Download Unit 7a * Structure of DNA

Unit 7c – Protein Synthesis (Part 1)
Transcription
Chapter 8.4 & 8.5
The Making of a Protein
• Proteins are made in the cell
• DNA carries genetic information, which includes
all the codes for every protein
• Protein is made in the cytoplasm
▫ How? DNA gives the code to RNA, RNA delivers
information
RNA carries DNA’s instructions.
• The central dogma
states that
information flows
in one direction
from DNA to RNA
to proteins.
•
Protein Synthesis includes three processes.
– Replication
– Transcription
– Translation
•
RNA is a link between DNA and
proteins.
replication
transcription
translation
What is RNA?
•
Ribonucleic Acid
RNA differs from DNA in three major ways.
– RNA has a ribose sugar instead of deoxyribose
– RNA has uracil instead of thymine.
– RNA is a single-stranded structure.
Transcription makes RNA inside the nucleus
• Transcription copies DNA to make a strand of RNA.
▫ 1st – Replication must occur
 The section of DNA that carries the code will open up
-- 2nd – Free nucleotides find their buddies and makes an
RNA strand
-- 3rd – DNA section will close back together
Transcription in a little more detail
•
RNA polymerase is the enzyme that helps make RNA.
– 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
– The RNA strand detaches from the DNA once the gene
is transcribed.
RNA
Transcription in a little more detail
•
There are 3 types of RNA.
– Messenger RNA (mRNA) carries the message that will be translated to form
a protein. (From nucleus to cytoplasm)
– Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome.
(in the cytoplasm)
– Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made.
(at the ribosome)
Transcription vs. Replication
• SAME: they both have complex enzymes and
complementary base pairing.
• DIFFERENT:
▫ Replication copies
all the DNA;
transcription copies
a gene.
▫ Replication makes
one copy;
transcription can
make many copies.
one
gen
e
growing RNA strands
DNA
• http://www.youtube.com/watch?v=ztPkv7wc3yU