Download 12–3 RNA and Protein Synthesis

12–3 RNA and Protein Synthesis
12–3 RNA and Protein
Synthesis
Genes are DNA instructions that control the
production of proteins or polypeptide chain--a chain
of amino acids.
--sections of DNA that act as a code/set of
instructions for making proteins
Genetic messages can be decoded by copying part
of the nucleotide sequence from DNA into RNA.
So why copy the DNA?
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12–3 RNA and Protein Synthesis
If DNA is the code for making proteins why can’t it be “read” by
the ribosome.
HINT: JOURNAL QUESTION FROM YESTERDAY…
•DNA can’t leave the nucleus because it
•Is too big.
•DNA is the instructions for building every protein; cells only
need to make the proteins for that type of cell
•Enzymes will break it down if detected outside the nucleus.
•THEREFORE MSUST HAVE A WAY FOR MESSAGE TO
LEAVE
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12–3 RNA and Protein Synthesis
The Structure of RNA
The Structure of RNA
RNA consists of a long chain of nucleotides.
Each nucleotide is made up of a 5-carbon sugar, a
phosphate group, and a nitrogenous base.
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12–3 RNA and Protein Synthesis
The Structure of RNA
There are three main differences between RNA and
DNA:
• The sugar in RNA is ribose instead of
deoxyribose.
• RNA is generally single-stranded and shorter.
• RNA contains uracil in place of thymine.
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12–3 RNA and Protein Synthesis
Types of RNA
Messenger RNA (mRNA) carries copies of
instructions for assembling amino acids into proteins.
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12–3 RNA and Protein Synthesis
Transcription
What is transcription?
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12–3 RNA and Protein Synthesis
Transcription
Transcription
RNA molecules are produced by copying part of a
nucleotide sequence of DNA into a complementary
sequence in RNA. This process is called
transcription.
Transcription requires another enzyme, RNA
polymerase.
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12–3 RNA and Protein Synthesis
Transcription
During transcription, RNA polymerase
binds to DNA and separates the DNA
strands.
RNA polymerase then uses one strand
of DNA as a template from which
nucleotides are assembled into a strand
of RNA.
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12–3 RNA and Protein Synthesis
Transcription
RNA polymerase binds only to regions of DNA known
as promoters.
Promoters are signals in DNA that indicate to the
enzyme where to bind and which side of the DNA
to bind to in order to make to make RNA.
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12–3 RNA and Protein Synthesis
Transcription
RNA
RNA polymerase
DNA
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12–3 RNA and Protein Synthesis
Translation
Messenger RNA is
transcribed in the nucleus,
and then enters the cytoplasm
where it attaches to a
ribosome and is translated
into a protein.
Nucleus
mRNA
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12–3 RNA and Protein Synthesis
Codon
The sequence of
bases in DNA is used
as a template for
mRNA.
Genes and Proteins
Codon Codon
Single strand of DNA
Codon Codon Codon
The codons of mRNA
specify the sequence
of amino acids in a
protein.
mRNA
Alanine Arginine Leucine
Amino acids within
a polypeptide
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The role of a master plan in a building is similar
to the role of which molecule?
a. messenger RNA
b. DNA
c. transfer RNA
d. ribosomal RNA
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12–3
A base that is present in RNA but NOT in DNA is
a. thymine.
b. uracil.
c. cytosine.
d. adenine.
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12–3
A region of a DNA molecule that indicates to an
enzyme where to bind to make RNA is the
a. intron.
b. exon.
c. promoter.
d. codon.
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A codon typically carries sufficient information to
specify a(an)
a. single base pair in RNA.
b. single amino acid.
c. entire protein.
d. single base pair in DNA.
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END OF SECTION