Hi Rubina,
Normally this will not cuase any problem. There is no data integrity issue due to Replication and Backup activity happening together at one time. The risk is only for the amount of transaction taking place during the backup period.
If the backup of db takes less time, there woun't be any issue. DB intigrity will not affected due to Backup Database action. It will backup the data which are completed the transaction at the moment.