THE BIG IDEA!!!!!!!

Transcription From DNA to RNA

What is RNA? Ribonucleic acid (RNA)

Structure of RNA 1 strand Phosphate group 5 carbon Sugar (ribose) Nitrogen base

What are the bases? Adenine (A) Guanine (G) Cytosine (C) Uracil (U)

Which are purines? Adenine and Guanine 2 rings

Which are pyrimidines Cytosine and Uracil 1 ring

Which bases pair? A, U G, C When transcribing RNA, U replaces T

Step one RNA polymerase binds at a promoter A region of DNA that says start

Step 2 RNA polymerase unwinds the DNA Exposes the nucleotides

Step 3 RNA polymerase adds complimentary RNA nucleotides

When is transcription finished? RNA polymerase reaches the stop signal and detaches from the DNA RNA is released DNA double helix Reforms Watch

Does RNA polymerase transcribe all of the DNA? NO Uses one part of one strand of DNA (the gene)

Does all the DNA transcribed code for proteins? NO! Introns Long segments of “junk” DNA that have no coding info.

What DNA does code for proteins? Exons DNA that codes for proteins

When are the Introns removed? Before the mRNA leaves the nucleus An enzyme cuts out the introns & puts exons together

ACTIVITY Materials: masking tape, pens or pencils (two colors), metric ruler, scissors Procedure Place a 15-20cm piece of masking tape on your desk. This represents a gene Use two colors to write appropriately joined One color represents introns, one exons Space the letters so they take up the entire piece of tape Lift the tape Working from left to right cut apart the groups of letters in the same color Stick the pieces to a piece of paper as you cut them making two strips according to color. Join the pieces in their original order. 1. Label the strand that is the intron and label the strand that is the exon. 2. Predict what might happen to a protein if an intron were not removed. Turn into the box.