Term
• Describe the types of lesions each DNA repair pathway corrects. |
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Definition
-Direct Repair= thymine dimers; alkylation by EMS
-Base Excision Repair= non-helix distorting changes of individual bases
-Nucleotide Excision Repair= bulky, helix distorting lesions
-Mismatch Repair= corrects mismatches not caught by proofreading during replication
-Homologous Recombination= uses sister chromatids synthesized for replication to fix double-stranded breaks
-Non-Homologous Recombination= fixes double stranded breaks without aid of sister chromatids |
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Term
For direct repair, explain the function of DNA photolyase and alkyltransferase. |
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Definition
-Photolyase= recognizes thymine dimers and splits them
-Alkyltransferase= removes methyl and ethyl groups from guanine |
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Term
• Explain how N-glycosylase and AP endonuclease function in base excision repair. |
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Definition
-N-glycosylase= cleaves base from sugar
-AP Endonuclease= makes a nick on the 5’ backbone |
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Term
• Describe the three different ways the sequence of DNA can be restored in base excision repair. |
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Definition
3) DNA Poly S or E synthesizes short segment DNA by created a flap |
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Term
• Explain the actions of UvrA, UvrB, UvrC, UvrD, DNA polymerase, and DNA ligase in nucleotide excision repair. |
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Definition
-UvrA/UvrB= finds damaged DNA; UvrA hten dissociates
-UvrC= attaches to site left by UrvA and makes a cut on both sides of damaged site
-UvrD= removes damaged DNA (UvrB/C released)
-DNA polymerase= fills in the gap, using undamaged strand as a template
-DNA Ligase= glues the new connection together |
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Term
Describe how DNA methylation directs mismatch repair through the actions of MutH, MutS, and MutU. |
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Definition
-MutS= locates mismatch
-MutH=distinguished between parental and daughter strand and binds to site with methylation and then cuts the methylated strand
-MutU= separates the strands
-DNA POLY and LIGASE fill in the gaps and seal it back together |
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Term
• Compare and contrast homologous recombination repair and non-homologous end joining. |
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Definition
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Non-Homologous
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Same
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Homologous
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-Can Occur at any stage of cell cycle
-Doesn’t involve sister chromatids
-May lose some genetic info
-Blunt cuts (no overhangs)
-recruits proteins
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-Double stranded breaks
-DNA repair pathway
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-Can only occur around the time of replication
-Involves use of sister chromatids
-Strand exchange occurs
-Single strand overhands
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Term
• In the Holliday model of recombination, describe the formation of a Holliday junction and how this leads to heteroduplex regions. |
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Definition
-Holiday Junction= a site where an unresolved crossover has occurred between two homologous chromosomes; creates two separate chromosomes
Because the DNA sequences in the homologous chromosomes are similar but may not be identical, the swapping of the DNA strands during branch migration may produce a heteroduplex (a region in the double stranded DNA that contains base mismatch) |
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Term
Explain which strands are then broken to give non-recombinant chromosomes OR recombinant chromosomes |
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Definition
IF breakage occurs in the strands that were not originally nicked, the rejoining process results in recombinant chromosomes |
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Term
• In the double-strand break model of recombination, describe how D-loop formation and gap repair synthesis lead to heteroduplex regions. |
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Definition
After D-loop is formed, two regions have a gap in the DNA. DNA synthesis occurs called DNA gap repair synthesis. Once this is completed, two Holliday Junctions are produced, either recombinant or non-recombinant, which contain small heteroduplexes (base mismatches) |
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Term
• Explain how gene conversion can occur during recombination. |
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Definition
Gene Conversion occurs when recombinant chromosomes are repaired and result in two copies of the same allele
Mismatch Repair of a Heteroduplex Region; the two chromosomes had different alleles due to a single base pair difference in DNA sequences
DNA Gap Repair Synthesis; double stranded breaks |
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Term
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Definition
| = two copies of a gene segregate from each other during transmission from parent to offspring |
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Term
| Law of Independent Assortment |
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Definition
| two different genes will randomly assort their alleles during the formation of haploid cells. |
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Term
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Definition
| general characteristics Ex: eye color |
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Term
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Definition
| specific properties of character Ex: blue eyes |
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Term
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Definition
| determines “goodness of fit” between observed and expected data |
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Term
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Definition
| = states that there is no real difference between the expected and observed value, and any difference is attributed to random sampling error |
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Term
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Definition
| deviation between the observed and expected outcomes due to chance |
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Term
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Definition
| n-1) where n= # of categories independent of each other |
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Term
| • Describe the different phases of the eukaryotic cell cycle, including phases of mitosis. |
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Definition
G1 Phase= cells prepare to divide
S phase= chromosomes are replicated; two copies are called chromatids join at centromere to form sister chromatids
G2 Phase= cell accumulates materials necessary for nuclear and cell division
Prophase= nuclear membrane dissolves and nucleolus becomes less visible; chromatids condense; mitotic spindle begins to form
Prometaphase= nuclear membrane is completely gone; spindle fibers begin to interact with sister chromatids; mitotic spindle is completely formed
Metaphase= sister chromatids align on metaphase plate
Anaphase= centromere breaks; chromosomes move toward the pole to which they are attached
Telophase= chromosomes reach poles and un-condense; nuclear membrane reforms |
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Term
| • Compare and contrast mitosis and meiosis. |
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Definition
Mitosis Similarities Meiosis
-somatic cells
-2 daughter cells
-1 division
-diploid
-genetically identical Involves PMAT
Cellular division -germ cells
-4 daughter cells
-2 divisions
-haploid
-crossing over occurs |
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