Changes in gene copy number alter microtubule activity. (A) Representative image of a wild-type cell expressing Bik1-3GFP. Red line indicates measured length between plus-end and spindle pole body. Scale bar = 1 µm. Image is a maximum intensity projection of z series. (B) Life plot of a single microtubule from a wild-type cell. Microtubule lengths were measured at 5-s intervals. (C) Histogram of all astral microtubule lengths from time lapse imaging of wild type, TUB1/tub1Δ, TUB2/tub2Δ, and TUB1/tub1Δ TUB2/tub2Δ. Data are from at least three separate experiments for each genotype, and a total of at least 20 cells were analyzed for each genotype. (D) Polymerization rates of astral microtubules. Each dot represents a single polymerization event, and dots are colored by experimental day. P value between wild type and mutant based on t test after one-way ANOVA. Bars are median ±95% CI. (E) Representative image of quantitative Western blot of α-tubulin in wild-type cells to determine molecules per cell. Known mass of purified yeast tubulin was used to make a standard curve. (F) Representative image of quantitative Western blot of β-tubulin in wild-type cells to determine molecules per cell. Known mass of purified yeast tubulin was used to make a standard curve. (G) Paired molecules of α- or β-tubulin per cell for each genotype. Protein mass (ng) was converted to molecules per cell. Data represent at least two independent experiments with two biological replicates, and each dot is mean molecules per cell calculated from at least three dilutions in that experiment. Dots are colored by experiment. (H) Ratio of α-to β-tubulin in cells with indicated genotypes. Ratios were calculated from data in G. Bars are mean ± 95% CI. Source data are available for this figure: SourceData F2.