Download Chapter 13 PowerPoint

DNA, RNA, and Proteins
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Students know and understand the
characteristics and structure of living things,
the processes of life, and how living things
interact with each other and their
environment.
Benchmark 3.11: DNA has a general
structure and function and a role in heredity
and protein synthesis.
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Gene
DNA
Nucleotide
Purine
Pyrimidine
DNA replication
DNA helicase
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DNA polymerase
RNA
Gene expression
Transcription
Translation
Codon
Videos approximately
51 minutes.
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DNA is the primary material
that causes recognizable,
inheritable characteristics in
related groups of
organisms.
It’s made of two parallel
strands of linked subunits
called nucleotides.
Each nucleotide is made up
of:
◦ A phosphate group
◦ A 5-carbon sugar molecule
called deoxyribose
◦ A nitrogen-containing base
DNA Jurrasic (2:30)
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Information in DNA is contained in the order
of the bases.
Base-pairing allows information to be copied.
The sugar and phosphate molecules are the
same in every DNA molecule BUT there are
four nitrogenous bases:
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The purines are adenine (A) and guanine (G)
The pyrimidines are thymine (T) and cytosine (C)
They only pair together as:
A—T
and
C—G
or T—A and
G—C
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The genetic code consists of 64 triplets of
nucleotides called codons.
With three exceptions, all of these codons
encodes for one of 20 amino acids.
Example: TTA codes for leucine and ATT
codes for Isoleucine.
The exceptions are the START and STOP
codons.
STOP codons include: TAA, TAG and TGA
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When DNA replicates, it copies itself.
The DNA molecule unwinds, and the two sides
split. Then, new nucleotides are added to each
side until two identical sequences result.
Step 1: Unwind and DNA strands separate to
form Y-shaped replication forks.
Step 2: Add Complementary Bases
Step 3: Formation of Two Identical DNA
Molecules
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DNA helicases unwind
the DNA
DNA polymerases
catalyze the formation
of the DNA molecule at
the replication fork.
They also “proofread” to
make sure the
replication is perfect. If
not, they can go back
and remove the
incorrect nucleotide,
replacing it with the
correct one.
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Prokaryotes usually have a single DNA
molecule or chromosome that is in a closed
loop. Two replication forks begin at a single
site, known as the origin of replication.
Replication occurs in opposite directions until
the forks meet on the other side of the loop.
Eukaryotic cell replication starts at many sites
along the chromosome.
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Transcription
occurs at the first
stage of gene
expression where
the genetic
information is
transferred from
the DNA to the
RNA.
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Translation occurs
as the second stage
of gene expression
when the RNA
translates
information to form
specific proteins.
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RNA is ribonucleic
acid.
It is usually a single
strand.
Nucleotides contain
5-carbon sugar,
ribose rather than
deoxyribose.
Instead of thymine, it
has the nitrogenous
base, uracil.
Uracil (U) with
adenine (A).
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Messenger RNA (mRNA) is
the type of RNA produced
when DNA is transcribed
into RNA.
It carries instructions for
making a protein from a
gene.
Like DNA, each 3nucleotide sequence is
called a codon which is
matched to 1 of 20 amino
acids.
The genetic code is based
on codons that represent a
specific amino acid.
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START codon: AUG
STOP codons: UAA, UGA
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Transfer RNA (tRNA) reads
the mRNA sequence then
turns it into a specific
sequence of protein
subunits called amino
acids.
It decodes and matches the
amino acid sequences and
places them on growing
chains of proteins.
One end of tRNA is an
amino acid, the other end
has an anticodon which is a
3-nucleotide sequence
complementary to an mRNA
codon.
Here’s how it works
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Protein production
takes place on the
ribosomes which are
made up of about 80
protein molecules and
several large RNA
molecules. rRNA is
found on the
ribosomes.
In eukaryotic cells,
where are the
ribosomes attached and
what does that
organelle do to the new
proteins?
2:00 minutes