rosalind练习题二十一

# Problem

# A DNA string is a reverse palindrome if it is equal to its reverse complement. For instance, GCATGC is a reverse palindrome because its reverse complement is GCATGC. See Figure 2.

# Given: A DNA string of length at most 1 kbp in FASTA format.

# Return: The position and length of every reverse palindrome in the string having length between 4 and 12. You may return these pairs in any order.

# Sample Dataset

# >Rosalind_24

# TCAATGCATGCGGGTCTATATGCAT

# Sample Output

# 4 6

# 5 4

# 6 6

# 7 4

# 17 4

# 18 4

# 20 6

# 21 4

# 这道题目给定一个长度不超过1000bp的DNA序列，要求找到其中所有的反向回文序列，然后输出它们在原序列中的位置和长度。反向回文序列指的是与其反向互补序列相等的序列，比如GCATGC就是一个反向回文序列，因为它的反向互补序列也是GCATGC。需要注意的是，找到的所有反向回文序列的长度必须在4到12之间，并且输出的顺序可以任意安排。

from Bioimport SeqIO

def reverse_complement(s):

return s.translate(str.maketrans("ATCG", "TAGC"))[::-1]

def find_reverse_palindromes(seq):

res = []

for iin range(len(seq)):

for jin range(4, 13):

if i+j >len(seq):

break

            subseq = seq[i:i+j]

if subseq == reverse_complement(subseq):

res.append((i+1, j))

return res

# 读取FASTA文件

record = SeqIO.read("input6.fasta", "fasta")

seq =str(record.seq)

# 找到所有的反向回文序列

res = find_reverse_palindromes(seq)

# 输出结果

for pos, lengthin res:

print(pos, length)