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TranscriptionPacket #10Chapter #8

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IntroductionTranscription

Transcription is a process that occurs within the nucleus of a cell where a single strand of DNA is used to produce a complementary strand of RNA. The type of RNA

produced is mRNA.

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Types of RNAmRNA

Messenger RNA An RNA molecule

transcribed from the DNA of a gene

Once mRNA is complete, proteins are translated from mRNA by the help of RIBOSOMES

Types of RNA

mRNA

snRNA

tRNA

rRNA

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The Gene

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Chromosome ReviewDNA strands are

composed of segments known as genes.

Chromosome

Chromatin

DNA Molecules

DNA Strands

Genes

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GenesGenes, used during the

process of transcription, have two major segments.Regulatory regionCoding region

Both regions play a role during transcription.

Within the regulatory region, there is a special region known as the promoter region.

DNA Strands Genes

Regulatory Region

Promoter Region

Coding Region

Terminator

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Strands of TranscriptionTemplate Strand

In transcription, known as the Complementary Strand (cDNA)

A molecular “mold” that shapes the structure or sequence of another molecule

Controls the nucleotide sequence of RNA during transcription

Alignment guide“GUIDE”

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Strands of TranscriptionComplementary Strand (cDNA)

DNA transcribed from a specific RNA strandComplementary Strand (cRNA)

RNA transcribed from a specific DNA single-stranded template

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TranscriptionThe Process

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The Process RNA Polymerase, the only

enzyme used during transcription, binds at the promoter region (sequence) and unzips the DNA strand

RNA Polymerase works downstream adding RNA nucleotides to the 3’ end of the newly formed RNA strand New RNA strand grows in the

5’ to 3’ direction RNA Polymerase hits the

“Terminator” sequence that signals the end of transcription

Newly made RNA is released. This RNA is called pre-mRNA.

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Post-Transcription

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Post-Transcription IThe new RNA strand

is called pre-mRNAWhy? Because the

pre-mRNA needs to be “groomed” for the moment of Translation

Unneeded RNA nucleotide segments, known as introns, need to be removed.

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Post-Transcription IIThe introns are removed and

the exons, the good regions, are joined together in a process known as splicing.Process completed using the

enzyme known as spliceosome. Spliceosome contains snRNA.

The completed mRNA leaves the nucleus and enters into the cytoplasm ready for translation.

The mRNA carries the genetic code with it.

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Review