Morning Extra - Should research continue on hybrid embryos?

Researchers say work on human-animal embryos is needed to advance the understanding of complex diseases such as Parkinson's, Alzheimer's and Motor Neurone Disease. But critics say it involves the needless destruction of human life, and is fraught with moral difficulties. Plus: Is graffiti art or vandalism? A campaign is underway to reduce the sentence of a notorious Glasgow graffiti artist who has been jailed for 28 months after spray painting trains and railway stations. Is the sentence too heavy? Does graffiti art brighten-up our cities or is it mindless vandalism? Gary Robertson takes your calls, texts and emails.