Transcript Searching for the “Secret of Life”

DNA to PROTEIN
 2 step process of transcription and translation
Protein Synthesis:
>Transcription & Translation
 DNA contains all the information for your
traits – in the form of genes
 These genes are blueprints and need to
remain safe – kept inside the nucleus
 Copies can be made through – a messenger
 Form proteins (polymers) from the building
blocks – amino acids (monomers)
Genotype  Phenotype
(genetic)
(observable)
DNA mRNA tRNA PROTEIN
Transcription
Translation
Transcription – making mRNA from
DNA in the nucleus
 mRNA – stands for messenger RNA


it is the copy of the DNA message for making
a protein
Occurs in the nucleus only
Transcription
Section 12-3
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
Transcription
DNA
RNA
A
U
(Steps)
 DNA “unzips” – helicases

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
separate DNA molecule
Free-floating RNA w/in the
nucleus attach to
T
complementary DNA base
pairs
C
Covalent bonds form b/w
sugar-phosphate
backbone
C
mRNA is released
DNA zips back up
A
G
G
mRNA
 Transcribes DNA message and carries it to
ribosomes
 RNA polymerase is the enzyme that matches up
the base pairs
 No T (thymine) so when it reads the nucleotide A
on DNA it matches it with U (Uracil).
CLICK ON
PICTURE FOR
ANIMATION ON
TRANSCRIPTION
Translation – using mRNA and tRNA
to make proteins
 Ribosomes are the site
of protein synthesis
mRNA base tRNA base
codon
anticodon
A
U
U
A
C
G
G
C
 Click here to see mRNA
and tRNA work together
at that ribosome to build
a protein
Codon = 3 mRNA nucleotides (bases)
Anti-codon = 3 tRNA nucleotides (bases)
3 bases code for 1 specific amino acid
Concept Map
Section 12-3
RNA
can be
Messenger RNA
also called
Ribosomal
RNA
which functions to
mRNA
also called
which functions to
rRNA
Combine
with proteins
Carry
instructions
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer
RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
Review – by now you should know…
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structure of DNA
How DNA replicates
Differences b/w DNA & RNA
Steps of Transcription & Translation
Parts of tRNA
3 types of RNA
Translation
Section 12-3
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Phenylalanine
Methionine
tRNA
Ribosome
mRNA
Go to
Section:
Start codon
Lysine
mRNA
Mutation – permanent change in DNA
 Important:
Germ-cell
 source of new variation Mutations
important for evolution.
 Causes:
 viruses, high temps,
chemicals, radiation
Occurs in
gametes
Somatic-cell
Mutations
Occurs in body
cells
Don’t affect
Affects
organism, but
organism itself
affects offspring
Ex: skin cancer,
leukemia
2 categories of mutations
 1) Gene mutations – may involve large
segments of DNA or a single nucleotide
 2) Chromosome mutations – either changes
in the structure of a chromosome or loss or
gain of an entire chromosome
Gene Mutations
(large segments or a single nucleotide)
 Point mutations:
change in 1
nitrogen base

*Can do 1 of 3 things*
 Change a.a. being coded
for the protein
 Change a.a. to a start
and stop codon
 Not change the a.a. or
http://www.intelihealth.com/i/P/PointMutationGEN.gif
the protein at all
 Example: sickle cell
anemia
Gene Mutations
(large segments or a single nucleotide)
 Frameshift mutation:
addition or deletion of a
nitrogen base


Changes EVERY triplet &
a.a. after the insertion or
deletion of a nitrogen base
More severe since more
a.a. are affected
http
://kvhs.nbed.nb.ca/gallant/biology/point_mutations.jpg
http://staff.jccc.net/PDECELL/evolution/mutations/mutypes.gif
Chromosomal Mutations
Section 12-4
Deletion
Insertion/
Duplication
Inversion
Translocation
Chromosome mutations – either changes in the
structure of a chromosome or loss or gain of an entire chromosome
 Inversion: chromosome segment breaks off and
then reattaches in reverse orientation to the
same chr
 Translocation: chr segment breaks off and
attaches to different chr

Causes sterility in plants
Chromosome mutations – either changes in the
structure of a chromosome or loss or gain of an entire chromosome
 Deletion: loss of a piece of chr due to chr
breakage
 Nondisjunction: a pair of homologous chr or
single chr fails to separate during meiosis

2 kinds of gametes result

1) trisomy (extra chr…3 homologous chr’s )
 Down Syndrome (trisomy 21)

2) monosomy (missing a chr…1 homologous chr
instead of 2)
 Ex: Turner’s Syndrome (X monosomy)
Nondisjunction-Chromosome mutation
Nondisjunction – Chr mutation
http://www.biology.iupui.edu/biocourses/N100H/images/11nondisjunction.gif