Download 8.4 Transcription

8.4 Transcription
KEY CONCEPT
Transcription converts a gene
into a single-stranded RNA
molecule.
NEW VOCABULARY
(Def. on next 2 slides)
Central Dogma
RNA
Transcription
RNA Polymerase
Messenger RNA (mRNA)
Ribosomal RNA (rDNA)
Transfer RNA (tRNA)
MAIN IDEAS
1.
2.
3.
8.4 Transcription
NEW VOCABULARY
• Central Dogma
• A theory that states, in cells, information flows in one direction:
from DNA
RNA
proteins.
• RNA
• Nucleic acid molecule that allows for the transmission of genetic information and
protein synthesis.
• You can think of RNA as a temporary copy of DNA that is used, then
destroyed.
• Transcription
• The process of copying a sequence of DNA to produce a complementary strand of
messenger RNA.
8.4 Transcription
VOCABULARY CONTINUED…
• RNA Polymerase
• Enzyme that catalyzes the synthesis of a complementary strand of RNA
from a DNA template.
• Enzymes that bond nucleotides together in a chain to make a new
RNA molecule.
• Messenger RNA (mRNA)
• Form of RNA that carries genetic information from the nucleus to the
cytoplasm, where it serves as a template for protein synthesis.
• Ribosomal RNA (rDNA)
• RNA that is in the ribosome & guides the translation of mRNA into a
protein.
• Forms part of the ribosomes = cell’s protein factories.
• Transfer RNA (tRNA)
• Form of the RNA that brings amino acids to ribosomes during protein
synthesis.
8.4 Transcription
Main Idea #1: 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
replication
– Translation
transcription
• RNA is a link between
DNA and proteins.
translation
8.4 Transcription
• RNA differs from DNA in three major ways.
– RNA has a ribose sugar NOT a deoxyribose sugar.
– Because it has one more oxygen atom.
– RNA has the base uracil instead of the base thymine.
– RNA is a single-stranded structure.
– Remember DNA is a double stranded structure.
8.4 Transcription
Main Idea #2: Transcription makes three types of RNA.
• Transcription copies DNA to make a strand of RNA.
• Transcription is catalyzed by RNA polymerase.
• RNA polymerase and other proteins form a
transcription complex.
• The transcription complex recognizes the start of a
gene and unwinds a segment of it.
start site
transcription complex
nucleotides
8.4 Transcription
– Nucleotides pair with one strand of the DNA.
– RNA polymerase bonds the nucleotides together.
– The DNA helix winds again as the gene is transcribed.
DNA
RNA polymerase
moves along the DNA
8.4 Transcription
– The RNA strand detaches from the DNA once the gene
is transcribed.
RNA
8.4 Transcription
• Transcription makes three types of RNA.
– Messenger RNA (mRNA) 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
Main Idea #3
The transcription process is similar to replication.
• Transcription and replication both involve complex
enzymes and complementary base pairing.
• The two processes have different end results.
– Replication copies
all the DNA;
transcription copies
one
gene
growing RNA strands
a gene.
– Replication makes
one copy;
DNA
transcription can
make many copies.