Transcript Document

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
•SetTranscription
up Cornell Notes on
pg. 7
8.4 Transcription
2.1 Atoms, Ions,
and Molecules
•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?
KEY CONCEPT
Transcription converts a
gene into a singlestranded RNA molecule.
3.2 Cell Organelles
REVIEW:
rough endoplasmic
reticulum
Have bumps called
ribosomes which
link amino acids together
to form
proteins
8.4 Transcription
Proteins are used for movement, eyesight,
and digestion and practically everything
else you do.
8.4 Transcription
Review: Replication
nucleotide
nucleotides
Helicase
unzips
8.4 Transcription
2. DNA polymerase (pol-uh-mer-ase)
enzymes bond the nucleotides together to
form the new double helix.
complementary
new strand
nucleotide
DNA polymerase
8.4 Transcription
3. Two
new molecules of DNA are formed,
each with an original “parent” strand and a
complementary newly formed “daughter”
complementary
strand.
original strand
new strand
Two molecules of DNA
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.
1. Replication
2.Transcription
3.Translation
replication
transcription
• RNA is a link between
DNA and proteins.
translation
8.4 Transcription
• RNA differs from DNA in three major ways.
RNA
Ribose Sugar
Uracil (U)
Single-Stranded
Please add a
drawing to each
side of your
double-bubble
map
DNA
Deoxyribose Sugar
Thymine (T)
Double-Stranded
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.
transcription complex
start site
nucleotides
8.4 Transcription
Transcription Complex
transcription complex
START
start site
nucleotides
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.
Will the RNA be a
identical copy of the
DNA or a
complementary
strand?
RNA
DNA
RNA polymerase
moves along the DNA
8.4 Transcription
Transcription Practice
Transcribe this DNA strand into a mRNA strand
*Remember: No Thymine. Instead use Uracil. A=U
DNA
AAA TAG GAT ATC GGA TAC AGT
RNA
UUU AUC CUA UAG CCU AUG UCA
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.
vs. Transcription Double Bubble ( bottom of
8.4Replication
Transcription
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 copies
all of the DNA
– Transcription copies
a specific gene.
one
gene
– Replication makes
one copy (only happens once)
– Transcription can make many
copies (happens almost continuously)
growing RNA strands
DNA
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