1.

a.

Iterate over each character in the sequence from the beginning to end, replacing each A, T, G, and C with its T, A, C, and G, respectively.

b.

No!

c.

def complement(sequence):
    """ (str) -> str

    Return the complement of sequence.

    >>> complement('AATTGCCGT')
    'TTAACGGCA'
    """ 

    complement_dict = {'A': 'T', 'T': 'A', 'C': 'G', 'G': 'C'}
    sequence_complement = ''

    for char in sequence:
        sequence_complement = sequence_complement + complement_dict[char]

    return sequence_complement

2.

a.


index = 0
smallest = L[0]

for i in range(1, len(L)):
    if L[i] < smallest:
        index = i
        smallest = L[i]

b.

def min_index(L):
    """ (list) -> (object, int)

    Return a tuple containing the smallest item from L and its index.

    >>> min_index([4, 3, 2, 4, 3, 6, 1, 5])
    (1, 6)
    """ 

    index = 0
    smallest = L[0]

    for i in range(1, len(L)):
        if L[i] < smallest:
            index = i
            smallest = L[i]

    return (smallest, index)