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TLS Online TPP Program

#Question id: 5002

All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.

The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information above, which explanation is most likely?

#Unit 11. Evolution and Behavior

  1. Pax-6 in all of these animals is not homologous; it arose independently in many different animal phyla due to intense selective pressure favoring vision.

  2. The Pax-6 gene is really not ʺoneʺ gene. It is many different genes that, over evolutionary time and due to convergence, have come to have a similar nucleotide sequence and function.

  3. The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian. Animals with eyes or eyespots are descendants of this ancestor.

  4. The perfectly designed Pax-6 gene appeared instantaneously in all animals created to have eyes or eyespots.

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TLS Online TPP Program

#Question id: 4152

#Unit 3. Fundamental Processes

The pathway for polypeptides exported from E. coli includes the following steps, which occur in what order for correct export?

1.  A chaperone, SecA, binds to the polypeptide.

2.  A chaperone, SecB, binds to the polypeptide.

3.  ATP is hydrolyzed by Sec A.

4.  SecA pushes 20 amino acids of the polypeptide into the translocation complex.
TLS Online TPP Program

#Question id: 4155

#Unit 3. Fundamental Processes

Of all the possible triplet codons, __ do not code for an amino acid.
TLS Online TPP Program

#Question id: 4156

#Unit 3. Fundamental Processes

The reading frame of DNA is fixed by
TLS Online TPP Program

#Question id: 4157

#Unit 3. Fundamental Processes

At the ribosome, the codon and anticodon associate by __.
TLS Online TPP Program

#Question id: 4158

#Unit 3. Fundamental Processes

What is a reasonable number of nucleotides in a tRNA molecule?
TLS Online TPP Program

#Question id: 4159

#Unit 3. Fundamental Processes

Which statement is not true about the ʺwobbleʺ position?