Answer:
The function is as follows:
def count_bases(DNA_str):
retDNA = {}
for i in DNA_str:
if i in retDNA:
retDNA[i]+=1
else:
retDNA[i] = 1
return retDNA
Step-by-step explanation:
This defines the function
def count_bases(DNA_str):
This initializes a dictionary
retDNA = {}
This iterates through the dictionary
for i in DNA_str:
If an item exists in the dictionary
if i in retDNA:
The count is updated by 1
retDNA[i]+=1
Otherwise
else:
The count is set to 1
retDNA[i] = 1
This returns the DAN
return retDNA