8.4 Transcription

Classwork

• On pg. 6 of your notebooks- Split page into 3 sections:

– Top1/3- Draw fig 8.10 (pg.239)- color code

– Middle 1/3 - Make a double-bubble map comparing and contrasting DNA and RNA (239-240)

8.4 Transcription•Set up Cornell Notes on pg. 7

•Topic: 8.4 Transcription

•Essential Question:

1.What is the central dogma?

2.Why can an mRNA strand made during transcription, be thought of as a mirror image of the DNA strand from which it was made?

2.1 Atoms, Ions, and Molecules

8.4 Transcription

KEY CONCEPT Transcription converts a gene into a single-stranded RNA molecule.

3.2 Cell Organelles

rough endoplasmic reticulum

Have bumps called

ribosomes which

link amino acids together

to form proteins

REVIEW:

8.4 Transcription

Proteins are used for movement, eyesight,

and digestion and practically everything else you do.

8.4 Transcription

nucleotide

unzips

nucleotidesReview: Replication

Helicase

8.4 Transcription

2. DNA polymerase (pol-uh-mer-ase) enzymes bond the nucleotides together to form the new double helix.

DNA polymerase

new strand nucleotide

complementary

8.4 Transcription

original strand new strand

Two molecules of DNA

3. Two new molecules of DNA are formed, each with an original “parent” strand and a complementary newly formed “daughter” strand.

complementary

Why do we call the new “daughter” strand a complementary strand and not an identical strand?

8.4 Transcription

KEY CONCEPT Transcription converts a gene into a single-stranded RNA molecule.

RNA

DNA

8.4 Transcription

RNA carries DNA’s instructions.

• The central dogma states that information flows in one direction from

DNA to

RNA to

proteins.

8.4 Transcription

• The central dogma includes three processes.

• RNA is a link between DNA and proteins.

replication

transcription

translation

1. Replication

2.Transcription

3.Translation

8.4 Transcription

• RNA differs from DNA in three major ways.

Please add a drawing to each side of your double-bubble map

8.4 Transcription

Protein Synthesis Video

• Replication 1m40s• Transcription 2m50s

8.4 Transcription

• Transcription copies specific genes from DNA to make a strand of RNA.

8.4 Transcription

To transcribe is to make or translate a copy of DNA into RNA

8.4 Transcription

1. RNA polymerase and other proteins, (which we call a transcription complex) recognize the start of a gene and unwind a segment of it.

start site

nucleotides

transcription complex

8.4 Transcription

start site

nucleotides

transcription complex

START Transcription Complex

nucleotides

8.4 Transcription

2. RNA polymerase, using the DNA as a template, strings together a “complementary” strand of RNA•Uracil bonds with Adenine U=A (no Thymine)•The DNA helix winds again as the gene is transcribed.

DNA

RNA polymerase moves along the DNA

RNAWill the RNA be a identical copy of the DNA or a complementary strand?

8.4 Transcription

AAA TAG GAT ATC GGA TAC AGT

UUU AUC CUA UAG CCU AUG UCA

Transcribe this DNA strand into a mRNA strand *Remember: No Thymine. Instead use Uracil. A=U

DNA

RNA

Transcription Practice

8.4 Transcription

3. The RNA strand detaches from the DNA once the gene is transcribed.•DNA rezips

RNA

8.4 Transcription

• Transcription makes three types of RNA.

– Messenger RNA (mRNA) which has been transcribed from the DNA, carries the message that will be translated to form a protein.

– Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made.

– Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome.

8.4 Transcription

growing RNA strands

DNA

onegene

Replication vs. Transcription Double Bubble ( bottom of pg. 6 ) Pg. 242 in book

• Transcription and replication are similar, but have different end results. Please create a double-bubble map comparing and contrasting the two processes.

– Replication copiesall of the DNA

– Transcription copiesa specific gene.

– Replication makesone copy (only happens once)

– Transcription can make many

copies (happens almost continuously)

8.4 Transcription

Similarities between DNA replication and Transcription?

• Occur within the nucleus• Both are catalyzed by enzymes• Both unwind DNA• “complementary” base pairing• Highly regulated (very carefully done- we want NO

mistakes)

8.4 Transcription

Practice

DNA

A T C G A A A T C G G G A T T

RNA

U A G C U U U A G C C C U A A