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DNA and Protein Synthesis-REPEAT
• DNA contains 4 bases. They are:
•Adenine (A)-pairs with Thymine only
•Thymine (T)-Pairs with adenine only
•Guanine (G)-pairs with cytosine only
•Cytosine (C)-pairs with guanine only
•DNA contains the genetic information to
make amino acids
• Amino acids combine to make proteins
• These proteins determine the physical traits
of an organism and control cellular functions.
• Proteins do everything,
and DNA gets all the
credit!
• Think of them as tiny minions
who do all the work
DNA and Protein Synthesis
• Codon: three bases code for a specific protein:
ex: AAA = Lysine
• The codons code for 20 amino acids
• Just like the alphabet has 26 letters to make all
the words we know, the 20 amino acids make
all the different proteins found in living
organisms
•This makes it possible to have 64 different
combinations for amino acids
• The codons are the template for protein synthesis
•Protein synthesis is the production of protein
which takes place on the ribosomes in the
cytoplasm
**Protein is very important because it triggers
many cell processes as we learned earlier
DNA and Protein Synthesis
But… How does the
information get from the
DNA to the cytoplasm?
mRNA
RNA
1. DNA must be decoded to
work
2. The structure of RNA is
similar to DNA but has 3
differences
a. Sugar in RNA is Ribose
b. RNA is single-stranded
c. Uracil replaces thymine
3. Three main types of RNA
a. Messenger RNA (mRNA)-This
contains instructions for joining
amino acids to make proteins; three
consecutive nucleotides make up a
codon (a single amino acid). The
complimentary trio is an anticodon
b. Ribosomal RNA (rRNA)Assembles proteins into ribosomes
c. Transfer RNA (tRNA)-carries each
amino acid to the ribosome
according to a coded message from
mRNA
RNA Concept Map
Section 12-3
RNA
can be
Messenger RNA
also called
mRNA
Ribosomal RNA
which functions to
also called
Carry instructions
rRNA
which functions to
Combine
with proteins
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer RNA
also called
tRNA
which functions to
Bring
amino acids to
ribosome
4. Transcription-The process of copying
DNA into RNA (for decoding of DNA)
making it possible for a gene in DNA to
be copied hundreds of times
a. The DNA strands separate or “unzip”)
b. Nucleotides of RNA match up and join
the DNA strand-they are creating
mRNA
**Bases pair up the same way except
uracil binds with adenine instead of
thymine
c. The completed RNA strand is
released and moves into the
cytoplasm
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Adenine (DNA and RNA)
Guanine(DNA and RNA)
Cystosine (DNA and RNA)
Thymine (DNA only)
Guanine(DNA and RNA)
Uracil (RNA only)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
DNA and Protein Synthesis
Practice making mRNA using the DNA template
A T T A C A
C U A A U G U
mRNA
5. 5. Translation -RNA is a molecule that
contains instructions for making proteins.
This process occurs on the ribosome.
a. mRNA moves into the cytoplasm and
attaches to a ribosome (rRNA)
b. The rRNA decodes the message and sends
out tRNA to pick up an amino acid
c. Each codon has an anticodon brought in
by tRNA to compliments or pair up (CGA
pairs with GCU) forming bonds (like puzzle
pieces)
d. tRNA breaks away to allow another one to
bring in a new anticodon
e. A long chain is built until a stop codon is
reached (there are three possible types)
Translation
The Genetic Code Wheel
Codons and amino acids: This is the message from
mRNA and is translated by rRNA and it tells tRNA what
amino acid to pick up and add to the protein chain
Name the Amino
Acid for each
anticodon:
UAU
CCG
AGU
GCA
Tyrosine
Proline
Serine
Alanine
What do you think
the DNA codon
was for these
anticodons?
Journal ; Determining the Sequence of a Gene
DNA contains the code of instructions for cells.
Sometimes, an error occurs when the code is
copied. Such errors are called mutations.
1.Copy the following information about Protein
X: Methionine—Phenylalanine—
Tryptophan—Asparagine—Isoleucine—
STOP.
2.Use the Genetic Code Wheel to determine one
possible sequence of RNA to code for this
information. Write this code below the
description of Protein X. Below this, write the
DNA code that would produce this RNA
sequence.
3.Now, cause a mutation in the gene
sequence that you just determined by
deleting the fourth base in the DNA
sequence. Write this new sequence.
4.Write the new RNA sequence that would
be produced. Below that, write the amino
acid sequence that would result from this
mutation in your gene. Call this Protein
Y.
5.Did this single deletion cause much
change in your protein? Explain your
answer.
12-4: Mutations
Mutations are changes in the genetic
material.
A. Kinds of Mutations
1. gene mutations-mutations that
produce changes in a single gene
a. point mutations- Gene mutations
involving a change in one or a few
nucleotides that occur at a single
point in the DNA sequence.
1. substitutions-one base
replaces another.
2. Frameshift Mutations
a. The effects of insertions or deletions
are more dramatic.
b. The addition or deletion of a nucleotide
causes a shift in the grouping of codons.
c. Types
1. insertions- an extra base is inserted
into a base sequence
2. deletions- loss of a single base is
deleted and the reading frame is
shifted
3. chromosomal mutations- mutations that
produce changes in the number or structure
of chromosomes.
a. Types
1. Deletion-the loss of all or part of a
chromosome.
2. Duplication- produce extra copies
of parts of a chromosome.
3. Translocation-occurs when part of
one chromosome breaks off and
attaches to another
4. Inversion- reverse the direction of
parts of chromosomes.
B. Significance of Mutations
1. Many mutations have little or no
effect on gene expression.
2. Some mutations are the cause of
genetic disorders.
3. Beneficial mutations may produce
proteins with new or altered
activities that can be useful.
Example: Polyploidy is the condition
in which an organism has extra sets
of chromosome