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55 Cards in this Set
- Front
- Back
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Replicative transposons and non-replicative transposons differ in what?
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Forming the conintegrates during transposition
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The e.coli mismatch repair system can identify the strands containing incorrectly inserted nucleotides by what?
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Recognizing the methylation state of the adenine in the GATC sequences.
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During prokaryotic translation initiation, the small subunit of the ribosoe first binds to what?
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The shine-dalgarno sequence
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What is a mutation changing an adenine to a cytosine?
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A transversion mutation
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Deamination of the cytosines in DNA will most likely be repaired by?
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base excision repair
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The transmission of spongiform encephalopathy by prion is sensitive to what type of nuclease?
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protease
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The phenomenon of semisterility is caused by?
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The adjacent segregation of reciprocal translocations
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Which of the following is not found in DNA?
a. purines b. phosphates c. ribose d. deoxyribose e. thymine |
c. ribose
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Which of the following describes the packaging of nucleosomes into solenoid?
a. 11nm fiber b. 30 nm fiber c. 300 nm fiber d. 700 nm fiber e. chromatids |
b. 30 nm fiber
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A 300 base pairs circular DNA with 34 helical turns is likely to form?
a. negative supercoils b. a relaxed circular molecule c. positive supercoils d. 11 nm fiber e. hairpin loops |
c. positive supercoils
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What enzyme would be responsible for the mutation of the following in ecoli:
Newly synthesized DNA contains many mismatched base pairs |
3'-5' exonuclease of DNA polymerase
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What enzyme would be responsible for the mutation of the following in ecoli:
Okazaki fragments accumulate, and DNA synthesis is never completed |
DNA polymerase I
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What enzyme would be responsible for the mutation of the following in ecoli:
No initiation occurs |
dnaA, which binds tot he replication origin and facilitates replication initiation
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What enzyme would be responsible for the mutation of the following in ecoli:
Supercoiled strands are found to remain following replication which is never completed |
gyrase
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When chromatin is treated wwith a moderate salt concentration, the linker histone H1 is removed. Higher salt concentration removes the rest of the histone proteins. If the nuclease digestion were carried out after the DNA was treated with moderate of high salt, what would the expected results be?
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With moderate salt, H1 histone but not the other histones is removed. Nuclease digestion of DNA treated with moderated salt should then yield DNA size protected by the nucleosome core particle. With high salt, all histones are removed. Nuclease digestion of naked DNA should yield a smear by no discrete bands.
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RNA molecules have three phosphates at eh 5' end, but DNA molecules never do. Explain
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RNA polymerase can initiate synthesis without primers. DNA polymerase cannot.
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A geneticist discovers that two different proteins are encoded by the same gene. One protein has 56 amino acids, and the other has 82 amino acids. Provide a possible explanation for how the same gene can encode both of these proteins.
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Alternative splicing
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
ori site |
Replication
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
3' slice-site consensus |
RNA processing
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
poly (A) tail |
RNA processing
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
terminator |
Transcription
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
start codon |
Translation
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
-10 consenses |
Transcription
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What process out of replication, transcription, RNA processing, or translation would most be affected by the deletion of the following:
Shine-Dalgarno |
Translation
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In many eukaryotic organisms, a significant proportion of cytosine bases are natuarally methylated to a 5-methylcytosine. Through evolutionary time, the proportion of AT base pairs in the DNA of these organisms increases. Suggest a mechanism
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When 5-CH3-cytosine spontaneously deaminates, it becomes thymines, and pairs with T. This causes CG to TA transitions. Unlike the deamination of cytosine to uracil, the deamination of 4-CH-cytosine to Thymine does not cause a change that can be recognized by a glycosylase (since T is a normal base in DNA.) So this mutation is not repaired, and over time AT base pairs accumulate where once were GC.
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Acridine orange is an effective mutagen for producing null alleles by mutation. Why?
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Acridine is an intercalating agent, which causes frameshifts, which lead to nonsense codons (=null alleles)
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A certain acridine-like compound gereates only single insertions. A mutation induced with this compound is treated with the same compound, and some revertants are produced. HOW?
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These must be second site revertants. We discussed in class that a frameshift mutation can be repaired by a suppressor tRNA with a 4-base anticodon. So the second insertion could be in a tRNA gene.
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If DNA polymerase makes amistake in copying a template strand, there are two chances to fix it before it becomes a permanent mutation. What are these two chances?
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Proofreading (3'to 5' exonuclease) activity of the DNA polymerase and mismatch repair, with the Mut proteins, as long as the newly synthesized DNA has not yet become methylated
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Increasing the amount of transcription for the dam gene considerbly increases the mutation rate in most cells. why?
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the more dam protein in the cells, the faster teh adenin methylation at GATC sequences occurs. Once methylation has happened, mutations have become permanent in the genome. So, the shorter the time between replication and GATC methylation, the fewer mismatches get fixed, and the higher th mutation rate.
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After an experiment in which E.coli wre placed under a UV lamp to cause mutations, the bacteria were placed in the dark. Why?
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UV mutations cause pyrimidine dimers, which can be repaired in E.coli by photolyase. Photolyase uses blue light for the repair energy, so keeping mutations in the dark helps prevent their being repaired.
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Whould any UV- induced mutations be repaired in the dark?
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Sure. Both the nucleotide excision repair and the SOS systems work fine in the dark. The systems also are used in ecoli to repair the pyrimidine dimer.
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Ecoli lexA null mutants can only divide for a few generations before they die out, so the lexA mutation is considered lethal. Explain
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Without the LexA repressor, UmuD and C are constituitively transcribed and translated. UmuDC added to PolIII makes PolV. While PolV is needed for SOS repair, it also causes mutation by carrying out untemplated DNA synthesis. After a few generations of this, enough mutations accumulate in the cell to be lethal.
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Pericentric inversion
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The centromere is included in the inverted segment
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Paracentric inversion
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the centromere is not part of the rearranged segment
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What are the genetic consequences of recombination within a paracentric inversion?
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1. An inversion loop forms
2. crossing over within loop 3. the two chromosomes are connected together (bridged |
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What are the genetic consequences of recombination within a percentric inversion?
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1. An inversion loop forms
2. crossing over with the loop. 3. Centromeres do not line up in resulting chromosomes 4. The recombinant games that are produced are nonviable because genes are missing or present in too many copies |
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What are the three properties of inversions?
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1. Inversion homozygotes are normal. Just diff gene order.
2. products of meiotic recombination within an inversion do not contribute 3. Thus genes of a chromosome with an inversion appear to be tightly linked |
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What are the three ways to detect an inversion?
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1. cytologically - band order and presence of loops, bridge during anaphase
2. genetics - gene map order will be altered 3. physically |
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What is a balancer chromosome?
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1.has recessive lethal mutation
2. has inversions, lots 3. carries a dominant marker to help identification. |
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What is a translocation mutation?
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The movement of achromosomal segment to a new loctaion in the genome.
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What is a nonreciprocal translocation?
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genetic material moves from one chromosome to another without any reciprocal exchange.
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What is a reciprocal translocation?
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Involves the exchange of seegments between to nonhomologous chromosomes.
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What does adjacent segregation of reciprocal translocations cause?
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Semi-sterility
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What is a Robertsonian translocation?
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Involves breaks at the extreme ends of the short arms of two nonhomologous acrocentric chromosomes.
The small acentric fragments are lost the the larger chromosomal segments fuse at their centromeric region, producing a new larger submetacentric or metacentric chromocome. These are the most common types of chromosome rearrangement in humans. Familial Down |
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How is Chronic Myelogenous Leukemia happen?
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Reciprocal translocation between long are of chromosome 22 and the tip of the long are of chromosome 9.
This translocation produces BCR-ABL, which is more active than the normal ABL gene. The fusion protein stimulates increased, unregulated cell division, eventually leads to leukemia. |
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Centromeres ensure what during mitosis and meiosis?
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Proper segregation of genes
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What molecules are not linked to chromosomes and behave differently during mitosis. Also they do not obey mendels rules.
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Organelle Chromosomes
DNA and RNA plasmids Protein structure |
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What does genome of mitochondria encode for?
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2 rRNAs, 22 tRNA's for protein sythesis
13 proteins for energy metabolism |
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Mitochondrial proteins are encoded 99.9% by what?
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nuclear genes
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Nuclear DNA
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linear
3 x 10^6 kbp >30,000 genes Contains two copies of each gene encodes all cellular functions, including mitochondrial |
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Features of mitochondrial DNA
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17kbp
circular 37 genes cell contains 1000s of copies Encodes only mitochondral functions |
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What is some evidence for the endosymbiont theory?
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1.similar lipid compositions in membranes of bacteria and mitochondria
2. bacterial and mitochondrial genomes cicular and lach associated histones 3. protein synthesis in bacteria and mitochondra similar 4. rRNAs similar in bacteria and mitochondria |
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What are the two general patterns of mitochondrial inheritance?
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1. maternal
2. all mitochondria within an individual are genetically identical |
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Homoplasmy
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The existence of a uniform population of organelles within a cell or an individual
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Heteroplasmy
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A geterogeneity of organelles within a cell or an individual.
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