diff --git a/README.md b/README.md
index ae47319..ef676bf 100644
--- a/README.md
+++ b/README.md
@@ -94,7 +94,8 @@ backward-compatibility then you may load it directly by accession (`NC_001807.4`
 The rCRS mitochondria sequence contains an 'N' base at position 3106-3107 to
 preserve legacy nucleotide numbering. This can be useful for using legacy
 coordinates but but is impractical when working with sequences that are
-expected to align to observed human mitochondrial sequences. SeqSeek removes this `N`:
+expected to align to observed human mitochondrial sequences. SeqSeek
+removes this `N` unless it is explicitly requested by passing `RCRS_N_remove=False`.
 
 ```python
 Chromosome('MT').sequence(3106, 3107)  # => ''
diff --git a/seqseek/chromosome.py b/seqseek/chromosome.py
index 007c6fa..34607f9 100644
--- a/seqseek/chromosome.py
+++ b/seqseek/chromosome.py
@@ -2,7 +2,8 @@
 
 from .exceptions import TooManyLoops, MissingDataError
 from .lib import (BUILD37, BUILD38, get_data_directory, sorted_nicely,
-                 BUILD37_ACCESSIONS, BUILD38_ACCESSIONS, ACCESSION_LENGTHS, RCRS_ACCESSION)
+                  BUILD37_ACCESSIONS, BUILD38_ACCESSIONS, ACCESSION_LENGTHS,
+                  RCRS_ACCESSION, MITOCHONDRIA_NAMES)
 
 
 class Chromosome(object):
@@ -12,7 +13,7 @@ class Chromosome(object):
         BUILD38: BUILD38_ACCESSIONS
     }
 
-    def __init__(self, chromosome_name, assembly=BUILD37, loop=False):
+    def __init__(self, chromosome_name, assembly=BUILD37, loop=False, RCRS_N_remove=True):
         """
         Usage:
 
@@ -28,6 +29,7 @@ def __init__(self, chromosome_name, assembly=BUILD37, loop=False):
         self.name = str(chromosome_name)
         self.assembly = assembly
         self.loop = loop
+        self.RCRS_N_remove = RCRS_N_remove
 
         self.validate_assembly()
         self.validate_name()
@@ -56,7 +58,7 @@ def validate_name(self):
                         name=self.name))
 
     def validate_loop(self):
-        if self.loop and self.name != 'MT':
+        if self.loop and self.name not in MITOCHONDRIA_NAMES:
             raise ValueError('Loop may only be specified for the mitochondria.')
 
     def validate_coordinates(self, start, end):
@@ -87,7 +89,7 @@ def sorted_chromosome_length_tuples(cls, assembly):
                               ACCESSION_LENGTHS.keys()).index(name_to_accession[pair[0]]))
 
     def filename(self):
-       return '{}.fa'.format(self.accession)
+        return '{}.fa'.format(self.accession)
 
     def path(self):
         data_dir = get_data_directory()
@@ -127,7 +129,7 @@ def sequence(self, start, end):
         # The rCRS mito contig contains an 'N' base at position 3107 to preserve legacy
         # nucleotide numbering. We remove it because it is not part of the observed
         # sequence. See http://www.mitomap.org/MITOMAP/HumanMitoSeq
-        if self.accession == RCRS_ACCESSION:
+        if self.accession == RCRS_ACCESSION and self.RCRS_N_remove is True:
             sequence = sequence.replace('N', '')
 
         return sequence
diff --git a/seqseek/lib.py b/seqseek/lib.py
index 03ece83..93a70cd 100644
--- a/seqseek/lib.py
+++ b/seqseek/lib.py
@@ -152,6 +152,9 @@
     'NT_167251.1': 1680828,
 }
 
+MITOCHONDRIA_NAMES = {'MT', 'RSRS', BUILD37_ACCESSIONS['MT'], BUILD37_ACCESSIONS['RSRS'],
+                      BUILD38_ACCESSIONS['MT'], BUILD38_ACCESSIONS['RSRS']}
+
 
 def get_data_directory():
     default = os.path.expanduser(DEFAULT_DATA_DIR)
diff --git a/seqseek/tests/test_functional.py b/seqseek/tests/test_functional.py
index 67d5a75..d68858b 100644
--- a/seqseek/tests/test_functional.py
+++ b/seqseek/tests/test_functional.py
@@ -71,6 +71,12 @@ def test_chrMT_sequence(self):
         seq = Chromosome('MT').sequence(5, 10)
         self.assertEqual(seq, expected_seq)
 
+    def test_rCRS_sequence_retain_N(self):
+        expected_seq = 'GATCACAGGTCTNTCACCCT'
+        seq = Chromosome('MT', RCRS_N_remove=False).sequence(0, 20)
+        self.assertEqual(seq, expected_seq)
+        self.assertTrue('N' in seq)  # the N base was *not* removed
+
     def test_mito_loop_end(self):
         expected_seq = 'CTTCACCCTGATCACAGGT'
 
diff --git a/setup.py b/setup.py
index c642b9c..eb9fbc9 100755
--- a/setup.py
+++ b/setup.py
@@ -15,9 +15,9 @@
 
 setup(
     name='seqseek',
-    version='0.3.3',
+    version='0.4.1',
     url='https://github.com/23andMe/seqseek',
-    download_url = 'https://github.com/23andMe/seqseek/tarball/0.3.3',
+    download_url = 'https://github.com/23andMe/seqseek/tarball/0.4.1',
     author='23andMe Engineering',
     author_email=['mstrand@23andme.com'],
     description='Easy access to human reference genome sequences',