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164 Cards in this Set
- Front
- Back
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How many strands of DNA are copied into mRNA at a time?
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only one
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What's the central dogma of molecular biology?
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DNA (transcription) to RNA (translation) to protein
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True/False: Genes can be located on DNA in either orientation.
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true
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Some genes are interrupted by ________. This occurs mostly in __________ genes.
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introns
eukaryotes |
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True/False: Only one strand of DNA codes for the mRNA.
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FALSE! The orientation of the gene determines which strand of DNA codes for the mRNA.
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Which are copied into RNA, exons or introns?
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BOTH!! The introns are later spliced out before translation.
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What is the adaptor that translates a triplet codon in the mRNA into an aa in the protein?
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transfer RNA (tRNA)
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The amino acids are attached to the tRNA at the ______ end.
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3' -OH end
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The triplet codons in mRNA are translated into protein on ___________.
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ribosomes
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The genetic code is universal, non-overlapping, and commaless. It's also __________, meaning that several codons code for the same aa.
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degenerate
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The ______ codon is used to initiate translation.
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met (AUG)
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What are the 3 stop/nonsense codons?
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UGA, UAG, UAA
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What are Chargaff's rules?
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equal amounts of A=T, G=C.
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What is different about mRNA?
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no introns. it all codes.
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The backbone of DNA has the sugar _________ and phosphate linked by ________________.
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deoxyribose
phosphodiester bond |
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Name the purines.
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adenine
guanosine |
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Name the pyrimidines.
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Cytosine
Thymine Uracil |
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______(base) is only in RNA.
______ is found in DNA. |
U
T |
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The 2 strands in the Watson-Crick DNA double helix are ___________.
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antiparallel
It's a right-handed double helix |
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Base pairing uses what kind of bond?
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hydrogen
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The hydrophobic _________ are located on the inside of the double helix, the hydrophilic ______________ on the outside.
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bases
phosphate and deoxyribose residues |
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Name 2 forces that hold the double helix together.
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1) H bonds
2) pi-electron interactions between the bases (base stacking) |
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How do you denature DNA? 2 ways.
What is renaturing called? |
alkali or heat
annealing/hybridization |
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What happens if you denature circular DNA?
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tangled mesh of strands that can't come apart
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What is hyperchromicity effect of DNA upon denaturation?
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melting temp of DNA: A=T melts at a lower temp b/c the bonds aren't as strong.
Bases can absorb more light |
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The cohesive ends of bacteriophage lambda DNA allow ______________.
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circularization
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Usually, you have ________ base pairs per turn of DNA.
If you have + supercoil, you get ______ (more or less?) |
10
less b/c it's overwound, get fewer bp's/turn |
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How do you fix a supercoil? When do supercoils happen?
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topoisomerase
during replication |
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What can produce a supercoil?
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intercalation of aromatic compounds into DNA
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What is the enzyme that makes the peptide bond?
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ribozyme
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What are SnRPs? What's a disease involving them?
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small RNA nuclear proteins (spliced out of preRNA before mRNA is made)
Lupus is an autoimmune dz against snRPs. |
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What's required to identify mutant alleles producing a monogenic pattern of inheritance?
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a genetic discriminant
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What are the 4 subspecialties of medical genetics?
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1) cytogenetics (chromosomes)
2) molecular (DNA and mutations) 3) biochemical (analates and sm. molec.) 4) clinical (for MD's) |
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All diseases have both ______ and __________ mechanisms.
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genetic and environmental
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Mendelian traits are __________.
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discontinuous
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Who did x-ray diffraction on DNA to get the structure?
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Rosalind Frankin
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Mutations are transmitted in families if the __________ is affected.
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germline
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This effect states that a mutation might be common in a population.
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founder effect
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How many chromosomes in a normal karyotype?
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46
(23 pairs) |
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What's the location of a gene?
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locus
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somatic chromosomes are also called __________.
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autosomal
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what is a hemizygote?
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inherited one allele on either the X or Y
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Who's the person who brought the pedigree to your attention? Does he have to be affected?
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proband
no |
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Cystic fibrosis is an ____________ inherited dz.
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AR
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Clues of autosomal recessive (AR):
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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) |
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If both parents are 1/2 normal (heterozygous) for an enzyme, kid will be very low (homozygous). This type of inheritance is..
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AR
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The Cot value is directly proportional to the ________________.
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complexity of the genome.
renaturation kinetics - the more complex, the longer it takes to anneal |
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The ___________ of the genome does NOT determine its complexity, but rather the ____________________.
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size
% of unique sequences |
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Highly repetitive sequences (satellite DNA) are located in ____________.
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centromeres
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What is satellite DNA?
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highly repetitive DNA
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What's the repeat sequence unique for human DNA?
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Alu sequence
endonuclease site in introns |
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What's a processed pseudogene?
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intermediate repetitive DNA
NONFUNCTIONAL COPIES OF A NORMAL GENE contain mutations, are reverse transcribed usually still have the polyA signal (not normally encoded) |
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DNA is wrapped around a ______________ core like beads on a string.
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nucleosome
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What is Lyon's hypothesis?
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one of the X's inherited in girls gets inactivation/condensation (Barr body), randomly at first, then is set later in progeny
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What's Turner syndrome?
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45, X
(no barr body) |
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What's Kleinfelter's syndrome?
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YXXXX (3 Barr bodies) infertile
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Gene regulation is at the ______________ level.
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chromatin
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How do you inactivate a gene?
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methylation
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What does it mean to be "nuclease sensitive"?
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in euchromatin, where it's not condensed, nuclease can get in easier for transcription
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How many base pairs per turn of DNA?
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10
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Where is the highest concentration of DNA found?
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sperm heads
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Give 2 common mutations
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1) deamination of C (methylated)
2) depurination (AP sites) hot spots |
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What's Werner syndrome?
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AR premature aging
can't fix mutations with the usual helicase/exonuclease activity |
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What is associated w/ all cancers?
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ANEUPLOIDY
different # of chromosomes |
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DNA replication is _______________.
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semi-conservative
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Replication of circular DNA gives you 2 circles. So now you need ___________, which makes double-stranded cuts.
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topoisomerase II
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Bacteria and viruses with circular DNA replicate as _____ structures or "__________________."
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theta
rolling circles |
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In cell cycle, DNA synthesis is restricted to the ____ phase.
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S
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In prokaryotes, DNA synthesis occurs _________.
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at all times
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T/F: There's only one site for replication in eukaryotes.
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false
there are many simultaneous sites (replication bubbles) |
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DNA polymerase elongates the _______ end of a DNA strand. _________________ are the substrates for DNA polymerase.
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3'
deoxyribonucleoside triphosphates |
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DNA polymerase needs a template and a _________.
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primer
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E.coli DNA polymerase I has 2 exonuclease activities:
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1) 5' to 3' removes RNA primers from Okazaki fragments
2) 3' to 5' proofreads |
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DNA synthesis at the __________ strand is discontinuous. Synthesis at the __________ strand is continuous. ______________, or short strands of DNA, occur on the ___________ strands.
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lagging
leading Okazaki, lagging |
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RNA is later removed and replaced by DNA bases with the help of ____________.
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polymerase I
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links the Okazaki pieces
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DNA ligase
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_____________ relieves the tension so replication can begin. ______________ unwinds the helix (needs ATP to break H bonds).
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topoisomerase I
helicase |
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____________ removes primer and proofreads
____________ seals fragments |
DNA polymerase I
DNA ligase |
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During each round of replication, bases are lost at the ends.
Need _____________. Put on by ___________. |
telomeres
telomerase |
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telomerase contains ______ which codes for the telomeric repeat.
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RNA
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How do repair enzymes know which strand to fix?
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The real (parent) strand gets methylated. DNA restriction endonucleases cut the one that's not methylated.
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Name 2 repair deficiencies.
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xeroderma pigmentosum
Cockayne syndrome (transcription-coupled repair) |
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A to G is example of _______ mutation.
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transition
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A to C is example of _________ mutation.
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transversion
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tautomeric form of adenine pairs with?
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Cytosine
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deamination of cytosine produces _________.
this causes a ______ mutation. |
Uracil
transition |
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Name 2 types of DNA repair mechanisms.
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1) direct repair
2) excision repair |
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Methyl-directed mismatch repair by ______________.
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dam methylase methylates adenine residues
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Give a disorder due to defective mismatch repair.
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hereditary nonpolyposis colorectal cancer (NPCC or Lynch syndrome)
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What may lead to gene duplication?
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unequal crossing over
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What happens when both strands of DNA are damaged?
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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. |
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How did gene families come about?
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crossing over
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Branch migration is catalyzed by _______ protein, which allows crossing over.
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recA
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Phage lambda integration into e.coli is an example of ______________.
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site-specific recombination
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Recombination of Ig genes to generate antibody diversity is example of _____________.
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site-specific recombination
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bacterial sex is called ____________
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conjugation
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What are conjugative plasmids and what role do they play in hospitalism?
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conjugation move from one bacterium to another, transferring antibiotic resistance. R- to R+ plasmid.
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What are the simplest mobile genetic elements?
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jumping genes or insertion sequences (IS)
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When you insert a transposon, you generate ____________.
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direct repeats in the target sequence
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Eukaryotic cells have a special transposon called a ______________. It's infectious.
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retrotransposon
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What are the 3 clues for autosomal recessive (AR)?
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1) consanguinity parents
2) siblings affected (not parents) 3) males = females |
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What are 2 AR diseases?
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cystic fibrosis
sickle cell anemia |
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What are the 6 clues for autosomal dominant (AD)?
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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 |
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Give 2 examples of AD diseases.
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achondroplasia
NF1 |
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Which inheritance pattern shows male to child transmission (besides Y-linked)?
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AD
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Which inheritance pattern do you get variable expression?
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AD (like NF1; some have cafe' au lait spots, some have neurofibromas)
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How do you explain an AD trait skipping generation?
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lack of penetrance
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Give an example of a sex-limited dz.
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male-limited precocious puberty
(familial testotoxicosis) |
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Give the products of an unaffected female (XX) and an affected male (X*Y) for an X-linked recessive disease.
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all daughters will be carriers.
no males will be affected. X X X* X*X X*X Y XY XY |
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For X-linked recessive, can a male be a carrier?
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no. he's either affected or not.
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Give 3 X-linked recessive (XLR) clues.
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1) no male to male transmission
2) mom's brother is also affected (inherited from mom's mom). 3) due to new mutations sometimes |
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What's Lyon's hypothesis?
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inactivated X in females.
which one gets inactivated is random at first, then subsequently fixed. |
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According to Lyon's hypoth, 50/50 mosaicism is predicted unless there is _______________.
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skewed X inactivation
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Give an example of a disease where mosaicism can determine phenotype.
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Duchenne Muscular Dystrophy in female carriers
skewed x inactivation determines phenotype of XLR disorders (and calico cats are all female) |
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Give an example of an X-linked dominant (XLD) disease.
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hemophilia (usually lethal if homozygous)
no such thing as "carriers." |
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Give the 3 XLD clues.
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1) affected fathers-->only affect daughters
2) females more than males 3) males usually die if affected (hemizygous) |
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Give an example of XLD disease.
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Rett syndrome (girls)
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What does the poisonous death cap mushroom Amanita phalloides do?
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inhibit eukaryotic RNA polymerase
(can't synthesize RNA) very deadly |
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RNA chains are synthesized in the _____________ direction.
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5' to 3'
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During transcription, the RNA template strand is read in the ___________ direction.
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3' to 5'
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Does RNA polymerase require a primer?
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no
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What goes on the 5' end of new mRNA?
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PPP
(triphosphate group) |
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mRNA has to be copied from the ____________ strand in the ____________ direction. RNA is synthesized in the _________ direction.
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ANTISENSE
3' to 5' 5' to 3' |
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Which RNA polymerase subunit recognizes start sequences (promoters) for transcription?
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sigma factor
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In the promoter regions, there are usually more _______ base pairs. Why?
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A-T b/c it's a weaker bond than G-C
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What's a recognition site for initiation of transcription (promoters)?
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TATA box
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What stimulates transcription upstream from the promoters?
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positive regulatory elements (enhancers)
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What tells RNA polymerase to fall off and stop RNA synthesis (transcription termination)?
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Rho-factor
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What acts as a transcription terminator and cancer therapeutic? Give an example.
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aromatic compounds that intercalate in DNA
actinomycin D and Rifampicin |
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What makes mRNA and is inhibited by the mushroom poison?
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RNA polymerase II
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Eukaryotic transcription initiation requires ___________.
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enhancers
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DNA-binding proteins can have 3 motifs, which are?
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1) helix-turn-helix (phage lambda, CRP)
2) zinc-finger 3) leucine zipper |
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DNA binding proteins have 2 domains. Name them.
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1) DNA binding domain
2) activating domain |
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Eukaryotic mRNA has a ___________ at its 5' end, and a _______ at its 3' end.
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guanosine triphosphate CAP at 5' (which ribosomes require for initiation of translation)
polyA tail at 3' end |
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How is transcription terminated?
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endonuclease cleaves pre mRNA,
mRNA is polyAdenylated at 3' end. |
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Transcription of rRNA genes is done by _____________ in the ____________.
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RNA polymerase I
in the nucleOlus |
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Stable RNAs are made from precursors, then processed into smaller fragments in the ________.
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nucleus
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Polio virus is ___RNA. Would it infect?
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+ (like mRNA).
yes |
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Rabies virus is ___RNA. Would it infect?
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-. no.
It would infect if it packaged RNA polymerase and changed itself to + |
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Reo virus is ____RNA. Would it infect?
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+-. No.
Needs RNA polymerase |
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HIV is ___RNA. Does it infect?
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+. yes.
it carries reverse transcriptase. RNA-->ssDNA-->dsDNA-->rearrangement |
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How can we account for many people with HIV not getting AIDS?
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human endogenous retroviruses
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What 4 things are needed to synthesize RNA?
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1) RNA polymerase
2) promoters (TATA box) w/ sigma factor 3) enhancers 4) Rho-factor for termination |
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What does eukaryotic RNA polymerase need that prokaryotic doesn't?
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enhancers
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What's a common prokaryotic promoter sequence?
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TATA box
TTGACA |
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Which e.coli RNA polymerase subunit dissociates after transcription initiation?
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sigma factor
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Explain enhancer/UAS.
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upstream activating sequences
required for transcription upstream from promoters. tissue-specific |
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Name 3 methods of prokaryotic transcription termination.
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1) rho-factor
2) hairpin turns 3) intercalation by rifampicin |
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What's the difference b/t prokary. and eukary. mRNA's?
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both have 5' GTP cap
but eukary. have 3' polyA tail |
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How is eukary. mRNA synthesis terminated?
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polyA tail at 3' end
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Describe transcription of rRNA and tRNA in prok and eukary.
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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. |
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How does the mushroom poison work?
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it contains alpha-amanitin, which inhibits RNA polymerase II.
treated with aucubin |
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What's lupus (SLE)?
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autoimmune dz against SnRNPs
malar butterfly rash |
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What causes beta thalassemia? What selective advantage do they have?
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incorrectly spliced mRNA
malaria (RBC's do not have DNA; just proteins for carrying oxygen) |
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mRNA is more stabile in humans or e.coli?
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humans (10 hrs. vs. 5 minutes)
it's stabile RNA (like tRNA and rRNA) |
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Where do you splice mRNA?
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donor and acceptor splice sites
they have consensus sequences like "GU" and "AG" |
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___________ in _____________ catalyze the splicing of mRNA. How?
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SnRNP's in spliceosomes
-bind to 5' splice site -lariat formation (branched RNA) -5' cleavage, release, broken down -mature RNA remains |
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How can abnormal processing in the beta globin gene cause beta thalassemia?
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RNA mutations in INTRONS can cause mutations because of incorrect splice sites
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How do you get more than one protein from the same gene?
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alternate splicing
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all tRNA have ______ at 3' end.
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CCA
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Introns in mitochondrial genes are self-splicing, that is, they function as ___________.
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ribozymes
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polyA tails play a role in ?
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translation regulation
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Describe 3 regions of type II introns (mRNA) that are highly conserved/required for splicing.
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1) donor splice site at 5' end
2) acceptor splice site at 3' end 3) branch site at intron/exon boundaries AG:GU |
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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. |
