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64 Cards in this Set
- Front
- Back
Nucleosomes coiled around each other forms what?
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solenoid
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In interphase, DNA is coiled to what extent? (What structure is the highest level of organization in interphase)
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solenoid
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The solenoid structure condenses DNA how much from the beads-on-a-string state?
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50-fold more condensed
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One coil of a solenoid consists of what?
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5-6 nucleosomes coiled together
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During mitosis and meiosis, the DNA is condensed how much from its original state?
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5000:1
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What protein closes DNA nicks as they form in the coiling process?
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topoisomerase II
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Topoisomerase II binds to what regions of DNA?
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AT-rich
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What 2 bands form in Giemsa staining?
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dark=G bands, AT rich, less transcriptionally active
light=R bands, GC rick, more active |
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ribose backbone has what kind of linkage?
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phosphodiester
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Key difference btwn DNA and RNA at molecular level
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DNA has H at 2' position, RNA has an OH
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How many hydrogen bonds form btwn C-G pairing?
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3 hydrogen bonds
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What type of bonds form when base pairs link between strands?
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hydrogen bonds
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How many hydrogen bonds form btwn A and T bases?
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2 hydrogen bonds
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Length between base pairs in a DNA strand
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0.34 nanometers
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What is a ddNTP and how is it different fom a dNTP?
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di-deoxy nucleotide triphosphate--missing the 3' OH, so nothing can be added to the chain
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How many base pairs in human genome?
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3 billion (3 x 10 9)
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How many base pairs in a megabase?
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1,000,000
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How long is 3.4 Angstroms? (distance btwn base pairs)
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0.34 nanometers
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Where is the base actually attached to the ribose backbone?
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The base (G,A,T, orC) is attached to the 1' carbon of the ribose backbone.
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Type of bond that links bases within the same DNA chain.
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phosphodiester linkage
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Chargaff's rule
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A pairs with T
G pairs with C |
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What are the purines? pyrimidines?
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purines = adenine, guanine
pyrimidines=cytosine, thymine (y in name) and uracil |
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Difference in purines and pyrimidines
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Purines are bigger and have 2 rings. Pyrimidines have only 1 ring.
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Describe that part of the centromere where the kinetochore microtubules bind
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171 bp repeat called alpha-satellite DNA. AT-rich. Kinetochore proteins bind here.
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What telomere sequence is conserved across all chromosomes, and even across species?
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GGGTTA
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Names of the 2 strands on newly-replicated DNA
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leading and lagging strands
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Name of pieces of lagging strand DNA that must be joined together
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Okizaki fragments
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What does helicase do?
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unwinds DNA and breaks hydrogen bonds prior to replication
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What enzyme stimulates DNA polymerase activity during replication?
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proliferating cell nuclear antigen
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What enzyme removes RNA from an RNA-DNA hybrid?
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Ribonuclease H1 (RNAse H1)
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DNA ligase connects what?
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3' hydroxyl to 5' phosphate group
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What enzyme relaxes DNA by breaking and resealing phosphodiester bonds?
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topoisomerase
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What happens at the 2nd cell cycle control point, at the G1/S border?
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site of p27 inhibition of cdk2-cyclin E
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What happens at the 3rd cell cycle control point, at the G2/M border?
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activation of cdc2-cyclin B
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What happens at the 4th cell cycle control point, at the end of mitosis?
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degradation of cyclin B
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Lagging strand primers are made of what?
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RNA
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When the strands are separeated for DNA replication, what keeps them apart?
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single-stranded DNA binding protein (replication protein A)
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Which polymerase works on the leading strand, and which on the lagging strand?
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leading =DNA polymerase delta
lagging = DNA polymerase alpha + DNA primase subunit |
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When a deoxynucleotide triphosphate is added to the 3' end of the growing strand, how many phosphates are lost?
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2
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Name 3 syndromes caused by helicase malfunction.
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WRN helicase=Werner
RECQ4=Rothmund-Thompson syn. BML helicase=Bloom |
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Characteristics of Bloom syndrome
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IUGR
hypo/hyper pigmentation butterfly telangiectasia microcephaly, high-pitched voice normal IQ immunodificiency azospermia premature ovarian failure increased risk for cancer |
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Describe what happens at telomeres during replication?
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Telomerase binds and has an RNA template seq. that matches the telomere repeat. Shifts down repeatedly to add new 6 bp sequence.
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Name some types of splice site mutations
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cryptic splice sites (uncover old or create new)
ESE (exonic splice enhancer)-may be a silent AA change donor/acceptor/branch site |
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Sequence at the exon/intron donor site
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GU
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Sequence at the intron/exon acceptor site
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AG
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Freq. of Tay-Sachs among AJs
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1/3000 AJs
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Freq. of PKU
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1/12,000
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Enzyme missing in SCIDs
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Adenosine deaminase
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3 common Tay-Sachs mutations
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4bp insertion into exon 11
Splicing mutation in intron 12 Gly-to-Ser missense in exon 7 |
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4 common Gaucher mutations
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L444P missense in exon 10
IVS2+1 84GG (frameshift) N370S missense in exon 9 |
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Common PKU mutations
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IVS12nt1
R158Q R261Q R408W |
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Many common mutations for common diseases are diagnosed by what 2 techniques?
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PCR, ASOH (allele-specific oligo hybridization)
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Name some example of how dominant haploinsufficient conditions can be highly dependent on environmental factors?
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acute intermittent porphyria (heme biosynthetic pathway), familial hypercholesterolemia
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What are porphyrins? What is acute intermittent porphyria?
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Intermediate in heme biosynthesis. Anemic episodes occur due to environmental factors, need to turn up heme pathway top make more. There is a rate-limiting enzyme, porphyrins build up in blood, cause pain, photophobia, psychosis (vampire-like)
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Defective protein in familial hypercholesterolemia? Mode of inheritance?
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Low-density lipoprotein
Dominant (haploinsufficient) |
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Freq. of familial hypercholesterolemia
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1/500
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Freq. of Huntington
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1/10,000
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Protein altered in myotonic dystrophy? Frequency?
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protein kinase
1/10,000 |
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Freq. of OI
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1/10,000
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What is highly parallel genotyping?
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Looking at many different SNPs or loci at once. Includes microarray, SNP array. Note that CGH doesn't really look at genotype, but just copy number.
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Name one condition in which Southern blooting is still used for diagnosis. Why?
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Fragile X--PCR is ineffective at long repeat expansions.
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What is an STS?
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Sequence tagged site. Unique spot in genome amplified by PCR. STS content mapping--used to find the order of sites on YAC clones, for physical mapping=a contig.
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How many base pairs are btwn 2 loci with a 1% recombination rate?
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1% recombination rate=1 centimorgan =1 million base pairs
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With regard to SNPs, what is a haplotype? How many haplotypes exist within a particular population at a locus?
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A haplotype is a group of SNP inherited as a unit. Typically 2-10 haplotypes in a population.
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