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DNA, RNA, and Protein
DNA, RNA and Proteins
• Central Dogma:
– DNA codes for RNA which guides protein
synthesis
Nucleus
Gene
• a specific sequence of bases in DNA
that determines the sequence of amino
acids in a protein
Protein
• Proteins contain between
50 - 2000 amino acids
• Very complex structure
– 3 basic shapes:
»Helix
»Pleated sheet
»Globular
Illustration of Protein Structure
Primary
(Amino Acid
Sequence)
Tertiary
(Bending)
Quaternary
(Layering)
Secondary
(Helix)
Pleated Sheets
Hydrogen
Bonds
Structural Proteins
Horn
Fibroin
Hair
Keratin
Spiderweb
Hair
Structure
Hair
Cell
Single hair
Microfibril
Protofibril
|
S
|
S
|
Hydrogen bonds
|
S
|
S
|
disulfide
bridges
Curling of Hair
S
|
|
|
S
|
|
S
S
|
|
|
S
|
S
S
|
|
|
S
|
Permanent
Wave
S
|
Naturally
Curly
Hair
|
S
|
S
|
|
S
Straight
Hair
RNA Structure
• Nucleic acid that
makes protein
Ribonucleic acid
RNA Structure
Shape:
Sugar:
Base:
Size:
Location:
Function:
DNA
• Double Helix
• Deoxyribose
• Thymine
• Very Large
• Nucleus
• Stores
Genetic Info,
replication,
makes RNA
RNA
• Single Helix
• Ribose
• Uracil
• Smaller
• Cytoplasm
• Makes protein
Transcription
• The copying of a
genetic message
from DNA to RNA
RNA
DNA
released
Base
Pairs
to
DNA
half
Original DNA
make
Separate
protein
‘transcribes’
RNA
Transcription
Transcription
RNA Transcription in Action
Three Types of RNA
mRNA
A G A U G C G A G U U A U G G
codons
Ribosome
contains rRNA
Met Amino
acid
tRNA
anticodon
Large
subunit
1 2
Small
subunit
tRNA
docking
sites
UGA
Messenger RNA (mRNA)
• Carries the
information for
making a protein
from DNA to the
ribosomes.
• Acts as a
template (pattern)
• Contains codons
Codons
• Triplets of bases that code for a particular
amino acid
• Start Codon: (AUG) - marks the start of a
polypeptide
• Stop Codon: (UAA, UAG, UGA) - marks the
end
Ribosomal RNA (rRNA)
• Transcribed in
nucleus and
combined with
protein into
ribosomes (site of
protein synthesis)
Transfer RNA (tRNA)
• Carries amino acid
to specific place on
mRNA
• Contains Anticodon:
– Triplet of bases
complimentary to
mRNA codon
Translation
• protein synthesis
• decoding the
"message" of mRNA
into a protein
Information Flow:
DNA RNA Protein
Gene Regulation and Mutation
What is meant by gene
expression?
• Gene expression refers to genes being
‘turned on’ and producing a product. The
product could be an enzyme, a structural
protein, or a control molecule
Gene Expression
• Prokaryotic cells regulate gene expression
with a set of genes called an operon (also
located in some eukaryotes).
• An operon is a group of closely linked
genes that produces a single mRNA
molecule in transcription and that consists
of structural genes and regulating
elements
Eukaryotic Gene Expression
• Eukaryotic cells regulate gene expression
using various transcription factors and
other processes.
Mutations
• Any change in the
nucleotide sequence
of DNA
• Can occur in any cell
– Somatic (body cell)
Mutations:
• may be harmful but
not inherited
– Gamete (germ cell)
Mutations:
• can be inherited
Causes
•
Mutagens:
–
–
Radiation- UV, Xrays, etc.
Chemicals
(asbestos, etc.)
Single Nucleotide Polymorphism
SNP’s (SNIPS)
• Example:
CAT
HAT
• For a change in DNA
CGT
SNP
CGA
• What Amino Acid is produced for each?
mRNA
GCA
Alanine
GCU
Alanine
Single Nucleotide Polymorphism
SNP’s (SNIPS)
• For a change in DNA
CGT
SNP
GGT
• What Amino Acid is produced for each?
mRNA
GCA
Alanine
CCA
Proline
Frame Shift
Deletions, Additions, Duplications
Additions
THE DOG BIT THE BOY
THE DOGS BIT THE BOY
THE DOG SBI TTH EBO Y
Deletions
THE DOG BIT THE BOY
THE OGB ITT HEB OY
Frame Shift
Deletions, Additions, Duplications
DNA
TAC GGA GAT TAT CCC GAA ACT
mRNA
AUG CCU CUA AUA GGG CUU UGA
Amino Acid Chain
Met Pro Leu Iso Gly Leu Stop
Methionine Proline Leucine Isoleucine Glycine Leucine Stop
Frame Shift
Deletions, Additions, Duplications
Delete
DNA
TAC GGA GAT TAT CCC GAA ACT
TAC GAG ATT ATC CCG AAA CT
mRNA
AUG CUC UAA UAG GGC UUU GA
Amino Acid Chain
Met Leu Stop Stop Gly Phe
Methionine Leucine Stop Stop Glycine Phenylalanine
Chromosomal Mutation
• Change in an entire
chromosome or in
chromosome
number within a
cell
Translocation
• Transfer of a chromosome segment to a
non-homologous chromosome
Normal
Translocation
Inversion
• Rotation of a chromosome segment
Normal
Inversion
Insertion
• Breaking off of a chromosome segment
and attaching to its homologue
Normal
Insertion
Deletion
• Chromosome segment left out
Normal
Deletion
Trinucleotide Polymorphisms
•
•
•
•
•
•
•
THE DOG BIT THE BOY
THE BIG DOG BIT THE BOY (addition)
THE GOD BIT THE BOY (inversion)
THE DOG BIT BOY (deletion)
THE BOY BIT THE DOG (translocation)
THE DOG BIT BIT THE BOY (repetition)
THE DOG BIT THE BOY AND RAN OFF
(expansion)