Kvon et al., 2023 Biol 471 (Test questions with correct solutions)

How are python limbs different from most snake species? correct answers Pythons retain vestigial pelvic and femur structures while advanced snakes have lost nearly all skeletal limb structures What is the zone of polarizing activity regulating sequence (ZRS)? correct answers A long distance transcriptional enhancer in mammals that controls expression of Shh in developing limb buds. It is limb specific, located nearly 1 M bps from promoter, and active on posterior limb bud mesenchyme How is the topic of Leal and Cohn similar to Kvon? correct answers Leal and Cohn look at how sequence changes in limb-specific enhancers (ZRS and Hoxd) for Shh contribute to limb loss in snakes. Both studies reveal how mutations in functional non-coding sequences, even when poorly conserved, can disrupt transcriptional networks required for organismal development What are some examples of limb morphological adaptations in other species previously reported? correct answers Bat wings: repurposed hands Primates (aye-aye): finger morphology radically diverged Salamanders, lizards, cetaceans: limb atrophy What human congenital abnormalities arise with Shh regulatory region mutations? correct answers Include limb malformations such as preaxial polydactyly, numerous single nt polymorphisms in ZRS itself, and duplications and deletions in others What is the goal of the Kvon paper? correct answers To study the molecular and functional evolution of a critical limb enhancer in snakes and examine its possible role in limb loss. They demonstrated how transplanting snake-specific limb enhancers into mice can recapitulate limb truncation Compare/contrast the ZRS enhancer sequence of basal snakes with advanced snakes. correct answers In basal snakes, the ZRS enhancer shares ~80% nt identity with orthologous regions from limbed lizards and shows substitution rates similar to other vertebrae ZRS orthologs. In advanced snakes, there are substantially increased substitutions compared to other enhancers and a loss of evolutionary constraint on enhancer Basal snake examples correct answers Boa and python Advanced snake examples correct answers Viper, rattlesnake, king cobra, and corn snake Define ortholog correct answers Any of 2 or more homologous gene sequences found in different species related by linear descent. The same gene or protein in different species.