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79 Cards in this Set
- Front
- Back
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DNA is ____% identical between individuals
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99.9
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Differences between DNA (aka mutations) can cause ____ effect or ____/
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1. little or no
2. disease or death |
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Define a mutation.
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any change in nucleotide sequence or DNA arrangement.
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Genome mutations create___
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aneuploidy
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Chromosome mutations do what?
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alter structure of individual chromosomes.
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Gene mutations do what?
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alter genes - can range from one to millions of nucleotides.
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What is a germ-line mutation?
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A mutation that occurs during gamete formation that is perpetuated to offspring.
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What is a somatic mutation?
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creates somatic mosaicism, but is not transferred to offspring.
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What are the types of gene mutations?
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basepair substitution, insertions, deletions.
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What are the two major mechanisms of mutation?
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1. DNA replication error
2. Problems with DNA repair |
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mis-segregation causes a ____ mutation and results in ___ or ___.
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1. genome mutation
2. monosomy or trisomy |
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Chromosome mutations are rarely passed to offspring because ____.
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They are normally incompatible with life.
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Describe somatic mosaicism.
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Different cells in the body may have different DNA in different cells. Ex - someone could have different DNA in bone marrow than rest of body.
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Mutations can be ___ or induced by ___/
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1. spontaneous
2. mutagens |
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What helps control the amount of mutations that persist during DNA replication?
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majority of errors are removed by repair enzymes that recognize the incorrect strand and fix it. If this didn't happen, mutation level would be deadly.
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How many nucleotides are damaged per day (before repair).
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10,000 to 100,000.
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What are the three basic types of nucleotide substitution mutations?
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missense, chain termination, and RNA processing mutations.
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What is a missense mutation?
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a point mutation alters the triplet (codon) and one amino acid is replaced with another.
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What is a chain termination mutation?
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a point mutation changes a normal codon to code for termination of translation. Results in unstable mRNA and shortened proteins.
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What results if a termination codon is altered?
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Codon may be changed to another amino acid codon and additional amino acids are tacked on resulting in regulatory problems in the 3' tail.
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What is an RNA processing mutation?
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a mutation at an intron/exon boundary that may interfere or abolish normal RNA splicing or creates new RNA splice sites.
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How many nucleotides are involved in an insertion or deletion?
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May be small number to large segment.
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What type of testing will help detect small deletions or insertions?
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Nucleotide sequencing
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What type of testing can detect large insertions/deletions?
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Southern blotting or PCR.
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What occurs if an insertion or deletion does not occur in a multiple of 3?
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A frame-shift mutation.
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What is a frame-shift mutation?
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A mutation that results in the interruption of a codon and messes up the reading of DNA.
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What are two examples of large deletions/insertions?
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Duchenne MD, alpha-thalassemias
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Which is more common, insertion or deletion?
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Deletions are more common
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What is a LINE sequence?
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Long Interspersed Nuclear Element - 1500+ BP segment that can be inserted anywhere thrughout the genome and move itself around including interrupting proteins, causing mutations, etc.
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What is one type of disease that results from LINE sequence insertion?
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an uncommon form of hemophilia A
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Recombination errors usually result from ____
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unequal crossing over
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What is a dynamic mutation?
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amplification of trinucleotide sequences - a codon gets repeated over and over, may be repeated once or many times.
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A dynamic mutation may expand, especially during ____
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gametogenesis
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If a gene is "fully penetrant" what does that mean?
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100% of people who express a given gene show all of the symptoms involved.
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What is required to measure germ-line mutation rates of a disease?
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Autosomal dominant disease that is fully-penetrant and identifiable at birth.
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What is the median rate for gene mutations?
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1x10^-6 mutations/locus/generation +/- 1000 mutations depending on location, etc (VERY LOW considering)
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Women are at greater risk of what type of error with age?
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non-disjunction in oocytes.
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Males are at greater risk of what type of error with age?
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replication errors in sperm
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True or False: all mutations are bad.
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False - some mutatons provide benefit or are neutral.
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Coding regions differ by ____ base pairs between individuals.
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1 out of 2500 base pairs.
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non-coding regions vary by _____ base pairs between individuals
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1 bp out of 1000 base pairs (more than coding).
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What is genetic polymorphism?
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allele variations found in >1% of the population (like hair color, eye color, etc)
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A rare variant is an allele found in ____ % of the population?
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less than 1%
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Single nucleotide polymorphisms usually have ____ alleles.
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Two
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What is the most common polymorphism?
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Single Nucleotide Polymorphism
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How many (estimated) variant positions are there in the human genome (where two individuals might differ)?
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about 10,000,000
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What are the two main types of insertion/deletion polymorphisms?
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microsatellites and minisatellites.
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What is an indel polymorphism?
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where we insert or delete between 2 and 100 nucleotides
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about 1/2 of the indel polymorphisms are ___ and 1/2 are ____ (variable numbers that are repeated in tandem)
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simple (only 2 alleles), multiallelic.
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What is a microsatellite?
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stretches of DNA with units of 2-4 nucleotides repeated many times.
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what is an STRP, where is it found?
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STRPs (short tandem repeat polymorphisms)...and are found among microsatellite polymorphisms... may repeat 1-100 times, each with different allele
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What is a minisatellite?
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tandem insertion of 10-100 nucleotide sequence. Typically result in many alleles.
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What are identified in order to do fingerprint analysis?
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STRPs between people to identify between them.
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What is a VNTR?
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Variable number Tandem repeats (within minisatellites).
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What is a CNP? What occurs with them?
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Copy Number Polymorphisms. variation in number of copies of larger genome segments (20-2million nucleotides
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One way of studying mutation other than DNA is ___
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Studying the protein product that results and variation among it.
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What percentage of proteins are slightly different among individuals?
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around 20%
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THe way one protein interacts with another, when considering small differences in the proteins creates ______ among individuals.
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Chemical uniqueness.
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What is two of the biggest examples of protein polymorphisms.
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ABO blood groups and MHC receptors
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ABO blood type is based on how many alleles? It is determined by a locus on which chromosome?
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3 - a protein, b protein, or o protein
Chromosome 9 |
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Blood type A = anti ___ antibody
blood type B = anti ___. blood type AB = anti ____ blood type O = anti ____ |
B
A none A and B |
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The blood type alleles alter the ____ antigen on the surface of a RBC.
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H antigen
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Type A blood has the ___ antigen that alters the H antigen.
Type B has the -____ .... Type O has the ____... Type AB has the ___.. |
A antigen
B antigen no antigens - just the normal unaltered H antigen both A and B antigens. |
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The Rh polypeptide is encoded by a gene on chromosome ____/.
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1
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The A and B blood types are due to a ____, and the O blood type is due to a ____ that results in a ___.
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4-base substitution,
deletion that results in a frame-shift mutation. |
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What gene codes for the Rh polypeptide?
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RDH gene on chromosome 1
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What is an MHC? What does it do?
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Major histocompatibility complex. Helps cell identify self as self.
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How many classes of the MHC genes are there?
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3 (I, II, III)
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What chromosome carries the gene cluster for MHC?
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short arm of chromosome 6
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How many alleles are present for HLA (human leukocyte antigens) class I and II?
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Many hundreds of alleles are known.
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What types of cells have MHC class I antigens?
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all nucleated cells (not RBCs) (present endogenous material)
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What types of cells have MHC class II antigens?
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B-cells and APCs. (present exogenous material)
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Which classes of MHC genes correspond to HLA?
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Classes I and II.
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What do MHC class I genes do (HLA-A, B, C)?
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code for proteins that create the plasma membrane to present the material to CD8+ (cytotoxic) T cells.
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What do MHC class II genes do (HLA-DP, DQ, DR)?
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code for proteins that present exogenous antigens to CD4+ T-cells
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Anklysoing spondylitis is the result of a mutation of ____
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HLA proteins
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When it comes to organ transplantation, only ____ allows for no immunosuppressive therapy.
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perfect match of every single HLA and blood group alleles (only possible with identical twin)
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What is GVHD?
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___ in which a graft can reject its new host.
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What is the greatest transplant challenge? Why?
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Bone marrow - if even 1 HLA is mismatched, you have essentially replaced the immune system with an immune system that recognizes the entire body as foreign and attacks the host from inside out.
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