Transcript Protein Synthesis PowerPoint

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Objectives
• Compare the structure of RNA with that of DNA.
• Summarize the process of transcription.
• Relate the role of codons to the sequence of amino
acids that results after translation.
• Outline the major steps of translation.
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Structure of a Nucleotide
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DNA
Abbreviation
stands for…
# of strands
RNA
deoxyribonucleic acid
ribonucleic acid
double strand
single strand
Type of sugar
deoxyribose
ribose
4 nitrogen base
present
adenine, thymine,
cytosine, guanine
adenine, uracil,
cytosine, guanine
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Pairing Between Bases
• base-pairing rules in DNA
– adenine always pairs with a thymine
– guanine always pairs with a cytosine
complementary
– The strictness of base-pairing results in two strands that
contain complementary base pairs.
• base-pairing rules in RNA
– adenine always pairs with a uracil
– guanine always pairs with a cytosine
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3 Types of RNA
mRNA – messenger RNA; a single
stranded RNA molecule that
contains the codon information to
make a protein
rRNA – ribosomal RNA; RNA
molecules that make up the
ribosome protein factories
tRNA – transfer RNA; single
strand of RNA that contains the
anticodon and temporarily carry
a specific amino acid on one end
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Chapter 10
Section 1 From Genes to Proteins
Types of RNA
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Chapter 10
Section 1 From Genes to Proteins
Codons in mRNA
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Chapter 10
Section 1 From Genes to Proteins
Ribosomes
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Chapter 10
Section 1 From Genes to Proteins
tRNA and Anticodon
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Listing of 20 amino acids
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Codes in mRNA
possible codon combos:
4 x __
4 x __
4 = 64
__
1. CGG
2. UAU
3. AUG
4. UGA
methionine
codon = made up of triplets
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• transcription  the instructions for making a
protein are transferred from a gene to an
messenger RNA molecule
DNA  mRNA
• translation  portion of protein synthesis
that takes place at ribosomes and uses
the codons in mRNA molecules to specify the
sequence of amino acids in protein chains
mRNA  protein
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• gene expression  the entire process by which
proteins are made based on the information encoded
in DNA. aka protein synthesis.
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Transfer of Information from DNA to RNA
• transcription  1st step in the making of a protein
– takes the information found in a gene in the
DNA and transfers it to a molecule of RNA.
– transcribe DNA into mRNA
• RNA polymerase  an enzyme that adds and links
complementary RNA nucleotides during transcription,
is required.
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C G
U A
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Snapshot of Translation
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Mutations
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Mutations
• gene rearrangements  mutations that move an
entire gene to a new location
– Changes in a gene’s position often disrupt the
gene’s function because the gene is exposed to
new regulatory controls in its new location.
• Genes sometimes move as part of a transposon.
Other times, the portion of the chromosome
containing a gene may be rearranged during meiosis.
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gene rearrangements  mutations that move an entire
gene to a new location
• aka chromosome mutation
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Mutations
•
Mutations that change a gene  gene alterations.
1. point mutation  a single nucleotide changes.
A. missense point mutation
B. silent point mutation
C. nonsense mutation
2. frameshift mutation  reading frame of codon changes
or “shift”
A. insertion frameshift mutation
B. deletion frameshift mutation
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missense point mutation  occurs when one nitrogen
base is substituted for another nitrogen base causing a
different amino acid than previously to occur in the
protein sequence.
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silent point mutation  Happens when one base in a
codon is changed but both code for the same amino
acid.
Silent b/c there are more than
one codon for each amino
acid.
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nonsense point mutation  A base mutation that
creates a new stop codon in place of an amino acid
causing a premature stopping of translation
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Mutations
• Because the genetic message is read as a series of
triplet nucleotides, insertions and deletions of one or
two nucleotides can upset the triplet groupings.
• frameshift mutation  A mutation that causes a gene
to be read in the wrong three-nucleotide sequence
delete
cysteine - valine
methionine - cysteine
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Insertion frameshift mutation  shifts the reading
frame to the right.
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Deletion frameshift mutation  shifts the reading
frame to the left.
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Major Types of Mutations
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Types of Gene Mutations
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