ch 15 Genetics terms

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amberd27
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ch 15 Genetics terms
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2011-12-12 03:57:23
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BIOL 350 genetics term identification
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  1. Barbara McClintock
    maize cytogeneticist that discovered transposable elements
  2. Ds trnasposable element
    Ds for dissocation. Helps cause breakage of the chromosome. Considered nonautonomous element, meaning they require other elements for mobility
  3. Ac transposable element
    Ac for Activator, as it activates the breakage of chromosome 9 at the Ds locus. Autonomous element as it requires no other elements for mobility
  4. In Maize coloring, when Irreversible c paired with:
    a) C gene (wild type)
    b) c-m (Ds) (no Ac)
    c) c-m (Ds) (+Ac)
    d) c-m(Ac)
    • a) pigmented
    • b) colorless
    • c) spotted kernels
    • d) spotted kernels
  5. transposase
    enzyme required for the movvement of IS elements from one site in the chromosome to another. Binds the ends of Ac and Ds elements
  6. IS (insertion-sequence) elements
    Segments of bacterial DNA that can move from one position on a chromosome to a different position on the same chromosome or on a different chromosome. When they appear in the middle of genes, they interrupt the coding sequence and inactivate the expression of that gene.
  7. Composite transposons
    One of two types of bacterial tansposons/ Contain a variety of genese that reside between two nearly identical IS elemnts that are oriented in opposite direction, and thus form IR (inverted repeat) sequence.
  8. Simple transposons
    One of two types of bacterial tansposons which are flanked by IR sequences, but these sequences are short and do not encode the transposase enzyme necessary for transposition. Encode their own transposase in addition to carrying bacterial genes.
  9. cointegrate
    Fused circle created in replicative transposition; the donor and target plasmid temporarily fuse together to form a double plasmid, which gets cut at the two ends of Tn3 and the target sequence, whose free ends are fused together to create the cointegrate circle. It is then turned into two smaller circles, leaving one copy of the transposable element in each plasmid
  10. replicative transposition
    A new copy of the transposable element is generated in the transposition event, with one copy at the new site and one copy at the old site.
  11. conservative transposition
    No replication; instead the elemnt is excised from the chromosome or plasmid and is integrated into the new site. AKA "cut and paste"
  12. R factors
    plasmids carrying genes that encode resistance to several antibiotics
  13. retrotransposons
    Transposable elements that employ reverse transcriptase to transpose through an RNA intermediate. Ex is Ty elements in yeast, copia elements in Drosophila
  14. retrovirus
    single stranded RNA virus that employs a double stranded DNA intermediate for replication. The RNA is copied into DNA by the enzyme reverse transcriptase.
  15. LINEs
    long interspersed elements; move like a retrotransposon with the help of an element encoded reverse transcriptase but lack some structural features of retrovirus like elements, including LTRs.
  16. SINEs
    short interspersed elementes; no reverse transcriptase. Best described as nonautonomous LINEs, because same structure, but no reverse transcriptase encoded. The most abundant SINE in humans is Alu, which makes up over 10% of human genome
  17. safe havens
    region of the genome where there are few genes; a successful transposable element increases copy number without harming its host, and one way in which an element safely increases copy number is to target new insertions into these safe havens
  18. P element in Drosophila
    Transposable elemnte that was discovered as the cause of hybrid dysgenesis, a phenomenon that occurs when females from lab strains of D. melanogaster are mated with males derived from natural populations. Used in the lab to tag genes for cloning, or as a vector to introduce genes
  19. Reverse transcriptase is needed for transposition of
    retrotransposons
  20. _____ contain genes such as antibitoic resistance in addition to the genese needed for transposition
    composite transposons
  21. Describe possible consequences on gene expression when: a LINE inserts into an enhancer of a human gene
    In the simplest scenario, the inersetion prevents the binding of transcriptional activators that are reqd for the ultimate binding of RNA poly to the promoter. Thus, the gene will not be expressed, as no mRNA will be synthesized
  22. Describe possible consequences on gene expression when: a transposable elemente contains a binding site for a transcriptional repressor and inserts adjacent to a promoter
    The presence of the transposable element will provide a binding site for the transcriptional repressor to bind near the promoter and prevent the binding of RNA poly II
  23. Describe possible consequences on gene expression when: an Alu element inserts into the 3' splice (AG) site of an intron
    the Alu element will be transcribed into RNA with the rest of the gene sequences and will prevent the splicing of the intron that is has inserted into. The insertion will almost certainly result in a null allele as the Alu sequence and the intron will now be translated. The intro, Alu, or both will probably contain stop codons.
  24. Describe possible consequences on gene expression when: a Ds element that was inserted into the exon of a gene excises imperfectly and leaves 3 base pairs behind in the exon
    The insertion and excision will result in a 3 bp indel in the exon and slighlty alter the amino acid sequence of the protein, but it won't produce frameshift mutation. The minor change in the amino acid sequence may or may not affect the function of the encoded protein
  25. Describe possible consequences on gene expression when: an excision by the Ds element leaves 2 base pairs behind in the exon
    This insertion and excision will cause a frameshift mutation and is more likely to impair protein function
  26. Describe possible consequences on gene expression when: a Ds element that was inserted into the middle of an intron excises imperfectly and leaves 5 base pairs behind in the intron
    Will likely not affect gene expression an the intron will probably still be spliced correctly

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