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TLS Online TPP Program

#Question id: 2768

All the following steps are performed by the enzyme transposase during transposition of bacterial insertion sequences except

#Unit 2. Cellular Organization

  1. excision of the IS element from the donor DNA molecule.

  2. introduction of staggered cuts into the target DNA molecule.

  3. ligation of the IS element to the target DNA.

  4. synthesis of DNA to fill in the single-stranded gaps.

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TLS Online TPP Program

#Question id: 33476

#Unit 2. Cellular Organization

Find true and false statements
A. The structures of eukaryotic genes show extensive variation. 
B. Some eukaryotic genes are uninterrupted and their sequences are colinear with those of the corresponding mRNAs. 
C. Most multicellular eukaryotic genes are interrupted, but the introns vary enormously in both number and size.
TLS Online TPP Program

#Question id: 33477

#Unit 2. Cellular Organization

Finding: Ancestry have similar organizations with conservation of the positions (of at least some) of the introns.

Example: The globin and DHFR genes are examples of a genes that share a common ancestor
TLS Online TPP Program

#Question id: 33478

#Unit 2. Cellular Organization

Find true and false statements
A. Comparisons of related genes in different species show that the sequences of the corresponding exons are usually conserved
B. when two genes are related, the relationship between their exons is closer than the relationship between their introns.
C. The sequences of the introns are much less similar.
D. Introns evolve much more rapidly than exons because of the lack of selective pressure to produce a polypeptide with a useful sequence.
TLS Online TPP Program

#Question id: 33479

#Unit 2. Cellular Organization
TLS Online TPP Program

#Question id: 33480

#Unit 2. Cellular Organization

Finding: The overall degree of divergence between two homologous exons in related genes corresponds to the differences between the polypeptides.

Reason: Overall degree of divergence between two homologous exons is mostly a result of base substitutions.
TLS Online TPP Program

#Question id: 33481

#Unit 2. Cellular Organization

A. In homologous introns, the pattern of divergence involves both changes in length.
B. Divergence in introns is due to deletions and insertions and base substitutions. 
C. Introns are slowly evolve while exons much more rapidly 
D. When a gene is compared among different species, there are instances where its exons are homologous but its introns have diverged so much that very little homology is retained.