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RNA = RiboNucleic Acid
Structure of RNA
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Single stranded
Ribose Sugar
Phosphate group
Base: Adenine, Uracil, Cytosine, Guanine
Three Types of RNA
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Messenger RNA (mRNA) – transfers DNA
code to ribosomes for translation.
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Transfer RNA (tRNA) – brings amino
acids to ribosomes for protein synthesis.
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Ribosomal RNA (rRNA) – Ribosomes are
made of rRNA and protein.
Transcription
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RNA molecules are produced by copying
part of the nucleotide sequence of DNA
into complementary sequence in RNA, a
process called transcription.
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During transcription, RNA polymerase
binds to DNA and separates the DNA
strands.
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RNA polymerase then uses one strand of
DNA as a template from which
nucleotides are assembled into a strand of
mRNA.
mRNA
The Genetic Code
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“Words” are 3 RNA sequences called codons.
aaacgttcgccc
DNA sequence
Complimentary mRNA
codons
Amino
acids
uuugcaagcggg
uuu-gca-agc-ggg
Lysine – Arginine – Serine - Proline
Genetic Codes: Codon Chart
Translation
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During translation, the cell uses
information from messenger RNA to
produce proteins.
1.Transcription
occurs in nucleus.
2.mRNA
moves to the cytoplasm then to the
ribosomes. tRNA “read” the mRNA and
obtain the amino acid coded for.
3.Ribosomes
attach amino acids together
using a peptide bond, forming a
polypeptide chain.
4.Polypeptide
chain keeps growing until a
stop codon is reached, creating a protein.
Translation to Protein
Mutations
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Mutations are changes in the DNA code.
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Gene mutations result from changes in a
single gene.
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Chromosomal mutations involve changes
whole chromosomes.
Gene Mutation
Gene Mutation
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Point Mutation – Affect one nucleotide
thus occurring at a single point on the
gene. Usually one nucleotide is
substituted for another nucleotide.
Gene Mutation
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Frameshift Mutation – Inserting an extra
nucleotide or deleting a nucleotide
causes the entire code to “shift”.
Mutations
More Mutations
Gene Regulation

All (with a few exceptions) of an organism’s
cells have the same DNA. Why then are
there different cells?

The gene expression is different. In other
words, cells ‘differentiate’ by expression of
some genes and suppression of others.
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Cells respond to their environment by
producing different types and amounts of
protein. Can you think of a situation where
this might happen?
Gene Regulation: Producing Proteins
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Injury repair: cells can adapt to
environmental changes such as an injury
which requires repair by activating new
genes
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Cancer is a disease of uncontrolled and
invasive cell reproduction. Cancers result
when the genes responsible for coding the
proteins that regulate cell division mutate
and divide rapidly.
Complete the Chart
Questions
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Which base in RNA is replaced by uracil?
How many mRNA codons are illustrated on
the previous slide?
What is the name of the enzyme that
creates the mRNA copy from DNA?
What is the name of the sugar in the
mRNA nucleotides?
What is the mRNA transcript for the DNA
sequence, TTACGC
Complete the Chart
Questions
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What structure assists tRNA in translating
the mRNA in the cytoplasm?
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The role of tRNA is to carry a(n):
Gene Regulation
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In simple cells (prokaryotic) lac genes
which are controlled by stimuli, turn genes
on and off.
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In complex cells (eukaryotic) this process
is not as simple. Promoter sequences
regulate gene operation.
How Does it Work?
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RNA Polymerase looks for a region on the
DNA known as a promoter, where it binds
and begins transcription.
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RNA strands are then edited. Some parts
are removed (introns) - which are not
expressed – and other that are left are
called exons or expressed genes.
Chromosomal Mutations
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Deletion – Part of a chromosome is
deleted
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Duplication – part of a chromosome is
duplicated
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Inversion – chromosome twists and
inverts the code.
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Translocation – Genetic information is
traded between nonhomologous
chromosomes.
Chromosomal Mutations