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96 Cards in this Set
- Front
- Back
DNA and RNA are polymers of what type of nucleotides?
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monomeric unit
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Each nucleotide is made up of what three components?
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1. a sugar
2. a phosphate 3. a base |
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What are the 4 bases found in DNA?
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A G C T
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What are the 4 bases found in RNA?
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A G C U
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How do DNA and RNA differ?
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at the 2' carbon
RNA has a hydroxyl group (ribose) DNA does not (deoxyribose) |
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Can RNA form double strands?
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yes, but it is generally found as a single stranded molecule in cells
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How are the two strands of a double helix DNA molecule oriented?
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wrapped around each other in an antiparellel orientation (one strand going 5' to 3' and the other going from 3' to 5')
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What are the two purines?
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A and G
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What are the three pyrimidines?
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T, U, and C
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What is base pairing in DNA?
In RNA? |
A-T C-G
A-U C-G |
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What can homologous regions of DNA be used for?
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they can be compaired among different species to determine phylogenetic relationships
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Closely related organisms contain similar DNA compliments, however.....
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they are often arranged differently on the chromosomes of each species
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What functions can RNA carry out?
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gene expression, catalytic activity, or signaling
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What are the 3 divisions, or domains the living world is made up of?
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bacteria, archea, and eukaryotes
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What are the 4 main processes for generating change in a genome?
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1. Intragenic mutation (single base change)
2. Gene duplication 3. DNA segment shuffling 4. Horizontal transfer (from one cell to another) |
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What is the difference between bacteria and eukaryotes with transcription and translation?
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coupled in bacteria
in eukaryotes: the two processes are separated by a nuclear membrane |
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What usually happens to bacterial genes?
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they are clustered into groups (operons) that are transcrived as a single unit
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How are eukaryotic genes often broken up?
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with regions of noncoding DNA (introns) between regions of coding DNA (exons)
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When comparing the same gene in several closely related species, what will you notice about the exons and introns?
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exons will generally be very similar (conserved)
introns will vary in size and content |
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How are bacterial chromosomes organized?
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densely packed with genes leaving very little DNA that is non-coding
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T/F Most of the DNA in higher eukaryotes including humans codes for proteins
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False, most does not code for proteins
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Most of the human genome is made up of what?
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repeated sequences
many are mobile and can move around in the genome |
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Bacterial chromosomes are _____ and eukaryotic chromosomes are ______
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circular
linear |
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Has the human genome been completed?
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Yes, along with a large number of other organisms
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Is it possible to construct a metabolic pathway?
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Yes, and you can compare them with other organisms by examining their entire genome content
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How can genes be grouped into families?
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based on similar (homologous) sequences found in different organisms
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Where can homologous sequences be found?
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in genes of the same organism that carry out different bu similar functions
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T/F Genes that have similar functions in very distantly related organisms can have similar sequences (homology).
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True
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What is used as a template to synthesize RNA during transcription?
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DNA
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What is RNA used for during translation?
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to code for protein molecules
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What is reverse transcription?
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when RNA is used as a template for DNA synthesis
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T/F Protein is used as a template to synthesize RNA or DNA
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FALSE!! protein is never used, but RNA and DNA can be used
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Each 3 nucleotides in an mRNA (codon) codes for what?
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one amino acid
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How many potential reding frames are there in each RNA molecule?
in double stranded DNA? |
3
6 |
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What are the 3 major types of RNA (based on their function)
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r RNA- structural component of the ribosome
mRNA- a copy of genetic information from a gene that is used during translation to specify (code for) a specific protein tRNA- transfer the 3 base coden on an mRNA into an amino acid on a ner polypeptide |
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When is tRNA used?
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during translation as a bridge between the mRNA and the synthesized protein
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How can phylogentic relationships of different organisms be compared?
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by comparing the DNA sequence of similar genes in the two organisms
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What is DNA polymerase?
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it's a DNA dependent (uses DNA as a template) DNA synthesizing enzyme
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What is RNA polymerase?
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it's a DNA dependent RNA synthesizing enzyme
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What is reverse transcriptase?
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an RNA dependent DNA synthesizing enzyme
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What is primase?
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a DNA dependent RNA polymerase
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What does primase do?
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synthesizes a small RNA "primer" that can be used by the DNA polymerase to elongate the chain
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What does DNA polymerase do?
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minimizes the number of mistakes by using a 3' to 5' exonuclease (or proofreading) activity that is part of the same protein
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Which direction will DNA polymerase synthesize?
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5' to 3' along with all other nucleic acid polymerases
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What happens during replication?
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each new nucleotide is added to the 3' carbon on the last nucleotide of the new DNA chain
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During what phase is DNA synthesized in eukaryotes?
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S phase
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The base component of each nucleotide is connected to the sugar at which carbon?
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the 1'
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The adjacent nucleotides in a DNA chain are attached at which carbons?
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5' and 3'
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Which carbon differs between RNA and DNA?
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2'
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What is DNA polymerase?
Can it initiate synthesis? |
it's an elongating enzyme
no |
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What is required for elongation of a new strand when using the DNA polymerase?
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a primer
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Bacterial chromosomes contain how many origins of replication?
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one
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How does DNA synthesis proceed in bacterial chromosomes?
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in both directions away from the origin until the two replication forks meet at a specific sequence on the other side of the chromosome
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Can new rounds of DNA replication begin before the previous round is completed in bacteria?
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yes
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How many origins of replication do eukaryotic chromosomes have?
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many that may change during the development of the organism
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Can new rounds of replication start before the previous round is completed in eukaryotes?
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no, new rounds do not start until after the cell divides
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What are special structures placed on each end of the chromosomes?
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telomers
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How are telomers constructed?
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with the enzyme telomerase that uses an RNA template to synthesize a short repeated DNA sequence at the ends of chromosomes
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Do the two polymerase molecules on opposite DNA strands move towards each other or away from each other?
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Opposite because they both go in the 5' to 3' direction
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What does helicase do?
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unwinds the 2 DNA strands before polymerization of the new strands
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What do single-stranded binding proteins do?
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keep the two complementary strands for reforming a double helix
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The polymerase on the leading strand moves toward what?
what about the polymerase on the lagging strand? |
Leading: replication ford
lagging: away from it |
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How is the lagging strand synthesized?
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in short (okizaki) fragments
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What does primase do?
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it initiates synthesis of each Okizaki fragment by making a short RNA primer
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How is the leading strand synthesized?
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the continuous movement of the DNA polymerase along the template
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What does the methylation of DNA signal?
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that the DNA is unreplicated and is ready to be used as a template for the next round of synthesis
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What are 4 things a PCR reaction requires?
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1. a set of primers
2. a target DNA sequence as a template 3. taq DNA polymerase 4. nucleotides |
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What happens for each cycle during a PCR reaction?
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the product of the previous cycle is used as a template for the next round of synthesis resulting in an exponential increase in the amount of DNA synthesized
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PCR is carried out in a _____
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thermocycler
it cycles through a series of temperatures |
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What is the Taq DNA polymerase used for in PCR?
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it's stable at high temps, allowing the DNA to be heat denatured, to separate the strands without destroying the enzyme
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How is PCR analyzed? Why?
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by gel electrophoresis because there is a large amount of the PCR product available after the PCR reaction
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what are the 4 events that can generate new or modified genes?
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1. point mutations in the coding region that change the amino acid composition of the protein
2. duplication of the entire gene 3. mixing of segments of one gene with segments of another gene- segment shuffling 4. transfer of genes between two organisms- horizontal gene transfer |
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T/F Many genes belong to gene families that share homologous regions. These regions usually code for proteins that carry out similar functions
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True
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Breaks in the DNA facilitate what?
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the initiation of recombination
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What can a defect in the DNA ligase cause?
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abmormal amounts of recombination
DNA ligase affects joining together of adjacent segments of DNA on a chromosome |
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Recombination
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the reciprocal exchange of genetic information
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Recombination can be the result of what 4 things?
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1. reciprocal exchange during cell division
2. DNA damage (x ray) 3. Introduction of foreign DNA 4. Programmed recombination during the development or maturation of a cell (ex: antibody producting genes during B-cell maturation) |
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What is gene conversion?
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the non-reciprocal exchange of genetic information
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Recombination between direct repeated sequences on the same chromosome causes what?
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the loss of DNA that was between the two repeated segments
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How can circular DNA be inserted in a chromosome?
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by recombination between a region of a circular molecule and a homologous region on the chromosome
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T/F Transposable elements are found only in bacteria
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False, they are found in all species from bateria to human
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What do transposable elements do?
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They can move from one location in DNA to another within that cell. They can cause changes in the DNA at the site of insertion
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Describe the 2 major types of transposable elements
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1. Contains inverted repeated sequences at the ends and causes a short region of the genome to be duplicated at the site of insertion
2. structuraly similar to a retrovirus and transposes through an RNA intermediate |
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What is unequal crossing over?
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recombination that resulted from imprecise pairing of tandemly repeated sequences
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What is the result of unequal crossing over?
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the loss or gain of gene copies
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What are the two type of mutations?
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1. DNA rearrangments
2. base substitutions |
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T/F There are many mechanisms in each cell for repairing DNA
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True
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What can happen from damage to a nucleotide?
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it can either be repaird or lead to a permanent mutation
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What are 2 things that can cause mutations?
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1. errors during replication
2. injury to the DNA from chemicals or radiation |
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What can be used to detect specific bacterial species in the oral cavity using PCR?
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species specific primers
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Can many of trhe bacteria detected by PCR be easily cultured?
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no
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T/F Many of the bacteria in the oral cavity are present in small amounts
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True
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A small fraction of every genome is made up of what?
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segmental duplications or large regions of DNA that are present in more than one copy
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how is the duplicated DNA is generated?
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gene amplification
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What can gene amplification result in?
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The resistance to drugs, transformation into cancerous cells, or other changes in cell phenotype
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Several human diseases are du to what?
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defects in DNA repair enzymes
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