An organism has been found to contain a defective form of photolyase. What function might be impaired in this organism?
A. Lengthening of the tips of chromosomes
B. Repair of DNA damage caused by UV light
C. Stabilization of single-stranded DNA during DNA replication
D. Recognition of damaged DNA by the UvrABC complex
Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain?
Gather Content
· What do you already know about photolyase?
Consider Possibilities
· Consider the different answer options. Which can you rule out?
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
B. Repair of DNA damage caused by UV light
Clarify Question
· What is the key concept addressed by the question?
o This question addresses the function of photolyase.
· What type of thinking is required?
o Although you may not have seen this example before, you know enough about the concept to Apply your knowledge and understanding to this unfamiliar situation.
· What key words does the question contain?
o Photolyase is an enzyme in the photorepair pathway.
Gather Content
· What do you already know about photolyase?
o Photolyase is an enzyme in the photorepair pathway.
o It recognizes thymine dimers – the main damage caused by UV light – and repairs them.
Consider Possibilities
· Consider the different answer options. Which can you rule out?
o Does photolyase lengthen the tips of chromosomes? No, that’s telomerase.
o Does photolyase stabilize single-stranded DNA? No, those are the SSBs, single-stranded DNA binding proteins.
o Does photolyase recognize damaged DNA with the UvrABC complex? Close, but that is a different DNA repair pathway.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Without photolyase, the organism would be less equipped to repair UV-induced DNA damage.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o This question required you to Apply your knowledge and understanding to this unfamiliar situation.
o Did you remember that photolyase recognizes and fixes the DNA damage caused by UV light?
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Class I major histocompatibility complex molecules are found on ________ cells.
A. all anucleated B. all nucleated C. antigen-presenting D. None of the choices are correct.
In what way can defective transportable elements alter genomes even if they cannot mobilize? (Select all that apply.)
A) Crossing-over between transportable elements on the same chromosome can result in a deletion or an inversion. B) Crossing-over between transportable elements on non homologous chromosomes can result in a reciprocal translocation. C) Genes located between two transportable elements could be moved to a non homologous chromosome. D) Proteins produced by the defective transposable elements introduce point mutations in other areas of the genome.
Which method of gene transfer involves direct contact between the bacteria?
a. Conjugation. b. Transformation. c. Transduction.
Structures that may be visible under the microscope and indicate where crossing over has occurred.
A. chiasma B. homologue C. kinetochore D. synapsis E. synaptonemal