8.4 Transcription•Set up Cornell Notes on pg. 5

•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.

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?

8.4 Transcription

P.4Draw fig 8.10 (pg.239)- color code

Make a double-bubble map comparing and contrasting DNA and RNA (239-240)

• Red • Blue • Green

On Your OWN: The Central Dogma

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

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

RNA

DNA

8.4 Transcription

Connect• Suppose you want to play skeeball at a arcade. The

game only takes tokens, but you only have quarters. What do you do?– You exchange your quarters for tokens.

• In a similar way, your cells cannot make proteins from DNA.

• They must convert the DNA into RNA in order to make proteins

• This process is known as transcription

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.

replication

transcription

translation

1. Replication• Copies DNA

2.Transcription• Converts DNA into

RNA• RNA is a link

between DNA and proteins

• “quarters tokens”

3.Translation• Interprets an RNA

message into a string of amino acids that will make up a protein

8.4 Transcription

• Protein Synthesis: the process whereby biological cells generate new proteins. Includes DNA replication, transcription, and translation.

8.4 Transcription

Location of Protein Synthesis

• Prokaryotic cells: replication, transcription, and translation all occur in the cytoplasm (remember there is no nucleus), at approx the same time

• In Eukaryotic cells, where DNA is located inside the nucleus, these processes are separated by location and times. – Replication and transcription occur in the nucleus– Translation occurs in the cytoplasm

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

• RNA is similar to DNA in a few ways– Both are a chain of nucleotides– Each is made of a sugar, a phosphate group, and a

nitrogen containing base– Each has A, C, & G

8.4 Transcription

Protein Synthesis Video

• Transcription 2m50s

8.4 Transcription

• Transcription copies specific genes from DNA to make a complementary strand of RNA.– Only a gene, NOT the entire DNA strand is transcribed

8.4 Transcription

To transcribe is to make a copy of DNA into a complementary messenger RNA strand

8.4 Transcription

Get out 3 Colors and MAKE A KEY on the top of your handout

-DNA

-RNA

- Transcription Complex (RNA Polymerase)

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

Why must the DNA strands unwind and separate before transcription can take place?–The bases must be exposed so that the DNA can be read

start site

nucleotides

transcription complex

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

RNA

8.4 Transcription

How does the base sequence of the RNA transcript being formed compare with the sequence on the template strand?•It is complementary

DNA

RNA polymerase moves along the DNA

RNA

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.•The transcription complex falls apart•DNA re-zips

RNA

8.4 Transcription

Where will the RNA transcript go after it separates from the DNA in step 3?•It is processed and LEAVES the nucleus, heads to the cytoplasm

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

Please make a Replication vs. Transcription Double Bubble (bottom of pg. 4) 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)

Differences?• End results are different• Replication makes an identical copy of ALL of the DNA

• Happens only once during the cell cycle• Transcription only makes a complementary strand of segments

of DNA• Can happen over and over again at anytime

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