. RAD51
2. DNA Polymerase
3. DNA ligase
In meiosis you can use
a. nonhomologous endjoining
b. homologous recombination
b. homolog recombination
meiosis
crossing over is initiated by?
a ds break
molec mech of crossing over involves what 2 mech?
1. ds break
2. format of heteroduplex DNA
heteroduplex dna is made up of?
one DNA str from one parent and one from another
first evidence for heteroduplex dna came from?
strange ratios in fungi.
in their ascus.
You should have ratio of A:a of 4:4 but you sometimes got 6:2 2:6
what were the aberrant ratios seen in the fungi ascus?
6:2, 2:6
5:3, 3:5
when the ascus had extra copies it was said to have undergone?
gene conversion
ds break model of crossing over
what is the holiday structure?
the formation of what looks like 2 single stranded cross overs
fungus
ascus
ds model of break crossing over
holiday structure are resolved in what ways?
1. vetical breakage
2. horizontal breakage
fungus
ascus
ds break model
if you had no A/a repair you would have a?
5:3 octad
fungus
ascus
ds break model
if you had A/a repair you would have a?
6:2 octad