Download Section 8.4: Transcription

Section 8.4: Transcription
Biology
Objectives
Essential Question: How and why does the DNA code
become RNA?
1. Describe the Central Dogma.
2. What types of RNA exist to help DNA form
proteins?
3. Explain the process of transcription.
4. Compare and contrast replication and
transcription.
Central Dogma
 Information flows in one
direction
DNA
 Three processes:
 Replication: DNA copies
itself
 Transcription: Conversion
of DNA to RNA
 Translation: RNA is
converted into a string of
amino acids
RNA
Protein
Central Dogma
Prokaryotic
 In the cytoplasm:
 replication
 transcription
 translation
Eukaryotic
 In the nucleus:
 replication
 transcription
 In the cytoplasm:
 translation
 RNA must go through
processing before
leaving the nucleus
RNA: Ribonucleic Acid
Types of RNA
 mRNA: messenger RNA
 Intermediate message that allows the movement of
the DNA message from the nucleus to the cytoplasm
 rRNA: ribosomal RNA
 Present on ribosomes, where proteins are made
 tRNA: transfer RNA
 Brings amino acids from the cytoplasm to the
ribosome to assist in making proteins
Process of Transcription
 Process of copying the DNA message into a
complementary RNA strand
 A gene, not a whole chromosome, is transferred into
RNA
 RNA polymerases are used to bind the nucleotides
together to make a new RNA molecule
Transcritpion
1. RNA polymerases recognizes start site on gene


RNA polymerases and proteins assemble on DNA and
unwind it
Produces two separate strands of DNA
2. RNA polymerases uses one DNA strand as a template
 Strings RNA nucleotides together, using the same
nucleotides EXCEPT THIAMINE, WHICH IS REPLACED
BY URACIL
3. Once the RNA polymerase is done, the DNA zips back
up, and mRNA is free to move out of the nucleus once it
has been processed
Transcription &
Replication
Similar
 Occur in the nucleus of the
cell
 Use large, complex
enzymes
 Unwind DNA
 Highly regulated
Dissimilar
 Different products
 Replication allows for
reproduction
 Replication only occurs once
per cell cycle
 Transcription is need to
respond to the environment
 Transcription occurs over
and over in a cell on a
consistent basis