The default for seq objects in BioPython - just like in Python -  is for seq objects to be read only or immutable to avoid changing the sequence data. However, it is possible to convert it into a mutable sequence. 

Converting a seq object into a mutable seq object : 

```python
from Bio.Seq import MutableSeq
seq1 = Seq("GCCATTGTAATGGGCCGCTGAAAGGGTGCCCGA")
mutable_sequence = MutableSeq(seq1)
print(mutable_sequence)
mutable_sequence[0] = "A"
print(mutable_sequence)
```

Creating a mutable seq object from a string : 

```python
from Bio.Seq import MutableSeq
mutable_sequence2 = MutableSeq("GCCATTGTAATGGGCCGCTGAAAGGGTGCCCGA")
print(mutable_sequence2)
```

When printed in Python, the result will be:

```python
GCCATTGTAATGGGCCGCTGAAAGGGTGCCCGA
ACCATTGTAATGGGCCGCTGAAAGGGTGCCCGA
GCCATTGTAATGGGCCGCTGAAAGGGTGCCCGA
```

Boston University

-      Complements and Reverse Complements 
-      Transcription
-      Translation 
-      Translation Table 
-      Mutable Seq Objects 

How Sequences Differ from Strings 

This link leads to a page describing a large overview of BioPython and what it can do : 
http://biopython.org/DIST/docs/tutorial/Tutorial.html

BioPython Tutorial 

When working with nucleotide sequences, you can obtain the complements of the sequence : 

```python
my_seqq = Seq("GATCGATATATAGGAAATCGC")
print(my_seqq.complement()) 
```

You can also obtain the reverse complements : 

```python
print(my_seqq.reverse_complement()) 
```

When printed out, the result will be : 

```python
CTAGCTATATATCCTTTAGCG
GCGATTTCCTATATATCGATC
``` 

Complements and Reverse Complements 

Creating the coding and the template DNA strands : 

```python
coding_dna = Seq("ATGAGCCGCTGAAAGGGTGCCCGATAG")
template_dna = coding_dna.reverse_complement()
print(coding_dna)
print(template_dna)
```

Transcribing the coding strand into the mRNA strand (by replacing T with U) : 

```python
messengar_rna = coding_dna.transcribe()
print(messengar_rna)
```

You can also transcribe by starting with the template strand : 

```python
print(template_dna.reverse_complement().transcribe())
```

When printed out, the result will be: 
```python
ATGAGCCGCTGAAAGGGTGCCCGATAG
CTATCGGGCACCCTTTCAGCGGCTCAT
AUGAGCCGCUGAAAGGGUGCCCGAUAG
AUGAGCCGCUGAAAGGGUGCCCGAUAG
```

Transcription 

Translating the messenger rna into a protein sequence : 

```python
messenger_rna = Seq("AUGGCCAUUGUAAUGGUAG")
messenger_rna.translate()
print(messenger_rna.translate())
```

Translating from the DNA coding sequence : 

```python
coding_dna = Seq("ATGGCCATTGTAATGGTAG")
coding_dna.translate()
print(coding_dna.translate())
```

When dealing with different types of sequences, the specific translation table can be specified : 

```python
coding_dna.translate(table="Vertebrate Mitochondrial")
print (coding_dna.translate(table="Vertebrate Mitochondrial"))
```

You can also stop translating when it gets to the first in frame stop codon : 

```python
coding_dna2 = Seq("ATGGCCATTGTAATGGGCCGCTGAAAGGGTGCCCGATAG")
translate_2 = coding_dna2.translate(to_stop = True)
print(translate_2)
```

When printed, the result will be :

```python
MAIVMV
MAIVMV
MAIVMV
MAIVMGR
```


Translation 

Learn Before

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