Why doesn't this work?
> samples$geno <- as.data.frame(sapply(yo, toupper), col.names="geno")
> samples
                          quant_samples   age sapply(yo, toupper)
E11.5 F20het BA40     E11.5 F20het BA40 E11.5              F20HET
E11.5 F20het BA45     E11.5 F20het BA45 E11.5              F20HET