There are about 90 million rod cells in the human retina, and each contains about 4x107 molecules of rhodopsin that are very densely packed in the membrane disks.

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#Id: 9812

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There are five phytochrome isoforms in angiosperms

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#Id: 9813

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PHYA is the only gene that encodes a Type I phytochrome and predominantly perceives far-red light.

Phytochrome B predominantly perceives red light

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#Id: 9814

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The PHYA gene is transcriptionally active in dark-grown seedlings, but its expression is strongly inhibited in the light in monocots.

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#Id: 9815

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The PRD domain of phyB serve as an NLS. 

Conversion of Pr to Pfr by red light expose the functional NLS of the PRD domain of phyB, facilitating phyB’s import into the nucleus.

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#Id: 9816

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PRD domain of phyA cannot act as an NLS, so to transport it into the nucleus requires FARRED ELONGATED HYPOCOTYL1 (FHY1) and its homolog FHY1-LIKE (FHL),

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#Id: 9817

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Phytochrome responses fall into three major categories based on the amount of light they require: very low fluence responses (VLFRs), low-fluence responses (LFRs), and high-irradiance responses (HIRs).