Date of Award

Spring 2010

Document Type

Restricted Thesis

Terms of Use

© 2010 Jennifer E. Spindel. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Nicholas J. Kaplinsky


Barren unbranched (Ba-ub) is a new, semi-dominant maize mutant that produces either an unbranched tassel and no ear, or fasciated tassels and ears, depending on the genetic background. In a W22xA632 mapping population, tassels and ears are fasciated, and increased spikelet density is found across the tassel rachi and branches, as a result of increased spikelet pair meristem initiation. Ba-ub mapping population tassels also make fewer tassel branches than normal, and branch angle is increased. Spikelet density is increased in the ear, and most mutants produce three silks per kernel, reflecting a likely increase in floral meristem size, proliferation, or branching. Ba-ub roots were found to be agravitropic. Positional cloning places Ba-ub on the long arm of chromosome four, in a region between 195 and 226 Mb.