Download From DNA to RNA

From Nucleotide Sequence to
Amino Acid Sequence
• The language of nucleic acids will be
translated into the language of amino acids
• What is the
language of
nucleic acids?
DNA molecule
Gene 1
Gene 2
Gene 3
DNA strand
Transcription
RNA
Translation
Codon
Polypeptide
Amino acid
• When DNA is transcribed the
result is an RNA molecule
• RNA is then translated into a sequence
of amino acids in a polypeptide
• Triplets of bases
– are called codons and they
specify all the amino acids
The Genetic Code – our translating dictionary
• The genetic code is the set of rules translating
nucleotide sequence to amino acid sequence
• The genetic code
is shared by
all organisms
Transcription: From DNA to RNA
• In transcription
– genetic information is copied from DNA to RNA
– RNA molecule is transcribed from a DNA template
RNA nucleotides
RNA
polymerase
Newly made
RNA
(a) A close-up view of transcription
Direction of
transcription
Template
strand of DNA
Three Phases of Transcription
• The “start transcribing” signal is a
nucleotide sequence called a promoter
• The first phase of transcription is Initiation
• The second phase of transcription is Elongation
• The third phase of transcription is Termination
Translation: The Players
• Translation
– conversion from the nucleic acid
language to the protein language
Messenger RNA (mRNA)
• mRNA
– message sent from the DNA in the nucleus
out into the cytoplasm, to the ribosomes
Transfer RNA (tRNA)
• tRNA
– carries
amino acids
– matches codons
with anticodons
Amino acid attachment site
Hydrogen bond
RNA
polynucleotide
chain
Anticodon
Anticodon
Ribosomes
• Ribosomes
– organelles that
make proteins
– made of two
protein subunits
tRNA
binding sites
Large
subunit
mRNA
binding
site
Small
subunit
(a)
P site
P
A site
A
Translation: The Process
• Translation is divided into three phases
– Initiation
– Elongation
– Termination
• A fully
assembled
ribosome holds
tRNA and
mRNA for use
in translation
Next amino acid
to be added to
polypeptide
Growing
polypeptide
tRNA
mRNA
Review: DNA RNA Protein
• The flow of genetic information in a cell
CHAPTER 11 – DNA TECHNOLOGY
• The DNA of two people of the
same sex is over 99% identical
• Animals, plants, and bacteria
can be genetically modified to
produce human proteins
BIOLOGY AND SOCIETY:
HUNTING FOR GENES
• DNA technology has created many advances
– Genetically Modified (GM) food
– DNA fingerprinting
– Human Genome Project
RECOMBINANT DNA TECHNOLOGY
• Recombinant DNA is combining genes
from different sources; GM organism
From Medicine to Food
• Put a gene into a bacterium and its proteins
can be produced in large quantities
Making Humulin
• Humulin, 1982
• DNA technology develops vaccines
– a vaccine is a
harmless version
of a pathogen
Genetically Modified (GM) Foods
• DNA technology replaces plant-breeding programs
– half of
American
crops of
soybeans and
corn are GM
• GM corn; insects
• “Golden rice” has been genetically modified
to contain beta-carotene; Vitamin A
“Pharm” Animals
• GM animals are less common; sheep with a
human blood protein for cystic fibrosis
Recombinant DNA Techniques
• Bacteria are the workhorses
• Biologists use bacterial plasmids
– small, circular DNA molecules
• Plasmids easily incorporate foreign DNA
– they act as vectors, carriers that move genes
Cell containing gene
of interest
Host cell
1
DNA
Recombinant DNA
(host DNA plus
gene of interest)
2
Gene of
interest
Cell multiplies and
produces protein
3
Genes may be inserted
into another organism
Protein may be harvested
OR
Gene for pest resistance
inserted into plants
Protein dissolves blood clots
in heart attack therapy