A plant produces flowers that are open through the day and the night. An experimenter places pollen on the stigmas of freshly opened flowers and covers them after pollination to prevent natural pollinators from having access to the flowers. When experimental pollination was carried out during the day, 40% of the flowers yielded fruit. When experimental pollination was carried out during the night, 80% of the flowers yielded fruit. However, when flowers were  kept  open  to  natural  pollination  during  the  day  (covered  at  night),  35%  of  flowers  produced  fruit.  20%  of flowers exposed to natural pollination during the night (covered during the day) produced fruit. Which of the following statements is NOT a plausible explanation of these results ?

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#Question id: 10838

#Unit 10. Ecological Principles

Fighting over shared resources is called

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#Question id: 4484

#Unit 3. Fundamental Processes

Match General Transcription Factors with their functions;

i. TAFs	A. Appears to regulate the binding of TBP to DNA. It does this using an inhibitory flap that binds to the DNA-binding surface of TBP, another example of molecular mimicry. This flap must be displaced for TBP to bind TATA.
ii. TFIIB	B. Insert into the RNA-exit channel and active center cleft of Pol II in a manner analogous to the sigma region 3/4 linker in the bacterial case.
iii. TFIIH	C.  As an ATP-driven translocator of double-stranded DNA.
iv. TFIIF	D. This two-subunit (in humans) factor associates with Pol II and is recruited to the promoter together with that enzyme.

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#Question id: 4384

#Unit 3. Fundamental Processes

Transcriptionally inactive genes

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#Question id: 15153

#Unit 8. Inheritance Biology

In this problem we will explore some of the many ways that mutations in two different genes can interact to produce different Mendelian ratios. Consider a hypothetical insect species that has red eyes. Imagine mutations in two different unlinked genes that can, in certain combinations, block the formation of red eye pigment yielding mutants with white eyes. In principle, there are two different possible arrangements for two biochemical steps responsible for the formation of red eye pigment. The two genes might act in series such that a mutation in either gene would block the formation of red pigment. Alternatively, the two genes could act in parallel such that mutations in both genes would be required to block the formation of red pigment.

Further complexity arises from the possibility that mutations in either gene that lead to a block in enzymatic activity could be either dominant or recessive. If the crosses is made between a wild type insect with red eyes and a true breeding white eyed strain with mutations in both genes. Such considerations yield the Pathways in parallel with recessive mutations in both genes, determine the phenotype of the F1 progeny and the expected phenotypic ratio of red to white eyed insects in the F2.

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#Question id: 23288

#Unit 8. Inheritance Biology

The staining of chromosomes with a special dye called Giemsa reveals G bands, which distinguish