Since the SRB parents each randomly select one of their (s) genes and one of their (rb) genes to pass on, then each offspring always gets (s)(s)+(rb)(rb) to start with.
(the SRB parents; randomly select; one of their (s) genes and one of their (rb) genes) (one of their (s) genes and one of their (rb) genes; to pass on; ) (each offspring; gets; T:Since the SRB parents each randomly select one of their (s) genes and one of their (rb) genes to pass on; T:then; T:always)
the SRB parents one of their (s) genes and one of their (rb) genes each offspring
randomly select to pass on gets
one of their (s) genes and one of their (rb) genes
T:Since the SRB parents each randomly select one of their (s) genes and one of their (rb) genes to pass on T:then T:always