diff --git a/pkg/obiformats/embl_read.go b/pkg/obiformats/embl_read.go
index 4150f57..fb22ccd 100644
--- a/pkg/obiformats/embl_read.go
+++ b/pkg/obiformats/embl_read.go
@@ -87,7 +87,7 @@ func EndOfLastFlatFileEntry(buff []byte) int {
 	return -1
 }
 
-func EmblChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
+func EmblChunkParser(withFeatureTable, UtoT bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
 	parser := func(source string, input io.Reader) (obiseq.BioSequenceSlice, error) {
 		scanner := bufio.NewScanner(input)
 		sequences := make(obiseq.BioSequenceSlice, 0, 100)
@@ -128,6 +128,9 @@ func EmblChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.BioS
 				parts := strings.SplitN(line[5:], " ", 7)
 				np := len(parts) - 1
 				for i := 0; i < np; i++ {
+					if UtoT {
+						parts[i] = strings.ReplaceAll(parts[i], "u", "t")
+					}
 					seqBytes.WriteString(parts[i])
 				}
 			case line == "//":
@@ -161,10 +164,10 @@ func EmblChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.BioS
 func _ParseEmblFile(
 	input ChannelFileChunk,
 	out obiiter.IBioSequence,
-	withFeatureTable bool,
+	withFeatureTable, UtoT bool,
 ) {
 
-	parser := EmblChunkParser(withFeatureTable)
+	parser := EmblChunkParser(withFeatureTable, UtoT)
 
 	for chunks := range input {
 		order := chunks.Order
@@ -206,6 +209,7 @@ func ReadEMBL(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, er
 			entry_channel,
 			newIter,
 			opt.WithFeatureTable(),
+			opt.UtoT(),
 		)
 	}
 
diff --git a/pkg/obiformats/fastaseq_read.go b/pkg/obiformats/fastaseq_read.go
index a2fc3be..8c8441c 100644
--- a/pkg/obiformats/fastaseq_read.go
+++ b/pkg/obiformats/fastaseq_read.go
@@ -39,7 +39,7 @@ func EndOfLastFastaEntry(buffer []byte) int {
 	return last
 }
 
-func FastaChunkParser() func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
+func FastaChunkParser(UtoT bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
 
 	parser := func(source string, input io.Reader) (obiseq.BioSequenceSlice, error) {
 		var identifier string
@@ -131,7 +131,9 @@ func FastaChunkParser() func(string, io.Reader) (obiseq.BioSequenceSlice, error)
 					if C >= 'A' && C <= 'Z' {
 						C = C + 'a' - 'A'
 					}
-
+					if UtoT && C == 'u' {
+						C = 't'
+					}
 					if (C >= 'a' && C <= 'z') || C == '-' || C == '.' || C == '[' || C == ']' {
 						seqBytes.WriteByte(C)
 					} else {
@@ -170,6 +172,9 @@ func FastaChunkParser() func(string, io.Reader) (obiseq.BioSequenceSlice, error)
 					if C >= 'A' && C <= 'Z' {
 						C = C + 'a' - 'A'
 					}
+					if UtoT && C == 'u' {
+						C = 't'
+					}
 					// Removing white space from the sequence
 					if (C >= 'a' && C <= 'z') || C == '-' || C == '.' || C == '[' || C == ']' {
 						seqBytes.WriteByte(C)
@@ -207,9 +212,10 @@ func FastaChunkParser() func(string, io.Reader) (obiseq.BioSequenceSlice, error)
 func _ParseFastaFile(
 	input ChannelFileChunk,
 	out obiiter.IBioSequence,
+	UtoT bool,
 ) {
 
-	parser := FastaChunkParser()
+	parser := FastaChunkParser(UtoT)
 
 	for chunks := range input {
 		sequences, err := parser(chunks.Source, chunks.Raw)
@@ -243,7 +249,7 @@ func ReadFasta(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 
 	for i := 0; i < nworker; i++ {
 		out.Add(1)
-		go _ParseFastaFile(chkchan, out)
+		go _ParseFastaFile(chkchan, out, opt.UtoT())
 	}
 
 	go func() {
diff --git a/pkg/obiformats/fastqseq_read.go b/pkg/obiformats/fastqseq_read.go
index f7f79fb..c092e32 100644
--- a/pkg/obiformats/fastqseq_read.go
+++ b/pkg/obiformats/fastqseq_read.go
@@ -131,7 +131,7 @@ func _storeSequenceQuality(bytes *bytes.Buffer, out *obiseq.BioSequence, quality
 	out.SetQualities(q)
 }
 
-func FastqChunkParser(quality_shift byte, with_quality bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
+func FastqChunkParser(quality_shift byte, with_quality bool, UtoT bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
 	parser := func(source string, input io.Reader) (obiseq.BioSequenceSlice, error) {
 
 		var identifier string
@@ -209,6 +209,9 @@ func FastqChunkParser(quality_shift byte, with_quality bool) func(string, io.Rea
 					if C >= 'A' && C <= 'Z' {
 						C = C + 'a' - 'A'
 					}
+					if C == 'u' && UtoT {
+						C = 't'
+					}
 					seqBytes.Reset()
 					seqBytes.WriteByte(C)
 					state = 6
@@ -228,6 +231,9 @@ func FastqChunkParser(quality_shift byte, with_quality bool) func(string, io.Rea
 					if C >= 'A' && C <= 'Z' {
 						C = C + 'a' - 'A'
 					}
+					if C == 'u' && UtoT {
+						C = 't'
+					}
 					if (C >= 'a' && C <= 'z') || C == '-' || C == '.' || C == '[' || C == ']' {
 						seqBytes.WriteByte(C)
 					} else {
@@ -301,10 +307,10 @@ func _ParseFastqFile(
 	input ChannelFileChunk,
 	out obiiter.IBioSequence,
 	quality_shift byte,
-	with_quality bool,
+	with_quality, UtoT bool,
 ) {
 
-	parser := FastqChunkParser(quality_shift, with_quality)
+	parser := FastqChunkParser(quality_shift, with_quality, UtoT)
 
 	for chunks := range input {
 		sequences, err := parser(chunks.Source, chunks.Raw)
@@ -342,6 +348,7 @@ func ReadFastq(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 			out,
 			obidefault.ReadQualitiesShift(),
 			opt.ReadQualities(),
+			opt.UtoT(),
 		)
 	}
 
diff --git a/pkg/obiformats/genbank_read.go b/pkg/obiformats/genbank_read.go
index 6c23ef6..6c308dd 100644
--- a/pkg/obiformats/genbank_read.go
+++ b/pkg/obiformats/genbank_read.go
@@ -29,7 +29,7 @@ const (
 
 var _seqlenght_rx = regexp.MustCompile(" +([0-9]+) bp")
 
-func GenbankChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
+func GenbankChunkParser(withFeatureTable, UtoT bool) func(string, io.Reader) (obiseq.BioSequenceSlice, error) {
 	return func(source string, input io.Reader) (obiseq.BioSequenceSlice, error) {
 		state := inHeader
 		scanner := bufio.NewReader(input)
@@ -165,6 +165,9 @@ func GenbankChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.B
 					parts := strings.SplitN(line[10:], " ", 6)
 					lparts := len(parts)
 					for i := 0; i < lparts; i++ {
+						if UtoT {
+							parts[i] = strings.ReplaceAll(parts[i], "u", "t")
+						}
 						seqBytes.WriteString(parts[i])
 					}
 					processed = true
@@ -200,9 +203,9 @@ func GenbankChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.B
 
 func _ParseGenbankFile(input ChannelFileChunk,
 	out obiiter.IBioSequence,
-	withFeatureTable bool) {
+	withFeatureTable, UtoT bool) {
 
-	parser := GenbankChunkParser(withFeatureTable)
+	parser := GenbankChunkParser(withFeatureTable, UtoT)
 
 	for chunks := range input {
 		sequences, err := parser(chunks.Source, chunks.Raw)
@@ -242,6 +245,7 @@ func ReadGenbank(reader io.Reader, options ...WithOption) (obiiter.IBioSequence,
 			entry_channel,
 			newIter,
 			opt.WithFeatureTable(),
+			opt.UtoT(),
 		)
 	}