Download Chapter 10

How Proteins are
Made
How RNA differs from DNA
1st- RNA consists
of a single
strand of
nucleotides
instead of the 2
strands found in
DNA
RNA
DNA
How RNA differs from DNA
2nd- RNA
nucleotides One less Oxygen
contain the fivecarbon sugar
ribose rather
than the sugar
deoxyribose
found in DNA
How RNA differs from DNA
3rd- RNA has
A, C, G, and UUracil (U bonds
with A because no
T in RNA)
Example: DNA ATGCATCG
RNA UACGUAGC
Transcription and Translation

The instruction for
making a protein
are transferred
from a gene to an
RNA molecule in a
process called
transcription.
Transcription and Translation
Cells then use 2
different types of RNA
to read the
instructions on the
RNA molecule and put
together the amino
acids that make up
the protein in a
process called
translation.
Transcription: Making RNA
Step 1: Transcription
begins when RNA
polymerases bind to
the gene’s promoter
(a specific sequence of
DNA that acts as a
“start” signal for
transcription.
Transcription: Making RNA

Step 2: RNA
polymerases then
unwind and
separate the 2
strands of the
double helix,
exposing the DNA
nucleotides on
each strand.
Transcription: Making RNA

Step 3: RNA
polymerase adds
and then links
complementary RNA
nucleotides as it
“reads” the gene.
Transcription
Messenger RNA
(mRNA) is a form of
RNA that carries the
instructions for making
a protein from a
gene and delivers it
to the site of
translation.
http://10.11.3.62/videos/The%20Language%20of%20Life%20Understandin
g%20the%20Genetic%20Code/sec7268_300k.asf
Gene Regulation
and Structure

In eukaryotes, many genes are
interrupted by introns (long
segments of nucleotides that have
no coding information.
Gene Regulation
and Structure
 Exons
are the
portions of a
gene that are
translated
(expressed) into
proteins.
Gene Regulation and
Structure
The exons that remain
are “stitched” back
together by the
spliceosomes to
form a smaller mRNA
molecule that is then
translated.
Transcripton & Codons


The RNA instructions are written as a
series of three-nucleotide sequences on
the mRNA called codons.
Example: UAU UGU AGG
Codes for: Tyrosine Cysteine Arginine
mRNA Codon Chart
****EOC QUESTIONS****
A short chain of DNA has the
nucleotide sequence ATA CCG. Its
complementary mRNA nucleotide
sequence is
A. TAT GCC
C. TUT GCC
B. UAU GCC
D. UAU GGC
****EOC QUESTIONS****
What is the maximum number of amino
acids that could be coded for by a
section of mRNA with the sequence
GUCCAGAACUGU?
A. 3
B. 4
C. 6
D. 12
****EOC QUESTIONS****
If a codon reads UGU, what is its
anticodon?
A. TCT
B. AGA
C. UGU
D. ACA
****EOC QUESTIONS****
What is the name of the amino acid
coded by AGU?
Serine
___________________
Translation: Assembling
Proteins
 Transfer
RNA
(tRNA) molecules
are single strands
of RNA that
temporarily carry a
specific amino acid
on one end.
Translation: Assembling
Proteins

An anticodon is a threenucleotide sequence on a tRNA that
is complementary to an mRNA
codon.
Translation: Assembling
Proteins
 Ribosomal RNA (rRNA)
molecules are RNA molecules that
are part of the structure of
ribosomes.
Steps of Translation


Step 1: The ribosomal subunits, the
mRNA, and the tRNA carrying
methionine bind together.
Step 2: The tRNA carrying the amino
acid specified by the codon in the A
site arrives.
Steps of Translation


Step 3: A peptide bond forms
between adjacent amino acids.
Step 4: The tRNA in the P site
detaches and leaves its amino acid
behind.
Steps of Translation


Step 5: The tRNA in the A site
moves to the P site, the tRNA
carrying the amino acid specified by
the codon in the A site arrives.
Step 6: A peptide bond is formed.
The tRNA in the P site detaches and
leaves its amino acid behind.
Steps of Translation

Step 7: The process is repeated until
a stop codon is reached. The
ribosomes complex falls apart. The
newly made protein is released.
http://10.11.3.62/videos/The%20Language%20of%20Life%20Understand
ing%20the%20Genetic%20Code/sec7269_300k.asf
EOC Test Prep
1. Which cellular
function does this
model represent?
A. Transcription
B. Translation
C. Transformation
D. DNA replication
EOC Test Prep
2. Which part of the
model represents a
codon?
F. A
G. BCodons
***
are
H. associated
C
with mRNA
J. D
EOC Test Prep
3.What does the part
labeled E represent?
A. Ribosome
The circles
represent amino
acids which are
what proteins are
made up of.
B. Growing protein
chain
C. Messenger RNA
D. Transfer RNA
Practice
DNA- A C C T G T A A C G A G C C A G T T
mRNA- U G G A C A U U G C U C G G U C A A
tRNA- A C C U G U A A C G A G C C A G U U
6
Codon - _____
Amino Acid-
Tryp Thre Leu Leu Glyc