Transcription

Section 8.4:

Central Dogma

Information flows in one direction:

1. Replication copies DNA

2. Transcription converts DNA into RNA

3. Translation interprets RNA message into string of amino acids or proteins

What is a gene?A section of DNA that contains instructions on

how to make a specific protein.

Each gene has a locus (location) on DNA

Alleles are different forms of a gene

DNA located in the nucleus only

What is transcription?Process of copying a

sequence of DNA (gene) to produce strand of RNA

RNA is a copy of a gene, not the entire strand of DNA.

Strand of RNA is complementary to DNA strand

Small segment can exit nucleus into cytoplasm

Steps of Transcription

1. RNA Polymerase recognizes the start of the gene, attaches to the DNA strand and begins to unwind and unzip using helicase.

2. RNA Polymerase adds RNA nucleotides to section of DNA being used as template.

3. Transcription complex moves along DNA, adding nucleotides, until complete gene is copied.

4. Complete mRNA strand breaks off and moves out of nucleus.

What does transcription produce?

mRNA – message that is ultimately translated into a protein

Practice transcribing……Don’t forget to swap U for

T

DNA: A C G T T A C A G

RNA: U G C A A U G U C

http://www.youtube.com/watch?v=4PKjF7OumYo

Reflection #2Define Replication:Create the complementary strand for the DNA

sequence:

(original) A G C C T C A G T T C A G(new)Define Transcription:Translate the complementary strand from above into

mRNA:

(new)(mRNA)