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19 Cards in this Set
- Front
- Back
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What were the goals of the Human Genome Project?
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Identify all genes in human DNA and determine their base pair sequences
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What are the three categories of DNA in the human genome? Roughly what percentage of the genome does each comprise?
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Single Copy DNA: >50%
Repetitive DNA: 25-50% Mitochondrial DNA: non-nuclear circular DNA (no percentage given) |
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What functions does Single Copy DNA serve?
What are its characteristics? |
Codes for proteins; introns, "pseudogenes" (don't form proteins)
Sequence represented only once or at most a few times in genome |
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What functions does Repetitive DNA serve?
What are its characteristics? |
Maintains chromosome structure; source of variation between individuals
Distribution throughout genome is UNEVEN |
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What are the two subtypes of Repetitive DNA? What are their subtypes? Describe their roles.
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Dispersed repetitive DNA: related sequences scattered across genome
Subtypes: LINES (Long Interspersed Nuclear Elements), Alu family Satellite DNA: clusters of tandem repeats of short DNA sequences Subtypes: alpha-satellite: contribute to proper centromere functioning; chromosome specific minisatellite: highly polymorphic among individuals; used in forensic and paternity testing microsatellite: SHORT TANDEM REPEATS; most commin CA repeat; also polymorphic among individuals, can be used in forensic testing |
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What is the definition of a mutation?
What are the three categories of mutations? Describe them and give examples. |
Mutation: change in nucleotide sequence or arrangement of DNA
1) Genome mutations: affect number of chromosomes; due to MISSEGREGATION during meiosis (Trisomies 13, 18, 21; Turner Syndrome; Klinefelter Syndrome) 2) Chromosome mutations: alter structure of individual chromosome; Ex: Translocations, Deletions, Duplications, Inversions 3) Gene Mutations: alter individual genes; due to errors in DNA replication OR failure to correctly repair DNA damage (no examples) |
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What is a point mutation?
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Nucleotide Substitution
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What is a Silent Mutation? Where are they likely to occur (on DNA)?
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substitution of nucleotide for another that doesn't alter amino acid sequence or functional protein
Can occur in SILENT REGIONS of genome (in INTRONS) |
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What is a Missense Mutation? Examples?
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Nucleotide substitution that laters amino acid coded
Ex: hemoglobinopathies (Sickle Cell) |
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What is a Nonsense Mutation?
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Point mutation in DNA sequence that results in termination codon (UAG, UAA, UGA); translation stops prematurely, creating truncated and non-functional protein
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Provide two examples of mutations that occur in non-coding regions of DNA.
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Regulatory element mutations: affect binding of RNA polymerase to promoter, also affects transcriptional activators/inactivators; results in altered production of mRNA and protein
RNA processing mutations: creates/destroys signals for splice sites between exons and introns; leads to improperly processed mRNAs |
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Nucleotide Transition vs Nucleotide Transversion
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Transition: Substitution of one purine for another purine or one pyrimidine for another pyrimidine (PUR AG, PYR CUT)
Transversion: swap purine for a pyrimidine or pyrimidine for a purine |
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Why are transitions overrepresented among point mutations?
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Methylation of cytosine residues; spontaneous deamination in CG doublet
CG doublet = HOTSPOT for mutation |
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What is achondroplasia? How does it arise?
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achondroplasia: short limb dwarfism
Arises from hotspot mutation in Fibroblast Growth Factor Receptor 3 Gene |
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How does a frameshift mutation occur?
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Number of bases involved in insertion/deletion is not a multiple of three
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What is a Tandem Repeat Expansion? Give an example of a disease it causes.
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Addition of three repeated nucleotides adds extra copies of an amino acid into the protein, interfering with normal folding
Ex: Fragile X Syndrome (Huntington's, Friedrich's, Myotonic Dystrophy) |
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Is most DNA considered junk DNA?
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Sort of, most DNA consist of repeat sequences which interact with surrounding sequences and nearby genes. More like a genomic scrap yard.
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What is a SNP?
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Single Nucleotide Polymoprhism: DNA sequence variation that occurs when single nucleotide differs between members of a species; represents a natural genetic variability
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Do SNPs cause disease? What are their uses?
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no, SNPs do not cause disease, but can serve as biological markers and can make associations with favorable/unfavorable drug treatments/interactions (personalized medicine).
SNPs can be used to create a genetic signature profile; each individual's genome contains a unique SNP pattern. |
