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RNA
(Ribonucleic Acid)
How is RNA different from DNA?
Lets Review DNA
 What sugar does it have?
 Adenine pairs with ___________
 Cytosine pairs with __________
 Double or single stranded?
RNA is different from DNA
 RNA contains the sugar
RIBOSE
 Uracil substitute for Thymine
(A pairs with U)
 Single stranded
DNA TO RNA
DNA=ATTGCAC
RNA=UAACGUG
RNA? Who cares?
 Why is RNA important?
 It contains the code from
DNA that is needed to make
proteins!
Three types of RNA
 Messenger RNA (mRNA)
 Code from DNA  takes
the code from the nucleus
into the cytoplasm then to
the ribosome.
 Transfer RNA (tRNA)
 Transfers amino acids
from the cytoplasm to
the ribosomes.
 Ribosomal RNA (rRNA)
 Part of the ribosome, links
up proteins
Protein Synthesis
(The making of proteins)
 2 steps in Protein synthesis
 Transcription
 Translation
Transcription
 mRNA copies the code from DNA, and travels through
cytoplasm to ribosome where it sticks.
Let’s Do Transcription!
DNA=
A G CT GA
mRNA= U C G A C U
Codons
 Three nitrogen bases.
 Codons code for the genetic
code!
 Each amino acid is coded for
by 3 mRNA bases
 If you string a bunch of amino
acids together, what do you
get??
1 CODON = 1 AMINO ACID = 3 NUCLEOTIDES
Translation
 Translates the mRNA into amino acids.
 Ribosomes attach to the mRNA strand
 tRNA picks up amino acids in the cytoplasm and carries
them to the ribosomes (where mRNA is stuck).
 tRNA contains the anticodon that complements the codon on
the mRNA
Translation: The Details
What are codons
again??
 1. mRNA strand leaves the nucleus, enters cytoplasm,
attaches to ribosome.
2. tRNA molecules pick up amino acids
in cytoplam and carries them to
ribosomes
3. tRNA anticodon pairs with mRNA
codon, joining the two molecules
4. Once an amino acid has joined
the chain, the tRNA leaves.
5. The process continues until a chain of
amino acids is formed and stops once a
stop codon on the mRNA is reached.
Translation
DNA
=A T G C T A
mRNA = U A
C G A U
(Codon)
tRNA = A U G C U A
(Anticodon)
TRANSCRIPTION
Takes place in the
nucleus
translation
Moves out of nucleus
into the cytoplasm &
attach to ribosome
Steps to figure out the genetic code
1. Obtain a DNA Template. (a row of DNA bases)
2. Transcribe DNA into mRNA
3. Use the codons (mRNA) to translate into amino
acids
let’s practice!
DNA
TAC
mRNA (Codon)
AUG
tRNA Strand
(anticodon)
UAC
Amino Acids
Start
More practice needed?
DNA=
TAC -GAT-GCC-ATC
mRNA=
AUG -CUA- CGG-UAG
tRNA=
UAC -GAU-GCC-AUC
Amino Acids=
START-LEU-ARG-STOP
MUTATIONS
 Change in the genetic code
 May occur in the genes or the chromosomes
 ONLY MUTATIONS IN GAMETES MAY BE PASSED TO
OFFSPRING.
 Two types:
 Point
 Frameshift
Point Mutations (in the genes)
 Only change a few nucleotides
 Examples:
 Substitution – one base is changed to another
 Insertion – a base is added to the gene
 Deletion – a base is removed from the gene
Frame-shift Mutations (in the genes)
 Change the reading frame
 Examples:
Chromosomal Mutations
 Change the number or structure of the chromosomes
 Examples:
 Deletion – losing all or part of the chromosome
 Duplication – extra copies of parts of the chromosome
 Inversion – reversing the order of the pieces of the
chromosome
 Translocation – pieces of chromosomes break off and stick to
another chromosome
Significance of Mutation
 Some mutations are neutral – not good, not bad.
 Mutations that change the specific proteins needed are
usually harmful
 Some mutations are good! Like those of your who now can
digest lactose.