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Lecture 2

BIOB11H3 Lecture Notes - Lecture 2: Transposable Element, Gene Duplication, Genome Evolution


Department
Biological Sciences
Course Code
BIOB11H3
Professor
Dan Riggs
Lecture
2

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OP2: Genome evolution and polymorphisms
Smart Pages: Figs 10-19, 20, 23, 24, 26, 27, 30, SNP figure from Quercus
Vocabulary Words: transposition/transposon/retrotransposon/reverse transcriptase/
/polymorphism/RFLP/SNP/deletion/duplication/haplotype/unequal crossing over/gene
family/in situ hybridization/trinucleotide repeat
Central ideas:
1. Transposable elements are mobile elements of the genome, sometimes disrupting
gene function and generating new phenotypes.
2. Transposable elements are usually flanked by both inverted and direct repeats, and
generate direct repeats upon insertion.
3. Autonomous elements encode one or more enzymes involved in their movement
(transposase).
4. Transposition can occur by two general mechanisms: non-replicative and replicative
involving an RNA intermediate.
5. Mutations may involve changes to single nucleotides, duplications and deletions of
DNA, chromsomal inversions, and insertion of foreign DNA.
6. Polymorphisms are useful in forensics, paternity suits, and may be useful in the
development of pharmaceuticals and therapies.
Questions a scientist might ask:
1. How do transposable elements move?
2. What are the consequences of non-replicative transposition?
3. What are gene families?
4. Do individual members of gene families encode proteins with different functions
and are they expressed differentially? Why?
5. How are DNA polymorphisms useful for determining the guilt/innocence of a crime
suspect?
Sample multiple-choice question:
Following gene duplication, what are the possible things that can happen to the duplicated
gene?
a. The duplicated gene can accumulate favorable mutations and acquire a new
function.
b. The duplicated gene can be lost during evolution through deletion.
c. The duplicated gene can be rendered nonfunctional by unfavorable mutations.
d. If there are two copies of the gene, both could undergo mutation so that each
evolves a more specialized function than the original gene.
e. All of these are correct.
Analytic/review questions: See questions 1,2 on page 394; also questions 7, 9, 15, page
403.
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