mˌaɪkɹoʊtˈuːbjuːlz fˈɔːɹmd fɹʌm pjˈʊɹ tˈuːbjʊlˌɪn ˌʌndɚɡˈoʊ sˈʌbjuːnˌɪt ˈʌpteɪk ænd lˈɔs æɾ ˈɛndz baɪ bˈoʊθ ɹˈændəm ɛkstʃˈeɪndʒ dᵻfjˈuːʒən, ænd baɪ ɐ dᵻɹˈɛkʃənəl tɹˈɛdmɪlɪŋ ˈɛlɪmənt.
Microtubules formed from pure tubulin undergo subunit uptake and loss at ends by both random exchange diffusion, and by a directional (treadmilling) element.