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164 Cards in this Set

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  • Back
How many strands of DNA are copied into mRNA at a time?
only one
What's the central dogma of molecular biology?
DNA (transcription) to RNA (translation) to protein
True/False: Genes can be located on DNA in either orientation.
Some genes are interrupted by ________. This occurs mostly in __________ genes.
True/False: Only one strand of DNA codes for the mRNA.
FALSE! The orientation of the gene determines which strand of DNA codes for the mRNA.
Which are copied into RNA, exons or introns?
BOTH!! The introns are later spliced out before translation.
What is the adaptor that translates a triplet codon in the mRNA into an aa in the protein?
transfer RNA (tRNA)
The amino acids are attached to the tRNA at the ______ end.
3' -OH end
The triplet codons in mRNA are translated into protein on ___________.
The genetic code is universal, non-overlapping, and commaless. It's also __________, meaning that several codons code for the same aa.
The ______ codon is used to initiate translation.
met (AUG)
What are the 3 stop/nonsense codons?
What are Chargaff's rules?
equal amounts of A=T, G=C.
What is different about mRNA?
no introns. it all codes.
The backbone of DNA has the sugar _________ and phosphate linked by ________________.
phosphodiester bond
Name the purines.
Name the pyrimidines.
______(base) is only in RNA.
______ is found in DNA.
The 2 strands in the Watson-Crick DNA double helix are ___________.
It's a right-handed double helix
Base pairing uses what kind of bond?
The hydrophobic _________ are located on the inside of the double helix, the hydrophilic ______________ on the outside.

phosphate and deoxyribose residues
Name 2 forces that hold the double helix together.
1) H bonds
2) pi-electron interactions between the bases (base stacking)
How do you denature DNA? 2 ways.
What is renaturing called?
alkali or heat
What happens if you denature circular DNA?
tangled mesh of strands that can't come apart
What is hyperchromicity effect of DNA upon denaturation?
melting temp of DNA: A=T melts at a lower temp b/c the bonds aren't as strong.
Bases can absorb more light
The cohesive ends of bacteriophage lambda DNA allow ______________.
Usually, you have ________ base pairs per turn of DNA.
If you have + supercoil, you get ______ (more or less?)
less b/c it's overwound, get fewer bp's/turn
How do you fix a supercoil? When do supercoils happen?
during replication
What can produce a supercoil?
intercalation of aromatic compounds into DNA
What is the enzyme that makes the peptide bond?
What are SnRPs? What's a disease involving them?
small RNA nuclear proteins (spliced out of preRNA before mRNA is made)

Lupus is an autoimmune dz against snRPs.
What's required to identify mutant alleles producing a monogenic pattern of inheritance?
a genetic discriminant
What are the 4 subspecialties of medical genetics?
1) cytogenetics (chromosomes)
2) molecular (DNA and mutations)
3) biochemical (analates and sm. molec.)
4) clinical (for MD's)
All diseases have both ______ and __________ mechanisms.
genetic and environmental
Mendelian traits are __________.
Who did x-ray diffraction on DNA to get the structure?
Rosalind Frankin
Mutations are transmitted in families if the __________ is affected.
This effect states that a mutation might be common in a population.
founder effect
How many chromosomes in a normal karyotype?
(23 pairs)
What's the location of a gene?
somatic chromosomes are also called __________.
what is a hemizygote?
inherited one allele on either the X or Y
Who's the person who brought the pedigree to your attention? Does he have to be affected?
Cystic fibrosis is an ____________ inherited dz.
Clues of autosomal recessive (AR):
1) occurs in siblings, parents unaffected
2) males = females
3) parents of affected kid are carriers
4) parents may be consanguinous
5) recurrence risk for each sib in 25% (independent risk)
If both parents are 1/2 normal (heterozygous) for an enzyme, kid will be very low (homozygous). This type of inheritance is..
The Cot value is directly proportional to the ________________.
complexity of the genome.
renaturation kinetics - the more complex, the longer it takes to anneal
The ___________ of the genome does NOT determine its complexity, but rather the ____________________.
% of unique sequences
Highly repetitive sequences (satellite DNA) are located in ____________.
What is satellite DNA?
highly repetitive DNA
What's the repeat sequence unique for human DNA?
Alu sequence
endonuclease site in introns
What's a processed pseudogene?
intermediate repetitive DNA
contain mutations, are reverse transcribed
usually still have the polyA signal (not normally encoded)
DNA is wrapped around a ______________ core like beads on a string.
What is Lyon's hypothesis?
one of the X's inherited in girls gets inactivation/condensation (Barr body), randomly at first, then is set later in progeny
What's Turner syndrome?
45, X
(no barr body)
What's Kleinfelter's syndrome?
YXXXX (3 Barr bodies) infertile
Gene regulation is at the ______________ level.
How do you inactivate a gene?
What does it mean to be "nuclease sensitive"?
in euchromatin, where it's not condensed, nuclease can get in easier for transcription
How many base pairs per turn of DNA?
Where is the highest concentration of DNA found?
sperm heads
Give 2 common mutations
1) deamination of C (methylated)
2) depurination (AP sites) hot spots
What's Werner syndrome?
AR premature aging
can't fix mutations with the usual helicase/exonuclease activity
What is associated w/ all cancers?
different # of chromosomes
DNA replication is _______________.
Replication of circular DNA gives you 2 circles. So now you need ___________, which makes double-stranded cuts.
topoisomerase II
Bacteria and viruses with circular DNA replicate as _____ structures or "__________________."
rolling circles
In cell cycle, DNA synthesis is restricted to the ____ phase.
In prokaryotes, DNA synthesis occurs _________.
at all times
T/F: There's only one site for replication in eukaryotes.
there are many simultaneous sites
(replication bubbles)
DNA polymerase elongates the _______ end of a DNA strand. _________________ are the substrates for DNA polymerase.
deoxyribonucleoside triphosphates
DNA polymerase needs a template and a _________.
E.coli DNA polymerase I has 2 exonuclease activities:
1) 5' to 3' removes RNA primers from Okazaki fragments
2) 3' to 5' proofreads
DNA synthesis at the __________ strand is discontinuous. Synthesis at the __________ strand is continuous. ______________, or short strands of DNA, occur on the ___________ strands.
Okazaki, lagging
RNA is later removed and replaced by DNA bases with the help of ____________.
polymerase I
links the Okazaki pieces
DNA ligase
_____________ relieves the tension so replication can begin. ______________ unwinds the helix (needs ATP to break H bonds).
topoisomerase I
____________ removes primer and proofreads
____________ seals fragments
DNA polymerase I
DNA ligase
During each round of replication, bases are lost at the ends.
Need _____________. Put on by ___________.
telomerase contains ______ which codes for the telomeric repeat.
How do repair enzymes know which strand to fix?
The real (parent) strand gets methylated. DNA restriction endonucleases cut the one that's not methylated.
Name 2 repair deficiencies.
xeroderma pigmentosum

Cockayne syndrome (transcription-coupled repair)
A to G is example of _______ mutation.
A to C is example of _________ mutation.
tautomeric form of adenine pairs with?
deamination of cytosine produces _________.
this causes a ______ mutation.
Name 2 types of DNA repair mechanisms.
1) direct repair
2) excision repair
Methyl-directed mismatch repair by ______________.
dam methylase methylates adenine residues
Give a disorder due to defective mismatch repair.
hereditary nonpolyposis colorectal cancer (NPCC or Lynch syndrome)
What may lead to gene duplication?
unequal crossing over
What happens when both strands of DNA are damaged?
error-prone DNA repair
inducible system
SOS enzymes put in whatever bases it can find
but since only 3% of DNA codes for proteins, it's ok.
How did gene families come about?
crossing over
Branch migration is catalyzed by _______ protein, which allows crossing over.
Phage lambda integration into e.coli is an example of ______________.
site-specific recombination
Recombination of Ig genes to generate antibody diversity is example of _____________.
site-specific recombination
bacterial sex is called ____________
What are conjugative plasmids and what role do they play in hospitalism?
conjugation move from one bacterium to another, transferring antibiotic resistance. R- to R+ plasmid.
What are the simplest mobile genetic elements?
jumping genes or insertion sequences (IS)
When you insert a transposon, you generate ____________.
direct repeats in the target sequence
Eukaryotic cells have a special transposon called a ______________. It's infectious.
What are the 3 clues for autosomal recessive (AR)?
1) consanguinity parents
2) siblings affected (not parents)
3) males = females
What are 2 AR diseases?
cystic fibrosis
sickle cell anemia
What are the 6 clues for autosomal dominant (AD)?
1) males = females
2) every generation
3) affected parent-->offspring
4) heterozygotes are AFFECTED. No such thing as a "carrier."
5) Homozygotes die.
6) isolated cases mean a new mutation
Give 2 examples of AD diseases.
Which inheritance pattern shows male to child transmission (besides Y-linked)?
Which inheritance pattern do you get variable expression?
AD (like NF1; some have cafe' au lait spots, some have neurofibromas)
How do you explain an AD trait skipping generation?
lack of penetrance
Give an example of a sex-limited dz.
male-limited precocious puberty
(familial testotoxicosis)
Give the products of an unaffected female (XX) and an affected male (X*Y) for an X-linked recessive disease.
all daughters will be carriers.
no males will be affected.
X* X*X X*X
For X-linked recessive, can a male be a carrier?
no. he's either affected or not.
Give 3 X-linked recessive (XLR) clues.
1) no male to male transmission
2) mom's brother is also affected (inherited from mom's mom).
3) due to new mutations sometimes
What's Lyon's hypothesis?
inactivated X in females.
which one gets inactivated is random at first, then subsequently fixed.
According to Lyon's hypoth, 50/50 mosaicism is predicted unless there is _______________.
skewed X inactivation
Give an example of a disease where mosaicism can determine phenotype.
Duchenne Muscular Dystrophy in female carriers
skewed x inactivation determines phenotype of XLR disorders
(and calico cats are all female)
Give an example of an X-linked dominant (XLD) disease.
hemophilia (usually lethal if homozygous)
no such thing as "carriers."
Give the 3 XLD clues.
1) affected fathers-->only affect daughters
2) females more than males
3) males usually die if affected (hemizygous)
Give an example of XLD disease.
Rett syndrome (girls)
What does the poisonous death cap mushroom Amanita phalloides do?
inhibit eukaryotic RNA polymerase
(can't synthesize RNA) very deadly
RNA chains are synthesized in the _____________ direction.
5' to 3'
During transcription, the RNA template strand is read in the ___________ direction.
3' to 5'
Does RNA polymerase require a primer?
What goes on the 5' end of new mRNA?
(triphosphate group)
mRNA has to be copied from the ____________ strand in the ____________ direction. RNA is synthesized in the _________ direction.
3' to 5'
5' to 3'
Which RNA polymerase subunit recognizes start sequences (promoters) for transcription?
sigma factor
In the promoter regions, there are usually more _______ base pairs. Why?
A-T b/c it's a weaker bond than G-C
What's a recognition site for initiation of transcription (promoters)?
TATA box
What stimulates transcription upstream from the promoters?
positive regulatory elements (enhancers)
What tells RNA polymerase to fall off and stop RNA synthesis (transcription termination)?
What acts as a transcription terminator and cancer therapeutic? Give an example.
aromatic compounds that intercalate in DNA

actinomycin D and Rifampicin
What makes mRNA and is inhibited by the mushroom poison?
RNA polymerase II
Eukaryotic transcription initiation requires ___________.
DNA-binding proteins can have 3 motifs, which are?
1) helix-turn-helix (phage lambda, CRP)
2) zinc-finger
3) leucine zipper
DNA binding proteins have 2 domains. Name them.
1) DNA binding domain
2) activating domain
Eukaryotic mRNA has a ___________ at its 5' end, and a _______ at its 3' end.
guanosine triphosphate CAP at 5' (which ribosomes require for initiation of translation)

polyA tail at 3' end
How is transcription terminated?
endonuclease cleaves pre mRNA,
mRNA is polyAdenylated at 3' end.
Transcription of rRNA genes is done by _____________ in the ____________.
RNA polymerase I
in the nucleOlus
Stable RNAs are made from precursors, then processed into smaller fragments in the ________.
Polio virus is ___RNA. Would it infect?
+ (like mRNA).
Rabies virus is ___RNA. Would it infect?
-. no.
It would infect if it packaged RNA polymerase and changed itself to +
Reo virus is ____RNA. Would it infect?
+-. No.
Needs RNA polymerase
HIV is ___RNA. Does it infect?
+. yes.
it carries reverse transcriptase.
How can we account for many people with HIV not getting AIDS?
human endogenous retroviruses
What 4 things are needed to synthesize RNA?
1) RNA polymerase
2) promoters (TATA box) w/ sigma factor
3) enhancers
4) Rho-factor for termination
What does eukaryotic RNA polymerase need that prokaryotic doesn't?
What's a common prokaryotic promoter sequence?
TATA box
Which e.coli RNA polymerase subunit dissociates after transcription initiation?
sigma factor
Explain enhancer/UAS.
upstream activating sequences
required for transcription upstream from promoters.
Name 3 methods of prokaryotic transcription termination.
1) rho-factor
2) hairpin turns
3) intercalation by rifampicin
What's the difference b/t prokary. and eukary. mRNA's?
both have 5' GTP cap
but eukary. have 3' polyA tail
How is eukary. mRNA synthesis terminated?
polyA tail at 3' end
Describe transcription of rRNA and tRNA in prok and eukary.
prok: genes occur in multiple copies on precursor molecules that must be processed.
It's a ribozyme: contains RNA instead of polypeptide. Need RNA polymerase to make all cellular RNAs.

euk: rRNA is transcribed by RNA polymerase I in the nucleOlus.
tRNA transcribed by RNA polymerase III, processed by ribunuclease III.
How does the mushroom poison work?
it contains alpha-amanitin, which inhibits RNA polymerase II.
treated with aucubin
What's lupus (SLE)?
autoimmune dz against SnRNPs
malar butterfly rash
What causes beta thalassemia? What selective advantage do they have?
incorrectly spliced mRNA
(RBC's do not have DNA; just proteins for carrying oxygen)
mRNA is more stabile in humans or e.coli?
humans (10 hrs. vs. 5 minutes)
it's stabile RNA (like tRNA and rRNA)
Where do you splice mRNA?
donor and acceptor splice sites
they have consensus sequences
like "GU" and "AG"
___________ in _____________ catalyze the splicing of mRNA. How?
SnRNP's in spliceosomes
-bind to 5' splice site
-lariat formation (branched RNA)
-5' cleavage, release, broken down
-mature RNA remains
How can abnormal processing in the beta globin gene cause beta thalassemia?
RNA mutations in INTRONS can cause mutations because of incorrect splice sites
How do you get more than one protein from the same gene?
alternate splicing
all tRNA have ______ at 3' end.
Introns in mitochondrial genes are self-splicing, that is, they function as ___________.
polyA tails play a role in ?
translation regulation
Describe 3 regions of type II introns (mRNA) that are highly conserved/required for splicing.
1) donor splice site at 5' end
2) acceptor splice site at 3' end
3) branch site at intron/exon boundaries AG:GU
What is RNA editing?
2 forms of apo-B
liver: apo-B100
intesting: apo-B48 b/c has UAA (a stop codon) instead of CAA
posttranscriptional editing
so you get a shorter version in the gut.